NEET-2016 allotment list (after 1st Counseling)

Neet2016 1st Counseling results are out..
Cutoff rank
MBBS (UR) 4733
(OBC) 4781
(SC) 30020
(ST) 53031
MBBS (UR-PH) 160789
(SC-PH) 362248
(ST-PH) 366239
BDS (UR) 7579
(OBC) 7589
(SC) 38204
(ST) 67190
BDS. (UR-PH) 180514
(SC-PH) 347251
(ST-PH) 329022

To download result file, click on the following link

Round 1 Allotment

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NEET – SEAT MATRIX

cbse has published no. of seats of colleges available under 15% AI quota.

please click on the following link to view and download.

MBBS SEAT MATRIX

BDS seat matrix

seat matrix of all colleges are available in excel sheet below..

MBBS Course Institute, Category After Adding new Vacancy (ALL CATEGORY)

MBBS Course Institute, Category After Adding new Vacancy (UR CATEGORY)

MBBS Course Institute, Category After Adding new Vacancy (UR(PH) CATEGORY)

MBBS Course Institute, Category After Adding new Vacancy (OBC CATEGORY)

MBBS Course Institute, Category After Adding new Vacancy (SC CATEGORY)

MBBS Course Institute, Category After Adding new Vacancy (ST CATEGORY)

AIPMT 2015 COUNSELLING – FINAL ALLOTMENT LIST

Congratulations all for your performance in NEET-2016..

Now when ranks are out you must be wondering whether you will get your desired college or not.

For this check last year allotment list for 15% all india quota. It will give you a rough idea of your chances of getting a particular college.

Click on the following link to download last year allotment file..

AIPMT2015-ROUND-III-ALLOTMENT

NEET Phase-II (24-07-2016) Biology Solution {Code – XX}

NEET Phase-II Biology solution

Code – XX

Date – 24-07-2016

 

  1. A foreign DNA and plasmid cut by the samerestriction endonuclease can be joined toform a recombinant plasmid using
    1. ligase
    2. Eco RI
    3. Taq polymerase
    4. polymerase III

Ans.        (1) Ligase                                                                              [NCERT class 12, page 197]      

 

  1. Which of the following is not a component ofdownstream processing?
    1. Expression
    2. Separation
    3. Purification
    4. Preservation

Ans.        (1) Expression                                                  [NCERT class 12, page 205]

 

  1. Which of the following restriction enzymesproduces blunt ends?
    1. Hind III
    2. Sal I
    3. Eco RV
    4. Xho I

Ans.        (3) Eco RV

 

  1. Which kind of therapy was given in 1990 to afour-year-old girl with adenosine deaminase(ADA) deficiency?
    1. Radiation therapy
    2. Gene therapy
    3. Chemotherapy
    4. Immunotherapy

Ans.        (2) Gene therapy                                                                      [NCERT class 12, page 211]

 

  1. How many hot spots of biodiversity in theworld have been identified till date byNorman Myers?
    1. 43
    2. 17
    3. 25
    4. 34

Ans.        (4) 34                                                                            [NCERT class 12, page 266]

 

  1. The primary producers of the deep-seahydrothermal vent ecosystem are
    1. coral reefs
    2. green algae
    3. chemosynthetic bacteria
    4. blue-green algae

Ans.        (3) chemosynthetic bacteria                                             [NCERT class 12, page 226]

  

  1. Which of the following is correct forr-selected species?
    1. Small number of progeny with large size
    2. Large number of progeny with small size
    3. Large number of progeny with large size
    4. Small number of progeny with small size

Ans.        (2) Large number of progeny with small size

 

  1. If’+’ sign is assigned to beneficial interaction, ‘-’ sign to detrimental and ‘0’ sign to neutralinteraction, then the population interactionrepresented by ‘+’ refers to
    1. parasitism
    2. mutualism
    3. amensalism
    4. commensalism

Ans.        (1) parasitism                                                [NCERT class 12, page 232]

 

  1. Which of the following is correctly matched?
    1. Stratification—Population
    2. Aerenchyma—Opuntia
    3. Age pyramid—Biome
    4. Parthenium hysterophorus—Threat to biodiversity

Ans.        (4) Parthenium hysterophorus—Threat to biodiversity                                        [NCERT class 12, page 265]

 

  1. Red List contains data or information on
    1. marine vertebrates only
    2. all economically important plant
    3. plants whose products are ininternational trade
    4. threatened species

Ans.        (4) threatened species                                                           [NCERT class 12, page 263]

 

  1. Which one of the following is wrongfor fungi?
    1. They are both unicellular and
    2. They are eukaryotic.
    3. All fungi possess a purely cellulosic cell wall.
    4. They are heterotrophic

Ans.        (3) All fungi possess a purely cellulosic cell wall                                                        [NCERT class 11, page 22]

 

  1. Methanogens belong to
    1. Slime moulds
    2. Eubacteria
    3. Archaebacteria
    4. Dinoflagellates

Ans.        (3) Archaebacteria                                                             [NCERT class 11, page 19]

 

  1. Select thewrong
    1. Diatoms are microscopic and floatpassively in water.
    2. The walls of diatoms are easily
    3. ‘Diatomaceous earth’ is formed by thecell walls of diatoms.
    4. Diatoms are chief producers in the

Ans.        (2) The walls of diatoms are easily destructible.            [NCERT class 11, page 20]

 

 

  1. The label of a herbarium sheetdoes not carry information on
    1. height of the plant
    2. date of collections
    3. name of collector
    4. local names

Ans.        (1) height of the plant                                                           [NCERT class 11, page 12]

 

  1. Conifers are adapted to tolerate extremeenvironmental conditions because of
    1. presence of vessels
    2. broad hardy leaves
    3. superficial stomata
    4. thick cuticle

Ans.        (4) thick cuticle                                                              [NCERT class 11, page 38]

 

  1. which one of the following statements iswrong?
    1. Laminaria and Sargassum are used as
    2. Algae increase the level of dissolved oxygen in the immediate environment.
    3. Algin is obtained from red algae, andcarrageenan from brown algae.
    4. Agar-agar is obtained from Gelidium and

Ans.        (3) Algin is obtained from red algae, and carrageenan from brown algae   [NCERT class 11, page 32]

 

  1. The term ‘polyadelphous’ is related to
    1. calyx
    2. gynoecium
    3. androecium
    4. corolla

Ans.        (3) androecium                                                                   [NCERT class 11, page 75]

 

  1. How many plants among, indigophera, Sesbania, Salvia, Allium, Aloe, Mustard, Groundnut, Radish, Gram, and Turnip have stamens with different lengths in their flowers?
    1. six
    2. Three
    3. Four
    4. Five

Ans.        (3) Four (Salvia, Mustard, Radish, Turnip)              [NCERT class 11, page 75]

 

  1. Radial symmetry is found in the flowers of
    1. Cassia
    2. Brassica
    3. Trifolium
    4. Pisum

Ans.        (2) Brassica                                                              [NCERT class 11, page 72,79]

 

  1. Free-central placentation is found in
    1. Citrus
    2. Dianthus
    3. Argemone
    4. Brassica

Ans.        (2) Dianthus                                                                      [NCERT class 11, page 75]

 

 

  1. Cortex is the region found between
    1. endodermis and vascular bundle
    2. epidermis and stele
    3. pericycle and endodermis
    4. endodermis and pith

Ans.        (2) epidermis and stele                                              [NCERT class 11, page 91]

 

  1. The balloon-shaped structures called tyloses
    1. are linked to the ascent of sap through xylem vessels
    2. originate in the lumen of vessels
    3. Characterize the sapwood
    4. are extensions of xylem parenchyma cells into vessels

Ans.        (4) are extensions of xylem parenchyma cells into vessels

 

  1. A non-proteinaceous enzyme is
    1. deoxyribonuclease
    2. lysozyme
    3. ribozyme
    4. ligase

Ans.        (3) ribozyme                                                                    [NCERT class 11, page 154]

 

  1. Select the
    1. Methanogens—Prokaryote
    2. Gas vacuoles—Green bacteria
    3. Large central vacuoles—Animal cells
    4. Protists—Eukaryotes

Ans.        (3) Large central vacuoles—Animal cells            [NCERT class 11, page 129]

 

  1. Select the wrong
    1. Mycoplasma is a wall-less
    2. Bacterial cell wall is made up of
    3. Pili and fimbriae are mainly involved inmotility of bacterial cells.
    4. Cyanobacteria lack flagellated cells.

