Which one of the following statements is true?  from Life S

Subject

Life Sciences

Class

CNET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

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1.

Which one of the following statements is true? 

  • The specific rotation of enantiomers will be identical 

  • The rate constant of a first order reaction has only time but no concentration units

  • The value of pH + pOH depends on temperature 

  • The bond disassociation energy (kJ/mol) of –C–C– will be greater than –C ≡C– 


B.

The rate constant of a first order reaction has only time but no concentration units

Unit of rate constant for first order reaction (k) = min–1 or s–1 .The rate constant of a first order reaction has only time unit. It has no concentration unit. This means the numerical value of k for a first order reaction is independent of the unit in which concentration is expressed. If concentration unit is changed the numerical value of k for a first order reaction will not change. A reaction is said to be first order if its rate is determined by the change of one concentration term only. One can say that a first order reaction is one whose rate varies as 1st power of the concentration of the reactant i.e., the rate increases as number of times as the number of times the concentration of reactant is increased. 


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2.

Which one of the following statements on protein conformation is NOT true?

  • Dihedral angles of side-chains in amino acids are depicted in the Ramachandran plot

  • Infrared spectroscopy can be used to deduce hydrogen bonding in peptides

  • Three dimensional structures of protein composed of ~100 amino acids can be obtained by nuclear magnetic resonance spectroscopy

  • Globular proteins have α-helical and β-sheet components. 


3.

Choose the correct answer from the following statements on biosynthesis

  • In the biosynthesis of palmitate, all the carbon atoms are derived from activated malonate 

  • The amino acids Met, Thr, Lys, Ile, Val and Leu are biosynthesized from oxaloacetate and pyruvate in most bacteria 

  • Alanine is a major precursor for the biosynthesis of porphyrin

  • Tryptophan is converted to L-DOPA in the biosynthesis of epinephrine 


4.

Which one of the following statements on nucleic acids is NOT true? 

  • The conformation of ribose in DNA is α-2'-deoxy-D-ribofuranose

  • Hydrolysis of RNA takes place under alkaline conditions unlike DNA, as the 2'-hydroxyl in RNA acts as a nucleophile in an intramolecular displacement

  • DNA can occur in different three-dimensional forms 

  • In DNA, deamination of cytosine to uracil can occur in a non-enzymatic manner 


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5.

A rectangular photo frame of size 30cm× 40cm has a photograph mounted at the centre leaving a 5cm border all around. The area of the border is

  • 600 cm2

  • 350 cm2

  • 400 cm2

  • 700 cm2


6.

At birthday, every child gets 2 chocolates, every mother gets 1 chocolates, while no fathers gets a chocolate. In total 69 persons get 70 chocolates. If the number of children is half of the total number of mothers and fathers put together, then how many fathers are there?

  • 22

  • 23

  • 24

  • 69


7.

Following are statements on β-turns:

(a) all the 20 coded amino acids have equal propensity to form β-turns.

(b) Pro cannot occur in β-turns

(c)Pro-Gly sequence strongly favours β-turns.

(d) In Asn-Gly β-turns, Asn can have positive Φ, Ψ values.

  • (b), (d)

  • (a), (c)

  • (a), (d)

  • (c), (d)


8.

What is the significance of upwelling zone for marine ecosystems?

  • It is responsible for uniformity of temperature in ocean to support the marine life

  • It brings nutrients from deeper zones to relatively nutrient poor oceans surface thus increasing marine producity.

  • It is responsible for uniform oxygenation of marine waters thus increasing marine productivity

  • It helps in circulating decomposers from the bottom of ocean to surface for proper decomposition of dead material on the surface


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9.

Given below in column A are schematic representation of three types of pairwise species interaction and the name of some interaction are in column B

Select the best match for interaction between column A and B in each schematic figure.

  • A-(iii), B-(ii), C-(iv)

  • A-(iv), B-(ii), C-(iii)

  • A-(ii), B-(iv), C-(i)

  • A-(iii), B-(i), C-(ii)


10.

Consider a single locus with 2 alleles which are at Hardy-weinberg equilbrium. If the frequency of one the homozygous genotypes is 0.64, what is the frequency of heterzygotes in the population?

  • 0.16

  • 0.20

  • 0.32

  • 0.36


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