GATE Life Sciences 2009 PPT1

8/4/2019 GATE Life Sciences 2009 PPT1

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GATE LIFE SCIENCES 2009GATE LIFE SCIENCES 2009GATE LIFE SCIENCES 2009GATE LIFE SCIENCES 2009

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Q.1 Which of these can be an antigen but cannot induce

immune responses?

(A) Hemocyanin(B) Influenza virus(C) Azobenzene arsonate(D) Corynebacteria

Ans C

P-Azobenzenearsonate is a hapten which capable of eliciting bothantibody formation and delayed hypersensitivity when bound toaromatic amino acids, polypeptides or proteins. Haptens can elicit an

immune response only when attached to a large carrier.


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Q.2 Generally, the rate-limiting step of major metabolic pathways isa reaction

(A) in which the availability of the substrate is limited.(B) catalyzed by an allosteric enzyme.(C) catalyzed by an enzyme with very low Km.(D) whose products are not readily consumed by the subsequent step ofthe pathway.

Ans C

The rate-limiting step of every metabolic pathway is far from equilibriumbecause of the relatively low activity of the enzyme that catalyzes it. Therate of this reaction is not limited by substrate availability, but only by

the activity of this enzyme. Low Km of enzyme indicates a high affinitybetween enzyme and substrate, meaning that the rate will approach Vmaxmore quickly.


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Q.3 Equal volumes of two buffers of pH 4 and pH 6 of identical ionic

strengths are mixed. The resultant pH is

(A) close to 4.(B) close to 5.(C) close to 6.(D) exactly 5.

Ans A

The hydrogen ion concentration ([H+] concentration (mol/l)) in asolution of pH 4 is 0.0001 (1 x 10-4 ). Similarly the hydrogen ionconcentration in a solution of pH 6 is 0.000001( 1x10-6). When you add

two solutions of identical ionic strengths (you get a mixture of all ions inthe solution), the sum is equal to (0.0001 + 0.000001 = 0.000101).0.000101 is closer to 0.0001 and hence the pH is closer to 4.


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Q.4 The formation of ATP from ADP and Pi is not a spontaneous reaction.A reason for this is

(A) ATP readily ionizes.(B) electrostatic repulsion in ATP is lower than that in ADP.(C) ATP is better hydrated than the total hydration levels of ADP and Pi.(D) resonance stabilization of P-O bonds in Pi is higher than that in ATP.

ATP is an unstable molecule in and gets hydrolysed to ADP and phosphateeasily. This is because the strength of the bonds between the phosphate

groups in ATP are less than the strength of the hydrogen bonds(hydration bonds), between its products (ADP + phosphate), and water.

Ans D


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Q.5 A beam of light passes through 1 cm of a colored solution. Eightypercent of the incident light is transmitted. If the incident light passesthrough 2 cm of the same solution, the percentage of transmitted light is

(A) 60(B) 64(C) 70

(D) 40

Ans A

According to the Law of absorption the amount of light absorbed isproportional to the thickness of the absorbing material and is independent

of the intensity of the incident light.


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Q.6 Kyoto Protocol is related to

(A) Acid rain(B) Photochemical smog(C) Ozone hole(D) Global warming

Ans D

Kyoto Protocol sets binding targets for 37 industrializedcountries and the European community for reducing greenhousegas (GHG) emissions which in turn lead to global warming.


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Q.7During receptor-mediated endocytosis of LDL bound to itsreceptor

(A) both receptor and ligand are degraded,(B) the receptor is degraded and the ligand is recycled.(C) both are recycled.(D) the ligand is degraded and the receptor is recycled.

Ans D

The receptor is recycled and returned to the plasma membrane to collectmore LDL particles where as the ligand or LDL is broken down tocholesterol, amino acids and fatty acids.


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Q.8Which of the following statements are INCORRECT ?

P. The frequency of recombination is a measure of linkage between geneson the same chromosome.Q. DNA polymerase I is the true DNA replicase in E.coli.R. The conserved element closest to the transcription initiation site iscalled the CAAT box.S. The introns in the nuclear pre-mRNAs are excised by spliceosomes.

(A) P. Q(B) Q. R(C) P. R(D) P. S

Ans B


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Q.9

(A) P-1, Q-5, R-6, S-3 (B) P-2, Q-6, R-3, S-4 (C) P-1, Q-6, R-4, S-2 (D) P-1, Q-2, R-6, S-4

Ans B


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Q.10 Density of cells of a bacterial culture is routinely measured using

Spectrophotometer. This is based on the principle of

(A) Light absorption(B) Light diffraction(C) Light scattering(D) Light reflection

Ans A

A spectrophotometer is used to measure the amount of light a sample (beit liquid or solid) absorbs.