Ans.        (3) Pili and fimbriae are mainly involved in motility of bacterial cells           [NCERT class 11, page 129]

 

  1. A cell organelle containing hydrolyticenzymes is
    1. mesosome
    2. lysosome
    3. microsome
    4. ribosome

Ans.        (2) lysosomes                                                                  [NCERT class 11, page 134]

 

  1. During cell growth, DNA synthesis takesplace in
    1. M phase
    2. S phase
    3. G1 phase
    4. G2 phase

Ans.        (2) S phase                                                                        [NCERT class 11, page 163]

 

 

  1. Which of the following biomolecules iscommon to respiration-mediated breakdownof fats, carbohydrates and proteins?
    1. Acetyl CoA
    2. Glucose-6-phosphate
    3. Fructose 1,6-bisphosphate
    4. Pyruvic acid

Ans.        (1) Acetyl CoA                                                                 [NCERT class 11, page 236]

 

  1. A few drops of sap were collected by cuttingacross a plant stem by a suitable method.The sap was tested chemically. Which one ofthe following test results indicates that it isphloem sap?
    1. Absence of sugar
    2. Acidic
    3. Alkaline
    4. Low refractive index

Ans.        (3) Alkaline

 

  1. You are given a tissue with its potential fordifferentiation in an artificial culture. Whichof the following pairs of hormones would youadd to the medium to secure shoots as wellas roots?
    1. Gibberellin and abscisic acid
    2. IAA and gibberellins
    3. Auxin and cytokinin
    4. Auxin and abscisic acid

Ans.        (3) Auxin and cytokinin                                              [NCERT class 12, page 177]

 

  1. Phytochrome is a
    1. Chromoprotein
    2. Flavoprotein
    3. Glycoprotein
    4. Lipoprotein

Ans.        (1) Chromoprotein

 

  1. Which is essential for the growth of root tip?
    1. Mn
    2. Zn
    3. Fe
    4. Ca

Ans.        (2) Zn                                                                    [NCERT class 11, page 198,248]

 

  1. The process which makes major differencebetween C3 and C4 plants is
    1. respiration
    2. glycolysis
    3. Calvin cycle
    4. Photorespiration

Ans.        (4) Photorespiration                                                 [NCERT class 11, page 220]

 

  1. Which one of the following statements is not correct?
    1. Water hyacinth, growing in the standingwater, drains oxygen from water thatleads to the death of fishes.
    2. Offspring produced by the asexualreproduction are called clone.
    3. Microscopic, motile asexual reproductivestructures are called zoospores.
    4. In potato, banana and ginger, theplantlets arise from the internodespresent in the modified stem.

Ans.        (4) In potato, banana and ginger, the plantlets arise from the internodes present in the modified stem.                                                                                                                                                                        [NCERT class 12, page 8]

 

  1. Which one of the following generates newgenetic combinations leading to variation?
    1. Nucellar polyembryony
    2. Vegetative reproduction
    3. Parthenogenesis
    4. Sexual reproduction

Ans.        (4) Sexual reproduction                                             [NCERT class 12, page 38]

 

  1. Match Column—I with Column—II andselect the correct option using the codesgiven below:
  Column—I   Column—II
a. Pistils fused together (i) Gametogenesis
b. Formation of gametes (ii) Pistillate
c. Hyphae of higher Ascomycetes (iii) Syncarpous
d. Unisexual female flower (iv) Dikaryotic

Codes :

a             b              c                 d 

  1. (iii)            (i)            (iv)          (ii)
  2. (iv)             (iii)          (i)            (ii)
  3. (ii)            (i)            (iv)          (iii)
  4. (i)               (ii)           (iv)          (iii)

Ans.        (1) a-(iii), b-(i), c-(iv), d-(ii)                                        [NCERT class 11, page 23,75]

 

  1. In majority of angiosperms
    1. a small central cell is present in theembryo sac
    2. egg has a filiform apparatus
    3. there are numerous antipodal cells
    4. reduction division occurs in themegaspore mother cells

Ans.        (4) reduction division occurs in the megaspore mother cells                               [NCERT class 12, page 26,27]

 

  1. Pollination in water hyacinth and water lily isbrought about by the agency of
    1. Bats
    2. Water
    3. insects or wind
    4. birds

Ans.     (3) insects or wind                                                                                                [NCERT class 12, page 29]

 

  1. The ovule of an angiosperm is technicallyequivalent to
    1. megaspore
    2. megasporangium
    3. megasporophyll
    4. megaspore mother cell

Ans.     (2) megasporangium                                               [NCERT class 12, page 25]

 

  1. Taylor conducted the experiments to provesemiconservative mode of chromosomereplication on
    1. coli
    2. Vinca rosea
    3. Vicia faba
    4. Drosophila melanogaster

Ans.     (3) Vicia faba                                                              [NCERT class 12, page 106]

 

  1. The mechanism that causes a gene to movefrom one linkage group to another is called
    1. crossing-over
    2. inversion
    3. duplication
    4. translocation

Ans.     (4) translocation

 

  1. The equivalent of a structural gene is
    1. recon
    2. muton
    3. cistron
    4. operon

Ans.     (3) Cistron                                                                    [NCERT class 12, page 109]

 

  1. A true breeding plant is
    1. always homozygous recessive in itsgenetic constitution
    2. one that is able to breed on its own
    3. produced due to cross-pollination amongunrelated plant
    4. near homozygous and produces offspringof its own kind

Ans.     (4) near homozygous and produces offspring of its own kind                   [NCERT class 12, page 70]

 

  1. Which of the following rRNAs acts asstructural RNA as well as ribozyme inbacteria?
    1. 8 S rRNA
    2. 5 S rRNA
    3. 18 S rRNA
    4. 23 S rRNA

Ans.     (4) 23 S rRNA                                                                              [NCERT class 12, page 115]

 

  1. Stirred-tank bioreactors have been designedfor
    1. ensuring anaerobic conditions in theculture vessel
    2. purification of product
    3. addition of preservatives to the product
    4. availability of oxygen throughout theprocess

Ans.     (4) availability of oxygen throughout the process                                      [NCERT class 12, page 204]

 

  1. A molecule that can act as a genetic materialmust fulfill the traits given below, except
    1. it should provide the scope for slow changes that are required for evolution
    2. it should be able to express itself in theform of ‘Mendelian characters’
    3. it should be able to generate its replica
    4. it should be unstable structurally andchemically

Ans.     (4) it should be unstable structurally and chemically                         [NCERT class 12, page 103]

 

  1. DNA-dependent RNA polymerase catalyzestranscription on one strand of the DNAwhich is called the
    1. antistrand
    2. template strand
    3. coding strand
    4. alpha strand

Ans.     (2) template strand                                                  [NCERT class 12, page 108]

 

  1. Interspecific hybridization is the mating of
    1. more closely related individuals withinsame breed for 4-6 generations
    2. animals within same breed withouthaving common ancestors
    3. two different related species
    4. superior males and females of differentbreeds

Ans.     (3) two different related species                                         [NCERT class 12, page 168]

 

  1. which of the following is correctregardingAIDS causative agent HIV?
    1. HIV does not escape but attacks theacquired immune response.
    2. HIV is enveloped virus containing onemolecule of single-stranded RNA and onemolecule of reverse transcriptase.
    3. HIV is enveloped virus that contains twoidentical molecules of single-stranded RNA and two molecules of reverse
    4. HIV is unenveloped retrovirus.

Ans.     (3) HIV is enveloped virus that contains two identical molecules of single-stranded RNA and two molecules of reverse transcriptase                                                                

 

  1. Among the following edible fishes, whichone is a marine fish having rich source ofomega-3 fatty acids?
    1. Mackerel
    2. Mystus
    3. Mangur
    4. Mrigala

Ans.     (1) Mackerel                                                                  [NCERT class 12, page 169]

 

  1. Match Column—I with Column—II and select the correct option using the codesgiven below:

Column—I                              Column—II

  1. Citric acid                                (i)    Trichoderma
  2. Cyclosporin A                         (ii)   Clostridium
  3. Statins                                    (iii) Aspergillus
  4. Butyric acid                           (iv) Monascus

Codes :

a          b         c          d

  1. (iii)      (iv)     (i)        (ii)
  2. (iii)        (i)        (ii)       (iv)
  3. (iii)        (i)        (iv)     (ii)
  4. (i)          (iv)     (ii)       (iii)

Ans.     (3) a-(iii), b-(i), c-(iv), d-(ii)                                              [NCERT class 12, page 183]

 

  1. Biochemical Oxygen Demand (BOD) may not be a good index for pollution for water bodiesreceiving effluents from.
    1. sugar industry
    2. domestic sewage
    3. dairy industry
    4. petroleum industry

Ans.     (4) petroleum industry                                                          [NCERT class 12, page 276]

 

  1. The principle of competitive exclusion wasstated by
    1. Verhulst and Pearl
    2. Darwin
    3. F. Gause
    4. MacArthur

Ans.     (3) G. F. Gause                                                           [NCERT class 12, page 234]

 

  1. Which of the following National Parks is home to the famous musk deer or hangul?
    1. Dachigam National Park, Jammu &Kashmir
    2. Keibul Lamjao National Park, Manipur
    3. Bandhavgarh National Park, MadhyaPradesh
    4. Eaglenest Wildlife Sanctuary, ArunachalPradesh

Ans.     (1) Dachigam National Park, Jammu & Kashmir                                                  

 

  1. A lake which is rich in organic waste mayresult in
    1. mortality of fish due to lack of oxygen
    2. increased population of aquaticorganisms due to minerals
    3. drying of the lake due to algal bloon
    4. increased population of fish due to lots ofnutrients

Ans.     (1) mortality of fish due to lack of oxygen                        [NCERT class 12, page 275]

 

  1. The highest DDT concentration in aquaticfood chain shall occur in
    1. eel
    2. phytoplankton
    3. seagull
    4. crab

Ans.     (3) seagull                                                                [NCERT class 12, page 276]

 

  1. Which-of the following sets of diseases iscaused by bacteria?
    1. Herpes and influenza
    2. Cholera and tetanus
    3. Typhoid and smallpox
    4. Tetanus and mumps

Ans.     (2) Cholera and tetanus                                               [NCERT class 11, page 26]

 

 

  1. Match Column—I with Column—II forhousefly classification and select the correctoption using the codes given below :

Column—I                      Column—II

  1. Family                   (i)   Diptera
  2. order                      (ii) Arthropoda
  3. Class                 (iii)  Muscidae
  4. Phylum                   (iv) Insecta

Codes :

a      b    c  d

  1.          (iv)    (ii)       (i)        (iii)
  2.         (iii)    (i)        (iv)      (ii)
  3.        (iii)     (ii)       (iv)      (i)
  4.       (iv)      (iii)      (ii)       (i)

Ans.     (2) a-(iii), b-(i), c-(iv), d-(ii).                                       [NCERT class 11, page 11]

 

  1. Choose the correct
    1. All Pisces have gills covered by an
    2. All mammals are viviparous.
    3. All cyclostomes do not possess jaws and paired fins.
    4. All reptiles have a three-chambered

Ans.     (3) All cyclostomes do not possess jaws and paired fins                      [NCERT class 11, page 56-59]

 

  1. Study the four statements (A-D) given belowand select the two correct ones out of them:
    1. Definition of biological species was givenby Ernst Mayr.
    2. Photoperiod does not affect reproductionin plants.
    3. Binomial nomenclature system wasgiven by R. H.
    4. In unicellular organisms, reproduction issynonymous with growth.

The two correctstatements are

(1) A and B                              (2) B and C                              (3) C and D                      (4) A and D

Ans.     (4) A and D                                                            [NCERT class 11, page 2-7]

 

  1. In male cockroaches, sperms are stored in which part of the reproductive system?
    1. Vas deferens
    2. Seminal vesicles
    3. Mushroom glands
    4. Testes

Ans.     (2) Seminal vesicles                                                                 [NCERT class 11, page 114]

 

  1. Smooth muscles are
    1. voluntary, spindle-shaped, uninucleate
    2. involuntary, fusiform, non-striated
    3. voluntry, multinucleate, cylindrical
    4. involuntary, cylindrical, striated

Ans.     (2) involuntary, fusiform, non-striated                    [NCERT class 11, page 105,303]

 

 

  1. Oxidative phosphorylation is
    1. formation of ATP by energy released from electrons removed during substrateoxidation
    2. formation of ATP by transfer ofphosphate group from a substrateto ADP
    3. oxidation of phosphate group in ATP
    4. addition of phosphate group to ATP

Ans.     (1) formation of ATP by energy released from electrons removed during substrate oxidation                                                                        [NCERT class 11, page 233]

 

  1. Which of the following is the least likely to beinvolved in stabilizing the three-dimensionalfolding of most proteins?
    1. Ester bonds
    2. Hydrogen bonds
    3. Electrostatic interaction
    4. Hydrophobic interaction

Ans.     (1) Ester bonds                                                 [NCERT class 11, page 150]

 

  1. Which of the following describes the given graph correctly?

1

  1. Exothermic reaction with energy A inabsence of enzyme and B in presence ofenzyme
  2. Endothermic reaction with energy A inpresence of enzyme and B in absence ofenzyme
  3. Exothermic reaction with energy A inpresence of enzyme and B in absence ofenzyme
  4. Endothermic reaction with energy A inabsence of enzyme and B in presence ofenzyme

Ans.     (3) Exothermic reaction with energy A in presence of enzyme and B in absence of enzyme                                                                                       [NCERT class 11, page 156]

 

  1. When cell has stalled DNA replication fork,which checkpoint should be predominantlyactivated?
    1. Both G2/M and M
    2. G1/S
    3. G2/M
    4. M

Ans.     (2) G1/S                                                                         [NCERT class 11, page 164]

 

  1. Match the stages of meiosis in Column—I to their characteristic features in Column—II and select the correct option using the codes given below:
  Column—I   Column—II
a. Pachytene (i) Pairing of homologous chromosomes
b. Metaphase-I (ii) Terminalization of chiasmata
c. Diakinesis (iii) Crossing-over takes place
d. Zygotene (iv) Chromosomes align at equatorial plate

a          b         c          d

  1. (iv) (iii)      (ii)       (i)
  2. (iii) (iv)     (ii)       (i)
  3. (i) (iv)     (ii)       (iii)
  4. (ii) (iv)     (iii)      (i)

Ans.     (2) a-(iii), b-(iv), c-(ii), d-(i)                               [NCERT class 11, page 168]

 

  1. Which hormones do stimulate theproduction of pancreatic juice andbicarbonate?
    1. Insulin and glucagon
    2. Angiotensin and epinephrine
    3. Gastrin and insulin
    4. Cholecystokinin and secretin

Ans.     (4) Cholecystokinin and secretin                             [NCERT class 11, page 338]

 

  1. The partial pressure of oxygen in the alveoliof the lungs is
    1. less than that of carbon dioxide
    2. equal to that in the blood
    3. more than that in the blood
    4. less than that in the blood

Ans.     (3) more than that in the blood                                        [NCERT class 11, page 272]

 

  1. Choose the correct
    1. Receptors do not produce graded
    2. Nociceptors respond to changes in
    3. Meissner’s corpuscles are thermo­receptors.
    4. Photoreceptors in the human eye aredepolarized during darkness and becomehyperpolarized in response to the light

Ans.     (4) Photoreceptors in the human eye are depolarized during darkness and become hyperpolarized in response to the light stimulus.                          

 

  1. Graves’ disease is caused due to
    1. hypersecretion of adrenal gland
    2. hyposecretion of thyroid gland
    3. hypersecretion of thyroid gland
    4. hyposecretion of adrenal gland

Ans.     (3) hypersecretion of thyroid gland                                

 

 

  1. Name the ion responsible for unmasking ofactive sites for myosin for cross-bridgeactivity during muscle contraction.
    1. Potassium
    2. Calcium
    3. Magnesium
    4. Sodium

Ans.     (2) Calcium                                                     [NCERT class 11, page 307]

 

  1. Name the blood cells, whose reduction innumber can cause clotting disorder, leadingto excessive loss of blood from the
    1. Thrombocytes
    2. Erythrocytes
    3. Leucocytes
    4. Neutrophils

Ans.     (1) Thrombocyte                                                                   [NCERT class 11, page 280]

 

  1. Name a peptide hormone which acts mainlyon hepatocytes, adipocytes and enhancescellular glucose uptake and utilization.
    1. Gastrin
    2. Insulin
    3. Glucagon
    4. Secretin

Ans.     (2) Insulin                                                                   [NCERT class 11, page 336]

 

  1. Osteoporosis, an age-related disease ofskeletal system, may occur due to
    1. accumulation of uric acid leading toinflammation of joints
    2. immune disorder affecting neuro­muscular junction leading to fatigue
    3. high concentration of Ca++ and Na+
    4. decreased level of estrogen

Ans.     (4) decreased level of estrogen                                [NCERT class 11, page 312]

 

  1. Serum differs from blood in.
    1. lacking antibodies
    2. lacking globulins
    3. lacking albumins
    4. lacking clotting factors

Ans.     (4) lacking clotting factors                                          [NCERT class 11, page 279]

 

  1. Lungs do not collapse between breaths andsome air always remains in the lungs whichcan never be expelled because
    1. pressure in the lungs is higher than theatmospheric pressure.
    2. there is a negative pressure in the lungs
    3. there is a negative intrapleural pressure pulling at the lung walls
    4. there is a positive intrapleural pressure

Ans.     (3) there is a negative intrapleural pressure pulling at the lung walls       

 

  1. The posterior pituitary gland is nota trueendocrine gland because
    1. it secretes enzymes
    2. it is provided with a duct
    3. only stores and releases hormones
    4. it is under the regulation of hypo­thalamus

Ans.     (3) only stores and releases hormones                           [NCERT class 11, page 332]

 

  1. The part of nephron involved in activereabsorption of sodium is
    1. descending limb of Henle’s loop
    2. distal convoluted tubule
    3. proximal convoluted tubule
    4. Bowman’s capsule

Ans.     (3) proximal convoluted tubule                     [NCERT class 11, page 294]

 

  1. Which of the following is hormone-releasing IUD?
    1. Cu7
    2. LNG-20
    3. Multiload 375
    4. Lippes loop

Ans.     (2) LNG-20                                                                [NCERT class 12, page 60]

 

  1. Which of the following is incorrectregarding vasectomy?
    1. Irreversible sterility
    2. No sperm occurs in seminal fluid
    3. No sperm occurs in epididymis
    4. Vasa deferentia is cut and tied.