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Q.11 Pseudopeptidoglycan is present in the cell wall of

(A) Escherichia coli

(B) Bacillus subtilis(C) Saccharomyces cerevisiae(D) Methanococcus jannaschii

Ans D

Pseudopeptidoglycan is a major cell wall component of some archaea.The basic components of Pseudopeptidoglycan are N-acetylglucosamineand N-acetyltalosaminuronic acid (Peptidoglycan has N-acetylmuramicacid instead), which are linked by a -1,3-glycosidic bond.


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Q.12 A silent mutation is one that

(A) results in a truncated polypeptide(B) replaces an amino acid with an equivalent amino acid in a polypeptide(C) does not change the amino acid sequence of the polypeptide(D) changes the reading frame of the mRNA leading to an alteredpolypeptide

Ans C

Silent mutations are DNA mutations that do not result in achange to the amino acid sequence of a protein. They may occur ina non-coding region (outside of a gene or within an intron), or they

may occur within an exon in a manner that does not alter the finalamino acid sequence.


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Q.13 RecA is a protein involved in

(A) Recombinational repair(B) Mismatch repair(C) Nucleotide excision repair(D) Base excision repair

Ans A

RecA is a protein in E. coli involved in recombinational repair ofdamaged DNA and in SOS repair. RecA catalyzes strand pairing, orstrand assimilation-the joining of two different DNAs by

homologous base pairing with each other.


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Q.14 Effective chemotherapeutic agents are difficult to develop forthe treatment of fungal infections because

(A) Fungi have cell wall.(B) Fungi have better mechanisms to inactivate drugs.(C) Fungi are eukaryotic cells and their cellular machinery is similar tothat of the host.(D) Fungal pathogens typically infect organs inaccessible for antibiotic

treatment.

Ans A

Fungi are eukaryotic and are composed of rigid cell wall largely made of

chitin which is a polymer of N-acetylglucosamine rather thanpeptidoglycan which is a characteristic component of most bacterial cellwalls.


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Q.15 During hibernation in a hibernating mammal, its body

temperature would be(A) Lower than normal state(B) Same as normal state(C) Higher than normal state(D) Fluctuate between high and low points

Ans A

Hibernation is a state of inactivity and metabolic depression in animals,

characterized by lower body temperature, slower breathing, and lowermetabolic rate.


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Q.16 Mendels principle of segregation means that the germ cells(egg or sperm) always receive

(A) One of the paired alleles(B) One pair of alleles(C) One quarter of the genes(D) Any pair of alleles

Ans A

The Law of Segregation states that every individual possesses a pair ofgenes for any particular trait and that each parent passes a randomlyselected copy of only one of these to its offspring through eggs orsperms.


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Q.17 Anabolic steroids, taken illegally by sportspersons to enhancetheir physical strength, are synthetic analogues for natural

_______________ from the ___________.

(A) testosterone .....,. anterior pituitary(B) FSH and LH ....... posterior pituitary(C] cortisol ..,....... thyroid(D) androgen ......... gonads

Ans A

They are drugs which mimic the effects of the male sex hormones:testosterone and dihydrotestosterone. They increase protein synthesis

within cells, which results in the buildup of cellular tissue (anabolism),especially in muscles.


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Q.18 Homology in anatomical parts helps in determining evolutionarykinship because

(A) Homologous body parts invariably perform similar functions(B] Display evolutionary adaptations(C] Undergo similar genetic changes(D) Have common embryological origin

Ans D

Homologous structures are similar in different species because thespecies have common descent. They may or may not perform the samefunction. An example is the forelimb structure shared by cats andwhales.


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Q.19 The human immune system is able to mount a response when itencounters a novel microorganism for the first time because

(A) White blood cells are able to change their antigen specificitydepending upon the microorganism they interact with.(B) Our body contains millions of different kinds of white blood cells,each with a unique type of antigen receptor.(C) Bone marrow cells make different antigen receptors depending uponthe kind of invading microorgamsrn.

(D) Bone marrow cells are able to change their antigen specificity uponphysical interaction with the microorganism.

Ans C

The clonal selection hypothesis states that the germline encodes manydifferent antigen receptors - one for each antigenic determinant towhich an individual will be capable of mounting an immune response.


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Q.20 To produce plants that are homozygous for all traits, the bestchoice is

(A) Protoplatst culture(B) Cell suspension culture(C) Anther and pollen culture(D) Apical meristem culture

Ans C

Anther and pollen culture helps to produce haploid plants containing asingle set of chromosomes. Haploid plants can be used to producehomozygous diploid or polyploid plants which are valuable for

breeding.


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GATE Life Sciences 2009 PPT1