Ans.     (3) No sperm occurs in epididymis                                   [NCERT class 12, page 62]

 

  1. Embryo with more than 16 blastomeresformed due to in vitro fertilization istransferred into
    1. cervix
    2. uterus
    3. fallopian tube
    4. fimbriae

Ans.     (2) Uterus                                                                 [NCERT class 12, page 64]

 

  1. Which of the following depicts the correct pathway of transport of sperms?
    1. Efferent ductules →Rete testis → Vasdeferens → Epididymis
    2. Rete testis →Efferent ductules→ Epididymis → Vas deferens
    3. Rete testis → Epididymis → Efferentductules → Vas deferens
    4. Rete testis → Vas deferens → Efferentductules → Epididymis

Ans.     (2) Rete testis → Efferent ductules → Epididymis → Vas deferens             [NCERT class 12, page 43]

 

  1. Match Column—I with Column—II andselect the correct option using the codesgiven below :

ColumnI                              ColumnII

  1. Mons pubis (i)    Embryo formation
  2. Antrum (ii)   Sperm
  3. Trophectoderm (iii)  Female external genitalia
  4. Nebenkern (iv) Graafian follicle

Codes :

a          b        c          d

  1. (i) (iv)     (iii)      (ii)
  2. (iii) (iv)     (ii)       (i)
  3. (iii) (iv)     (i)        (ii)
  4. (iii) (i)        (iv)     (ii)

Ans.     (3) a-(iii), b-(iv), c-(i), d-(ii)                                 [NCERT class 12, page 46,48]

 

  1. Several hormones like hCG, hPL, estrogenprogesterone are produced by
    1. pituitary
    2. ovary
    3. placenta
    4. fallopian tube

Ans.     (3) placenta                                           [NCERT class 12, page 53]

 

  1. If a colour-blind man marries a woman whois homozygous for normal colour vision, the probability of their son being colour-blind is

(1) 1 (2)  0                                          (3)  5                              (4)  0.75

Ans.     (2) 0                                                                                   

 

  1. Genetic drift operates in
    1. slow reproductive population
    2. small isolated population
    3. large isolated population
    4. non-reproductive population

Ans.     (2) small isolated population                                               [NCERT class 12, page 137]

 

  1. In Hardy-Weinberg equation, the frequentof heterozygous individual is represented by-

(1) q2 (2) p2                                                              (3) 2pq                              (4) pq

Ans.     (3) 2pq                                                                               [NCERT class 12, page 137]

 

  1. The chronological order of human evolution/ from early to the recent is
    1. Australopithecus → Homo habilis → Ramapithecus → Homo erectus
    2. Australopithecus → Ramapithecus → Homo habilis → Homo erectus
    3. Ramapithecus → Australopithecus → Homo habilis → Homo erectus
    4. Ramapithecus → Homo habilis → Australopithecus → Homo erectus

Ans.     (3) Ramapithecus → Australopithecus → Homo habilis → Homo erectus  [NCERT class 12, page 140]

 

  1. Which of the following is the correct sequence of events in the origin of life?

I- Formation of protobionts

II-Synthesis of organic monomers

III-Synthesis of organic polymers

IV-Formation of DNA-based genetic system

  1. II, III, IV, I
  2. I, II, III, IV
  3. I, III, II, IV
  4. ll, III, I, IV

Ans.     (4) ll, III, I, IV                                                                             [NCERT class 12, page 127]

 

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NEET Phase 2 2016 Solution Set XX

 

CHAPTER 10 – CELL CYCLE AND CELL DIVISION

CELL CYCLE AND CELL DIVISION

  • Growth and reproduction are characteristics of living cells and organisms.

Cell Cycle –

  • The sequence of events by which a cell duplicates its genome, synthesizes the other constituents of the cell and eventually divides into two daughter cells is termed cell cycle.
  • Cell cycle includes three processes cell division, DNA replication and cell growth in coordinated way.
  • Duration of cell cycle can vary from organism to organism and also from cell type to cell type. (e.g., in Yeast cell cycle is of 90 minutes, in human 24 hrs.)

1

Interphase

  • It is divided into 3 further phases G1, S, and G2.

G1 phase (Gap 1 Phase)

  • Corresponds to the interval between mitosis and initiation of DNA replication.
  • During G1 phase the cell is metabolically active and continuously grows but does not replicate its DNA.

S phase (synthesis phase)

  • period during which DNA synthesis or replication takes place.
  • During this time the amount of DNA per cell doubles. (only amount of DNA is doubled, no of chromosomes remain same.)
  • In animal cells, during the S phase, DNA replication begins in the nucleus, and the centriole duplicates in the cytoplasm.

G2 phase (Gap 2 Phase)

  • Proteins are synthesised in preparation for mitosis while cell growth continues.

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  • Some cells do not exhibit division like heart cells, nerve cells etc. these cells enter in an inactive phase called G0 or quiescent phase from G1 phase.
  • Cells in this phase are metabolically active but they do not divide unless they are called on to do so.

Mitosis or M phase

  • In animals, mitotic cell division is only seen in the diploid somatic cells while in the plants mitotic divisions can be seen in both haploid and diploid cells.
  • it is also called as equational division as the number of chromosomes in the parent and progeny cells are the same.
  • Mitosis is divided into the following four stages:
    • Prophase
    • Metaphase
    • Anaphase
    • Telophase

Prophase

  • It follows the S and G2 phases of interphase.
  • The centrioles now begin to move towards opposite poles of the cell.
  • In prophase Chromosomal material condenses to form compact mitotic chromosomes.
  • Initiation of the assembly of mitotic spindle with the help of the microtubules.
  • Cell organelles like Golgi complexes, endoplasmic reticulum, nucleolus and the nuclear envelope disappear.

Metaphase

  • Start of metaphase is marked by the complete disintegration of the nuclear envelope.
  • The chromosomes are spread through the cytoplasm of the cell.
  • condensation of chromosomes is completed and they can be observed clearly under the microscope.
  • This is the stage at which morphology of chromosomes is most easily studied.
  • At this stage, metaphase chromosome is made up of two sister chromatids, which are held together by the centromere.
  • centromere serve as the sites of attachment of spindle fibres to the chromosomes.
  • chromosomes are moved into position at the centre of the cell.
  • the metaphase is characterised by all the chromosomes coming to lie at the equator with one chromatid of each chromosome connected by its kinetochore to spindle fibres from one pole and its sister chromatid connected by its kinetochore to spindle fibres from the opposite pole.
  • The plane of alignment of the chromosomes at metaphase is referred to as the metaphase plate or equatorial plate.

Anaphase

  • At the onset of anaphase, each chromosome arranged at the metaphase plate is split simultaneously and the two daughter chromatids begin to move towards the two opposite poles.
  • As each chromosome moves away from the equatorial plate, the centromere of each chromosome is towards the pole and hence at the leading edge, with the arms of the chromosome trailing behind

Telophase

  • At the beginning of telophase, the chromosomes at their respective poles decondense and form chromatin network.
  • Nuclear envelope assembles around the chromatin network.
  • Nucleolus, Golgi complex and ER etc cell organelles reform.

Cytokinesis

  • After karyokinesis the cell itself is divided into two daughter cells by a separate process called cytokinesis.
  • In an animal cell, this is achieved by the appearance of a furrow in the plasma membrane.
  • The furrow gradually deepens and ultimately joins in the centre dividing the cell cytoplasm into two.
  • Plant cells undergo cytokinesis by cell plate method. In cell plate method wall formation starts in the centre of the cell and grows outward to meet the existing lateral walls.
  • The formation of the new cell wall begins with the formation of a simple precursor, called the cell-plate that represents the middle lamella between the walls of two adjacent cells.
  • At the time of cytoplasmic division, organelles like mitochondria and plastids get distributed between the two daughter cells.
  • In some organisms karyokinesis is not followed by cytokinesis as a result of which multinucleate condition arises leading to the formation of syncytium (e.g., liquid endosperm in coconut). (should be coenocytic)

Significance of mitosis

  • Mitosis results in the production of diploid daughter cells with identical genetic complement usually.
  • The growth of multicellular organisms is due to mitosis.
  • Cell growth results in disturbing the ratio between the nucleus and the cytoplasm. Therefore, cell divide to restore the nucleo-cytoplasmic ratio.
  • mitosis is important in cell repair. The cells of the upper layer of the epidermis, cells of the lining of the gut, and blood cells are being constantly replaced.
  • Mitotic divisions in the meristematic tissues – the apical and the lateral cambium, result in a continuous growth of plants throughout their life.

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Meiosis

  • The specialised kind of cell division that reduces the chromosome number by half results in the production of haploid daughter cells called
  • It is responsible for formation of haploid gametes, which during sexual reproduction form diploid zygote by fusion.
  • Meiosis involves two sequential cycles of nuclear and cell division called meiosis I and meiosis II but only a single cycle of DNA replication.
  • Interphase of meiosis is similar to interphase of mitosis.

 

Meiosis I

Prophase I

  • Prophase of the meiosis I division is typically longer and more complex than prophase of mitosis.
  • It has been further subdivided into the following five phases based on chromosomal behavior.

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 Metaphase I:

  • The bivalent chromosomes align on the equatorial plate.
  • The microtubules from the opposite poles of the spindle attach to the pair of homologous chromosomes.

Anaphase I:

  • The homologous chromosomes separate, while sister chromatids remain associated at their centromeres.

Telophase I

  • The nuclear membrane and nucleolus reappear.
  • cytokinesis follows telophase I.
  • Although in many cases the chromosomes do undergo some dispersion, they do not reach the extremely extended state of the interphase nucleus. The stage between the two meiotic divisions is called interkinesis and is generally short lived.
  • Interkinesis is followed by prophase II, a much simpler prophase than prophase I.

 

Meiosis II

Meiosis II resembles a normal mitosis.

Prophase II:

  • Meiosis II is initiated immediately after cytokinesis.
  • The nuclear membrane disappears by the end of prophase II.
  • The chromosomes again become compact.

Metaphase II:

  • At this stage the chromosomes align at the equator and the microtubules from opposite poles of the spindle get attached to the kinetochores of sister chromatids.

Anaphase II:

  • splitting of the centromere of each chromosome.
  • Chromosomes move toward opposite poles of the cell.

Telophase II:

  • the two groups of chromosomes once again get enclosed by a nuclear envelope.
  • cytokinesis follows resulting in the formation of four haploid daughter cells).

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SIGNIFICANCE OF MEIOSIS

  • by meiosis conservation of specific chromosome number of each species is achieved across generations in sexually reproducing organisms.
  • It also increases the genetic variability in the population of organisms from one generation to the next. Variations are very important for the process of evolution.

 

 

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CHAPTER 10 – CELL CYCLE AND CELL DIVISION

 

CHAPTER 9 – BIOMOLECULES

BIOMOLECULES

  • All living organisms are made up of similar elements
  • In living organisms Carbon and Hydrogen are in abundance with respect to other elements.           

            How to Analyse Chemical Composition?

  • To analyze the chemical composition, We can take any living tissue and grind it in trichloroacetic acid (Cl3CCOOH) using a mortar and a pestle. We obtain a thick slurry. If we were to strain this through a cheesecloth or cotton we would obtain two fractions
  1. filtrate or the acid-soluble pool,
  2. retentate or the acid-insoluble fraction.
  • Scientists have found thousands of organic compounds in the acid-soluble pool.
  • All the carbon compounds that we get from living tissues can be called ‘biomolecules’.

Living organisms have also got inorganic elements and compounds in them.

  • Wet weight – weight of living tissue/structure.
  • Dry Weight – weight of structure after drying it. (Wet weight – water).
  • Ash – ifthe tissue is fully burnt, all the carbon compounds are oxidised to gaseous form (CO2, water vapour) and are removed. What is remaining is called ‘ash’. This ash contains inorganic elements (like calcium, magnesium etc). (Dry weight – carbon compound)

Table : A Comparison of Elements Present in Non-living and Living Matter

Element % Weight of
Earth’s crust Human body
Hydrogen (H) 0.14 0.5
Carbon   (C) 0.03 18.5
Oxygen (O) 46.6 65.0
Nitrogen (N) very little 3.3
Sulphur (S) 0.03 0.3
Sodium (Na) 2.8 0.2
Calcium (Ca) 3.6 1.5
Magnesium (Mg) 2.1 0.1
Silicon (Si) 27.7 negligible

 

Table : A List of Representative Inorganic Constituents of Living Tissues

Component Formula
Sodium Na+
Potassium K+
Calcium Ca+2
Magnesium Mg+2
Water H2O
Compounds NaCl, CaCO3, PO4–3, SO4–2

Amino acids

  • Amino acids are organic compounds containing an amino group and an acidic group as substituents on the same carbon i.e., the α-carbon. Hence, they are called α-amino acids. They are substituted methanes.
  • There are four substituent groups occupying the four valency positions. These are hydrogen, carboxyl group, amino group and a variable group designated as R group.
  • Based on the nature of R group there are many amino acids. However, those which occur in proteins are only of twentyone types.
    • R group = hydrogen e.g., glycine
    • R group = methyl group e.g., alanine
    • R group = hydroxy methyl e.g., serine.

1

  • The chemical and physical properties of amino acids are essentially of the amino, carboxyl and the R functional groups.
    • Acidic amino acid – glutamic acid etc.
    • Basic amino acid – lysine
    • Neutral amino acid – valine.
    • aromatic amino acids – tyrosine, phenylalanine, tryptophan.
  • A particular property of amino acids is the ionizable nature of-NH2 and -COOH groups. Hence in solutions of different pHs, the structure of amino acids changes.

 

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Lipids

  • Lipids are generally water insoluble. They could be simple fatty acids.
  • A fatty acid has a carboxyl group attached to an R group. The R group could be a methyl (-CH3), or ethyl (-C2H5) or higher number of-CH2 groups (1 carbon to 19 carbons).
    • Palmitic acid has 16 carbons including carboxyl carbon.
    • Arachidonic acid has 20 carbon atoms including the carboxyl carbon.
  • Fatty acids could be saturated (without double bond) or unsaturated (with one or more C=C double bonds).
  • Another simple lipid is glycerol which is trihydroxy propane.
  • Many lipids have both glycerol and fatty acids. Here the fatty acids are found esterified with glycerol. They can be then monoglycerides, diglycerides and triglycerides.
  • These are also called fats and oils based on melting point. Oils have lower melting point (e.g., gingely oil) and hence remain as oil in winters.
  • Some lipids have phosphorous and a phosphorylated organic compound in them. These are phospholipids. They are found in cell membrane. Lecithin is one example.
  • Some tissues especially the neural tissues have lipids with more complex structures.

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Nucleotides

  • Many carbon compounds have heterocyclic rings like nitrogen bases -adenine, guanine, cytosine, uracil, and thymine.
  • When found attached to a sugar, they are called nucleosides.(nucleoside = sugar + nitrogen base). Adenosine, guanosine, thymidine, uridine and cytidine are nucleosides.
  • If a phosphate group is also found esterified to the sugar they are called nucleotides. (Nucleotides = nucleosides + phosphate). Adenylic acid, thymidylic acid, guanylic acid, uridylic acid and cytidylic acid are nucleotides.
  • Nucleic acids like DNA and RNA consist of nucleotides only. DNA and RNA function as genetic material.

1

 

 

 

Primary and Secondary Metabolites

  • Primary metabolites – Biomolecules which are present in all organisms and have identifiable functions and play known roles in normal physiologial processes.
  • Secondary metabolites – In plants, fungus and microbes many compounds other than primary metabolites are present. e.g,alkaloides, flavonoides, rubber, essential oils, antibiotics,coloured pigments, scents, gums, spices. The role or functions of all the secondary metabolitesare not known yet. many of them are useful to ‘human welfare’ (e.g., rubber, drugs, spices, scents and pigments). Some secondary metabolites have ecological importance.

 

Table : Some Secondary Metabolites
Pigments Carotenoids, Anthocyanins, etc.
Alkaloids Morphine, Codeine, etc.
Terpenoides Monoterpenes, Diterpenes etc.
Essential oils Lemon grass oil, etc.
Toxins Abrin, Ricin
Lectins Concanavalin A
Drugs Vinblastin, curcumin, etc.
Polymeric substances Rubber, gums, cellulose

BIOMACROMOLECULES

  • There is one feature common to all those compounds found in the acid soluble pool. They have molecular weights ranging from 18 to around 800 daltons (Da) approximately. (Micromolecules) (Mw= <1000 daltons)
  • The acid insoluble fraction, has only four types of organic compounds i.e., proteins, nucleic acids, polysaccharides and lipids. These classes of compounds with the exception of lipids, have molecular weights in the range of ten thousand daltons and above. (Macromolecules) (Mw= >1000 daltons)
  • The molecules in the insoluble fraction with the exception of lipids are polymeric substances.
  • Lipids are small molecular weightcompounds and are present not only as such but also arranged into structures like cell membrane and other membranes. When we grind a tissue, we are disrupting the cell structure. Cell membrane and other membranes are broken into pieces, and form vesicles which are not water soluble. Therefore, these membrane fragments in the form of vesicles get separated along with the acid insoluble pool and hence in the macromolecular fraction. Lipids are not strictly macromolecules.
  • The acid soluble pool represents roughly the cytoplasmic composition. The macromolecules from cytoplasm and organelles become the acid insoluble fraction. Together they represent the entire chemical composition of living tissues or organisms.

Table : Average Composition of Cells

Component % of the total cellular mass
Water 70-90
Proteins 10-15
Carbohydrates 3
Lipids 2
Nucleic acids 5-7
Ions 1

 

PROTEINS

  • Proteins are polypeptides. They are linear chains of amino acids linked by peptide bonds.
  • Each protein is a polymer of amino acids. As there are 21 types of amino acids (e.g., alanine, cysteine, proline, tryptophan, lysine, etc.), a protein is a heteropolymer and not a homopolymer.
  • A homopolymer has only one type of monomer repeating ‘n’ number of times.
  • Amino acids can be essential or non-essential. Essential amino acids are supplied in diet while our body prepares non essential amino acids.
  • Proteins carry out many functions in living organisms, some transport nutrients across cell membrane, some fight infectious organisms, some are hormones, some are enzymes,etc.
  • Collagen is the most abundant protein in animal world.
  • Ribulose bisphosphate Carboxylase-Oxygenase (RUBISCO) is the most abundant protein in the whole of the biosphere.

Table : Some Proteins and their Functions

Protein Functions
Collagen Intercellular ground substance
Trypsin Enzyme
Insulin Hormone
Antibody Fights infectious agents
Receptor Sensory reception (smell, taste, hormone, etc.)
GLUT-4 Enables glucose transport into cells

 

POLYSACCHARIDES

  • Polysaccharides are long chains of sugars. They are threads (literally a cotton thread) containing different monosaccharides as building blocks.

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  • Celluloseis a polymeric polysaccharide consisting of only one type of monosaccharide i.e., glucose. Cellulose is a homopolymer.
  • Starch is a variant of this but present as a store house of energy in plant tissues. Animals have another variant called glycogen.
  • Inulin is a polymer of fructose.
  • In a polysaccharide chain (say glycogen), the right end is called the reducing end and the left end is called the non-reducing end. It has branches.
  • Starch forms helical secondary structures. In fact, starch can hold I2 molecules in the helical portion. The starch-I2 is blue in colour. Cellulose does not contain complex helices and hence cannot hold I2.
  • Plant cell walls are made of cellulose. Paper made from plant pulp is cellulose. Cotton fibre is cellulose.
  • There are more complex polysaccharides in nature. They act as building blocks, amino-sugars and chemically modified sugars (e.g., glucosamine, N-acetyl galactosamine, etc.).
  • Exoskeletons of arthropods, for example, have a complex polysaccharide called chitin. These complex polysaccharides are heteropolymers.

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NUCLEIC ACIDS

  • Present in acid insoluble fraction of all living tissues.
  • These are polynucleotides. For nucleic acids, the building block is a nucleotide. A nucleotide has three chemically distinct components. One is a heterocyclic compound (N2 bases, the second is a monosaccharide and the third a phosphoric acid or phosphate.)
  • Adenine, Guanine, Uracil, Cytosine, and Thymine are N2 containing bases. Adenine and Guanine are substituted purines while the rest are substituted pyrimidines.
  • The sugar found in polynucleotides is either ribose (a monosaccharide pentose) or 2′ deoxyribose.
  • A nucleic acid containing deoxyribose is called deoxyribonucleic acid (DNA) while that which contains ribose is called ribonucleic acid (RNA).

STRUCTURE OF PROTEINS

  • Proteins are heteropolymers containing strings of amino acids. \
  • Biologists describe the protein structure at four levels.
    • Primary structure –

It is linear structure of protein.

the left end represented by the first amino acid and the right end represented by the last amino acid.

The first aminoacid is also called as N-terminal amino acid. The last amino acid is called the C-terminal amino acid.

Secondary structure –

The linear protein thread is folded in the form of a helix (similar to a revolving staircase).In proteins, only right handed helices are observed.

Tertiary structure –

The long protein chain is also folded upon itself like a hollow wollen ball, giving rise to the tertiary structure. This gives us a 3-dimensional view of a protein. Tertiary structure is absolutely necessary for the many biological activities of proteins.

Quaternary structure –

Some proteins are an assembly of more than one polypeptide or subunits. The manner in which these individual folded polypeptides or subunits are arranged with respect to each other (e.g. linear string of spheres, spheres arranged one upon each other in the form of a cube or plate etc.) is the architecture of a protein otherwise called the quaternary structure of a protein.

e.g., Adulthuman haemoglobin consists of 4 subunits. Two of these are identical to each other. Hence, two subunits of α type and two subunits of β type together constitute the human haemoglobin (Hb).

 

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NATURE OF BOND LINKING MONOMERS IN A POLYMER

  • In a polypeptide or a protein, amino acids are linked by a peptide bond which is formed when the carboxyl (-COOH) group of one amino acid reacts with the amino (-NH2) group of the next amino acid with the elimination of a water moiety (the process is called dehydration).
  • In a polysaccharide the individual monosaccharides are linked by a glycosidic bond. This bond is also formed by dehydration. This bond is formed between two carbon atoms of two adjacent monosaccharides.
  • In a nucleicacid a phosphate moiety links the 3′-carbon of one sugar of one nucleotide to the 5′-carbon of the sugar of the succeeding nucleotide. The bond between the phosphate and hydroxyl group of sugar is an ester As there is one such ester bond on either side, it is called phosphodiester bond.

Nucleic acids exhibit a wide variety of secondary structures.

one of the secondary structures exhibited by DNA is the famous Watson-Crick model.

Watson-Crick Model

  • According to this model DNA exists as a double helix. The two strands of polynucleotides are antiparallel i.e., run in the opposite direction.
  • The backbone is formed by the sugar-phosphate-sugar chain.
  • The nitrogen bases are projected more or less perpendicular to this backbone but face inside.
  • A and G of one strand compulsorily base pairswith T and C, respectively, on the other strand. There are two hydrogen bonds between A and T. There are three hydrogen bonds between G and C.
  • Each strand appears like a helical staircase.
  • Each step of ascent is represented by a pair of bases. At each step of ascent, the strand turns 36°.
  • One full turn of the helical strand would involve ten steps or ten base pairs.
  • On drawing a line diagram, the pitch would be 34Å. The rise per base pair would be 3.4Å. This form of DNA with the above mentioned salient features is called B-DNA.
  • There are more than a dozen forms of DNA named after English alphabets with unique structural features.

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DYNAMIC STATE OF BODY CONSTITUENTS – CONCEPT OF METABOLISM

  • living organisms contain thousands of organic compounds. These compounds or biomolecules are present in certain concentrations (expressed as mols/cell or mols/litre etc.).
  • allthese biomolecules have a turn over. This means that they are constantly being changed into some other biomolecules and also made from some other biomoleculesthrough chemical reactions. Together all these chemical reactions are called
  • These metabolic reactions result in the transformation of biomolecules like removal of CO2 from amino acids making an amino acid into an amine, removal of amino group in a nucleotide base; hydrolysis of a glycosidic bond in a disaccharide, etc.
  • Majority of these metabolic reactions are always linked to some other reactions or the metabolites are converted into each other in a series of linked reactions called metabolic pathways.
  • Flow of metabolites through metabolic pathway has a definite rate and direction. This metabolite flow is called the dynamic state of body constituents.
  • Another feature of these metabolic reactions is that every chemical reaction is a catalysed reaction. There is no uncatalysed metabolic conversion in living systems.
  • The catalysts which hasten the rate of a given metabolic conversation are also proteins. These proteins with catalytic power are named

METABOLIC BASIS FOR LIVING

  • Metabolic pathways can lead to a more complex structure from a simpler structure (for example, acetic acid becomes cholesterol) =anabolic pathways,or lead to a simpler structure from a complex structure (for example, glucose becomes lactic acid in our skeletal muscle)=catabolic pathways.
  • Anabolic pathways, as expected, consume energy. While, catabolic pathways lead to the release of energy, which is stored in the form of chemical bonds in ATP(adenosine triphosphate).

THE LIVING STATE

  • Many chemical compounds or metabolites, or biomolecules, are present at concentrations characteristic of each of them.

e.g., the blood concentration of glucose in a normal healthy individual is 4.5-5.0 mM, while that of hormones would be nanograms/ mL.

  • all living organisms exist in a steady-state characterised by concentrations of each of these biomolecules. These biomolecules are in a metabolic flux. Any chemical or physical process moves spontaneously to equilibrium.
  • The steady state is a non-equilibirium state. Because systems at equilibrium cannot perform work.
  • the living state is a non-equilibrium steady-state to be able to perform work; living process is a constant effort to prevent falling into equilibrium. This is achieved by energy input. Metabolism provides a mechanism for the production of energy. Hence the living state and metabolism are synonymous. Without metabolism there cannot be a living state.

 

ENZYMES

  • Almost all enzymes are proteins. There are some nucleic acids that behave like enzymes. These are called ribozymes.
  • An enzyme like any protein has a primary structure,secondary and the tertiary structure.
  • In tertiary structure, the backbone of the protein chain folds upon itself, the chain criss-crosses itself and hence, many crevices or pockets are made. One such pocket is the ‘active site’.
  • An active site of an enzyme is a crevice or pocket into which the substrate fits. Thus enzymes, through their active site, catalyse reactions at a high rate.
  • Enzyme catalysts differ from inorganic catalysts in many ways. Inorganic catalysts work efficiently at high temperatures and high pressures, while enzymes get damaged at high temperatures (above 40°C).

However, enzymes isolated from organisms who normally live under extremely high temperatures (e.g., hot vents and sulphur springs), are stable and retain their catalytic power even at high temperatures (upto 80°-90°C). Thermal stability is thus an important quality of such enzymes isolated from thermophilic organisms.

Chemical Reactions

  • Chemical compounds undergo two types of changes.

A physical change simply refers to a change in shape without breaking of bonds. This is a physical process. Another physical process is a change in state of matter: when ice melts into water, or when water becomes a vapour.

when bonds are broken and new bonds are formed during transformation, this will be called a chemical reaction. For example:

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hydrolysis of starch into glucose is an organic chemical reaction.

  • Rate of a physical or chemical process refers to the amount of product formed per unit time. It can be expressed as:

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Rate can also be called velocity if the direction is specified.

  • Rates of physical and chemical processes are influenced by temperature among other factors.
  • A general rule is that rate doubles or decreases by half for every 10°C change in either direction. Catalysed reactions proceed at rates vastly higher than that of uncatalysed ones. e.g.,

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In the absence of any enzyme this reaction is very slow, with about 200 molecules of H2CO3 being formed in an hour. However, by using the enzyme carbonic anhydrase, the reaction speeds about 600,000 molecules being formed every second.

  • A multistep chemical reaction, when each of the steps is catalysed by the same enzyme complex or different enzymes, is called a metabolic pathway. For example,

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This reaction is actually a metabolic pathway in which glucose becomes pyruvic acid through ten different enzyme catalysed metabolic reactions.

  • This pathway provides different products in different conditions –

In our skeletal muscle, under anaerobic conditions, lactic acid is formed.

Under normal aerobic conditions, pyruvic acid is formed.

In yeast, during fermentation, the same pathway leads to the production of ethanol (alcohol).

 How do Enzymes bring about such High Rates of Chemical Conversions?

  • Enzymes, i.e. proteins with three dimensional structures including an ‘active site’, convert a substrate (S) into a product (P). Symbolically, this can be depicted as:

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  • Substrate ‘S’ has to bind the enzyme at its ‘active site’ within a given cleft or pocket. The substrate has to diffusetowards the ‘active site’.
  • There is thus, an obligatory formation of an ‘ES’ complex. E stands for enzyme. This complex formation is a transient phenomenon.
  • During the state where substrate is bound to the enzyme active site, a new structure of the substrate called transition state structure is formed.
  • Very soon, after the expected bond breaking/making is completed, the product is released from the active site. In other words, the structure of substrate gets transformed into the structure of product(s).
  • There could be many more ‘altered structural states’ between the stable substrate and the product. all otherintermediate structural states are unstable. Stability is something related to energy status of the molecule or the structure.
  • If ‘P’ is at a lower level than’S’, the reaction is an exothermic reaction. One need not supply energy (by heating) in order to form the product.
  • However, whether it is an exothermic or spontaneous reaction or an endothermic or energy requiring reaction, the ‘S’ has to go through a much higher energy state or transition state.
  • The difference in average energy content of’S’ from that of this transition state is called ‘activation energy’.
  • Enzymes eventually bring down this energy barrier making the transition of’S’ to ‘P’ more easy.

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     Nature of Enzyme Action

  • Each enzyme (E) has a substrate (S) binding site in its molecule so that a highly reactive enzyme-substrate complex (ES) is produced. This complex is short-lived and dissociates into its product(s) P and the unchanged enzyme with an intermediate formation of the enzyme-product complex (EP).

The formation of the ES complex is essential for catalysis.

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  • The catalytic cycle of an enzyme action can be described in the following steps:
  1. First, the substrate binds to the active site of the enzyme, fitting into the active site.
  2. The binding of the substrate induces the enzyme to alter its shape, fitting more tightly around the substrate.
  3. The active site of the enzyme, now in close proximity of the substrate breaks the chemical bonds of the substrate and the new enzyme- product complex is formed.
  4. The enzyme releases the products of the reaction and the free enzyme is ready to bind to another molecule of the substrate and run through the catalytic cycle once again.

Factors Affecting Enzyme Activity

Factors affecting Enzyme activity are temperature, pH, change in substrate concentration or binding of specific chemicals that regulate its activity.

  1. Temperature and pH

Enzymes generally function in a narrow range of temperature and pH.

Each enzyme shows its highest activity at a particular temperature and pH called the optimum temperature and optimum pH.

Low temperature preserves the enzyme in a temporarily inactive state whereas high temperature destroys enzymatic activity because proteins are denatured by heat.

  1. Concentration of Substrate

With the increase in substrate concentration, the velocity of the enzymatic reaction rises at first. The reaction ultimately reaches a maximum velocity (Vmax) which is not exceeded by any further rise in concentration of the substrate. This is because the enzyme molecules are fewer than the substrate molecules and after saturation of these molecules, there are no free enzyme molecules to bind with the additional substrate molecules.

The activity of an enzyme is also sensitive to the presence of specific chemicals that bind to the enzyme. When the binding of the chemical shuts off enzyme activity, the process is called inhibition and the chemical is called an inhibitor.

Competitive inhibition –

When the inhibitor closely resembles the substrate in its molecular structure and inhibits the activity of the enzyme, it is known as competitive inhibitor. Due to its close structural similarity with the substrate, the inhibitor competes with the substrate for the substrate-binding site of the enzyme. Consequently, the substrate cannot bind and as a result, the enzyme action declines,

e.g., inhibition of succinic dehydrogenase by malonate which closely resembles the substrate succinate in structure.

Such competitive inhibitors are often used in the control of bacterial pathogens.

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Classification and Nomenclature of Enzymes

Enzymes are divided into 6 classes each with 4-13 subclasses and named accordingly by a four-digit number.

  1. Oxidoreductases/dehydrogenases: Enzymes which catalyse oxidoreduction between two substrates S and S’ e.g.,
  2. Transferases: Enzymes catalysing a transfer of a group, G (other than hydrogen) between a pair of substrate S and S’ e.g.,
  3. Hydrolases: Enzymes catalysing hydrolysis of ester, ether, peptide, glycosidic, C-C, C-halide or P-N bonds.
  4. Lyases: Enzymes that catalyse removal of groups from substrates by mechanisms other than hydrolysis leaving double bonds.
  5. Isomerases: Includes all enzymes catalysing inter-conversion of optical, geometric or positional isomers.
  6. Ligases: Enzymes catalysing the linking together of 2 compounds, e.g., enzymes which catalyse joining of C-O, C-S, C-N, P-O etc. bonds.

   Co-factors        

  • Enzymes are composed of one or several polypeptide chains. However, there are a number of cases in which non-protein constituents called co-factors are bound to the enzyme to make the enzyme catalytically active.
  • In these instances, the protein portion of the enzymes is called the apoenzyme.
  • Three kinds of cofactors may be identified: prosthetic groups, co-enzymes and metal ions.
  • Prosthetic groups are organic compounds and are distinguished from other cofactors in that they are tightly bound to the apoenzyme.

For example, in peroxidase and catalase, which catalyze the breakdown of hydrogen peroxide to water and oxygen, haem is the prosthetic group and it is a part of the active site of the enzyme.

  • Co-enzymes are also organic compounds but their association with the apoenzyme is only transient, usually occurring during the course of catalysis. Furthermore, co-enzymes serve as co-factors in a number of different enzyme catalyzed reactions. The essential chemical components of many coenzymes are vitamins, e.g., coenzyme nicotinamide adenine dinucleotide (NAD) and NADP contain the vitamin niacin.
  • Metal ions – A number of enzymes require metal ions for their activity which form coordination bonds with side chains at the active site and at the same time form one or more cordination bonds with the substrate, e.g., zinc is a cofactor for the proteolytic enzyme carboxypeptidase.

Catalytic activity is lost when the co-factor is removed from the enzyme which testifies that they play a crucial role in the catalytic activity of the enzyme.

 

 

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CHAPTER 9 – BIOMOLECULES

 

CH 8 – CELL: THE UNIT OF LIFE

CELL: THE UNIT OF LIFE

  • Cell   is —  Basic unit of life

—  Fundamental structural and functional unit of all living organisms.

  • Cytology – study of cell and cellular structures.
  • Types of organisms –

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  • All unicellular organisms are capable of
    • Independent existence.
    • Performing the essential functions of life.

Anything less than a complete structure of a cell does not ensure independent living. Hence, cell is the fundamental structural and functional unit of all living organisms.

  • Some important scientists –
Name of scientist Their work
Robert hooke Discovered cell
Anton von Leeuwenhoek first saw and described a live cell
Robert Brown Discovered nucleus
Schleiden (German botanist), Schwann (British Zoologist) Formulated Cell Theory
  • Robert hooke first time describe about cell in his book ‘Micrographia’. He actually saw cell wall of dead cells not cell itself.

 

  • CELL THEORY

    • Formulated by Schleiden and Schwann.
    • Modified by Rudolf Virchow – he explained that new cells develop from pre existing cells by cell division (Omnis cellula-e cellula).
    • Exception of cell theory – virus, viriods,
  1. All living organisms are composed of cells and products of cells.
  2. Cell is structural unit of life.
  • All cells arise from pre-existing cells.

 

  • CELL SIZE AND SHAPE

    • Smallest cell – mycoplasmas (PPLO – Pleuro Pneumonia Like Organisms)
    • Largest cell – egg of an ostrich.
    • Smallest cell in human body – Red Blood Cell.
    • Largest cell in human body – Ovum.
    • Longest cell in human body – Nerve Cell.

Even shape of cells may vary with the functions they perform.

 

  • TYPES OF CELL

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PROKARYOTIC CELL

  • Represented by Blue Green Algae, mycoplasmas, bacteria etc.

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  • Cell wall
    • Determine shape of cell.
    • Provide strong, structural support
    • Prevent bacteria from bursting or collapsing

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  • Plasma membrane
    • Semipermeable
    • Structurally similar to that of eukaryotes.
  • Mesosomes
    • Formed by extension of plasma membrane into cell.
    • In the form of vesicles, tubules and lamella.
    • Help in cell wall formation, DNA replication and distribution to daughter cells.
    • Also help in respiration, secretion processes, to increase the surface area of the plasma membrane and enzymatic content.
  • Chromatophores
    • Membranous extensions into cytoplasm.
    • Contain pigments.
    • In cyanobacteria.
  • Flagella
    • Present in motile cells.
    • Thin filamentous extensions from their cell wall.
    • Composed of three parts – filament, hook and basal body.
  • Pili and Fimbriae
    • Pili are elongated tubular structure while fimbriae are small bristle like fibres.
    • Help in attachment of bacteria.
  • Ribosomes
    • Associated with the plasma membrane of the cell.
    • Made of two subunits – 50S and 30S units which when present together form 70S.

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  • Site of protein synthesis.
  • Ribosome of a polysome translate the mRNA into protein.

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  • Inclusion bodies
    • For storage of reserve material in prokaryotic cells.
    • These are not bounded by any membrane system and lie free in the cytoplasm.
    • g., phosphate granules, cyanophycean granules and glycogen granules.
    • Gas vacuoles are found in blue green and purple and green photosynthetic bacteria.

 

EUKARYOTIC CELLS

  • Include all the protists, plants, animals and fungi.
  • Extensive compartmentalisation of cytoplasm through the presence of membrane bound organelles present.
  • possess an organised nucleus with a nuclear envelope.
  • genetic material is organised into chromosomes.

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  • Cell wall
    • non-living, rigid structure
    • forms an outer covering for the plasma membrane of fungi and plants.
    • gives shape to the cell and protects the cell from mechanical damage and infection.
    • it also helps in cell-to-cell interaction and provides barrier to undesirable macromolecules.

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  • Layers of cell wall
  1. Middle lamella
  • Outermost
  • Made up of mainly calcium pectate.
  • Holds or glues the different neighbouring cell together.
  1. Primary wall
    • Capable of growth.
    • Present in young cell.
    • Gradually diminishes as cell matures.
    • Madeup of cellulose, hemicelluloses.
    • Present in meristem, pith, cortex etc.
  2. Secondary wall
    • Innermost layer.
    • Lignified (in sclerenchyma, vesels, tracheids), suberinised (casparian strips, endodermis)
    • Suberin, lignin make cell wall impermeable.
    • Present in sclerenchyma, collenchyma, and vessels, tracheids.

 

  • Cell wall and middle lamella maybe traversed by plasmodesmata which connects the cytoplasm of neighbouring cells.

 

  • Cell membrane
    • Mainly composed of bilayer phospholipids, also possess protein and carbohydrate.
    • lipids are arranged within the membrane with the polar head (hydrophilic) towards the outer sides and the nonpolar tails (hydrophobic) towards the inner part.

This ensures that the nonpolar tail of saturated hydrocarbons is protected from the aqueous environment.

  • The ratio of protein and lipid varies in different cell types.

( In human RBC membrane has 52% protein and 40% lipids.)

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  • Structure of cell membrane is explained by Fluid Mosaic Model which was given by Singer and Nicolsan.
  • According to this model the quasi-fluid nature of lipid enables lateral movement of proteins within the overall bilayer.
  • The fluid nature of the membrane is important for functions like cell growth, formation of intercellular junctions, secretion, endocytosis, cell division etc.

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Fluid Mosaic Model

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  • Mitochondria
    • Double membrane bound cell organelle.

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  • Mitochondria are site of aerobic respiration. They produce ATP, hence called ‘Power House Of Cell’.
  • The matrix also possesses single circular DNA molecule, a few RNA molecules, ribosomes (70S) and the components required for the synthesis of proteins. So, mitochondria also known as ‘semi autonomous organelle’.
  • The mitochondria divide by fission and produce new mitochondria.

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  • Plastids
    • Found in all plant cells and in euglenoides.
    • They bear some specific pigments, thus imparting specific colours to the plants.

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  • Chloroplasts are mainly found in the mesophyll cells of the leaves.
  • These are various shaped like lens, oval, spherical, discoid, ribbon.
  • Double membrane bound Cell organelle. Inner is less permeable than outer.

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  • There are also stroma lamellae connecting the thylakoids of the different grana.
  • Stroma also contains small, double-stranded circular DNA molecules and ribosomes (70S). so, it is also known ‘semi autonomous organelle’.

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  • Endoplasmic Reticulum
    • a network or reticulum of tiny tubular structures scattered in the cytoplasm that is called the endoplasmic reticulum (ER)
    • Hence, ER divides the intracellular space into two distinct compartments, i.e., luminal(inside ER) and extra luminal(cytoplasm).

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  • Golgi apparatus
    • Discovered by Camillo Golgi.
    • They consist of many flat, disc-shaped sacs or cisternae stacked parallely.
    • The Golgi cisternae are concentrically arranged near the nucleus with distinct convex cis or the forming face and concave trans or the maturing face, which are interconnected.
    • The golgi apparatus principally performs the function of packaging materials.
    • golgi apparatus remains in close association with the endoplasmic reticulum as materials to be packaged in the form of vesicles from the ER fuse with the cis face of the golgi apparatus and move towards the maturing face.
    • A number of proteins synthesised by ribosomes on the endoplasmic reticulum are modified in the cisternae of the golgi apparatus before they are released from its trans
    • Golgi apparatus is the important site of formation of glycoproteins and glycolipids

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  • Lysosomes
    • These are membrane bound vesicular structures formed by the process of packaging in the golgi apparatus.
    • The isolated lysosomal vesicles have been found to be very rich in almost all types of hydrolytic enzymes (hydrolases – lipases, proteases, carbohydrases) optimally active at the acidic pH.
    • These enzymes are capable of digesting carbohydrates, proteins, lipids and nucleic acids.
  • Vacuoles
    • Membrane-bound space found in the cytoplasm. Membrane known as tonoplast.
    • It contains water, sap, excretory product and other materials not useful for the cell.
    • In plant cells the vacuoles are very large.
    • In plants, the tonoplast facilitates the transport of a number of ions and other materials against concentration gradients into the vacuole.
    • In Amoeba the contractile vacuole is important for excretion.
    • In many cells food vacuoles are formed by engulfing the food particles.

 

  • Ribosome
    • first observed under the electron microscope by George Palade.
    • They are composed of ribonucleic acid (RNA) and proteins.
    • Not Bounded by any membrane.
    • The eukaryotic ribosomes are 80S while the prokaryotic ribosomes are 70S.

(‘S’ stands for the sedimentation coefficient).

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  • Cytoskeleton
    • An elaborate network of filamentous proteinaceous structures present in the cytoplasm
    • Functions are mechanical support, motility, maintenance of the shape of the cell.
  • Cilia and Flagella
    • They are hair like outgrowths of cell membrane responsible for locomotion and movement of cell.
    • Cilia are small structures which work like oars, causing the movement of either the cell or the surrounding fluid. Flagella are comparatively longer.
    • Eukaryotic cilium and flagellum are covered with plasma membrane.
    • Their core called the axoneme, possesses a number of microtubules running parallel to the long axis. The axoneme usually has nine pairs of doublets of radially arranged peripheral microtubules, and a pair of centrally located microtubules. (9+2)
    • Both the cilium and flagellum emerge from centriole-like structure called the basal bodies.

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  • Centrosome and centriole
    • Centrosome is an organelle usually containing two perpendicularly lying centrioles surrounded by amorphous pericentriolar materials.
    • Centriole has an organisation like the cartwheel. They are made up of nine evenly spaced triplet peripheral fibrils of tubulin.
    • The central part of the centriole is also proteinaceous and called the hub, connected with peripheral tubules by radial
    • The centrioles form the basal body of cilia or flagella, and spindle fibres that give rise to spindle apparatus during cell division in animal cells.

 

  • Microbodies
    • Many membrane bound minute vesicles called microbodies that contain various enzymes.
    • They are present in both plant and animal cells.

 

  • Nucleus
    • first described by Robert Brown.
    • the material of the nucleus stained by the basic dyes was given the name chromatin by Flemming.
    • The interphase nucleus has nucleoprotein fibres called chromatin, nuclear matrix and one or more spherical bodies called
    • the nuclear envelope is consists of two parallel membranes with a space inbetween called perinuclear space.
    • The outer membrane usually remains continuous with the endoplasmic reticulum and also bears ribosomes on it.
    • At a number of places the nuclear envelope is interrupted by minute pores. These nuclear pores provide passages for movement of RNA and protein molecules.
    • Normally, there is only one nucleus per cell.Some mature cells even lack nucleus, e.g., erythrocytes of many mammals and sieve tube cells of vascular plants.
    • The nuclear matrix or the nucleoplasm contains nucleolus and chromatin.
    • The nucleoli are spherical structures present in the nucleoplasm. It is non-membrane bound. It is a site for active ribosomal RNA synthesis.
    • During cell division, chromatin network condenses into c
    • Chromatin contains DNA and some basic proteins called histones, some non-histone proteins and also RNA.
    • Every chromosome essentially has a primary constriction or the centromere on the sides of which disc shaped structures called kinetochores are present.

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  • Sometimes a few chromosomes have non-staining secondary constrictions at a constant location. This gives the appearance of a small fragment called the satellite.

 

 

PRINTABLE Pdf file of chapter notes are available…please click on the link…

CHAPTER 8 – CELL: THE UNIT OF LIFE