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Biomolecules (Biology) · Question 70

AIPMT 2010 (Mains)MCQEasy📈 Topic in 38% papers+4−1
1

Three of the following statements about enzymes are correct and one is wrong. Which one is wrong?

  1. Enzymes require optimum pH for maximal activity.
  2. Enzymes are denatured at high temperature but in certain exceptional organisms they are effective even at temperatures 80 –90 .
  3. Enzymes are highly specific.
  4. Most enzymes are proteins but some are lipids.

Answer

(4) Most enzymes are proteins but some are lipids.

Solution

As per NCERT, almost all enzymes are proteins; there are some nucleic acids (RNA) that behave like enzymes – ribozymes. No enzyme is a lipid.

⇒ Statement (4) is wrong.

∵ Each enzyme shows its highest activity at an optimum pH and temperature; enzymes of organisms living in hot vents and sulphur springs remain active even at 80 –90 ; and enzymes are highly specific for their substrates,

∴ statements (1), (2) and (3) are correct.

Answer: (4)

AIPMT 2010 (Mains)

Keep practising — Biomolecules (Biology)

2

The figure given below shows the conversion of a substrate into product by an enzyme. In which one of the four options (1 – 4) the components of reaction labelled as A, B, C and D are identified correctly? [figure]

  1. array|l|l|l|l| A & B & C & D \ Potential energy & Transition state & Activation energy & Activation energy without enzyme \ array
  2. array|l|l|l|l| A & B & C & D \ Transition state & Potential energy & Activation energy without enzyme & Activation energy with enzyme \ array
  3. array|l|l|l|l| A & B & C & D \ Potential energy & Transition state & Activation energy with enzyme & Activation energy without enzyme \ array
  4. array|l|l|l|l| A & B & C & D \ Activation energy with enzyme & Transition state & Activation energy without enzyme & Potential energy \ array
AIPMT 2010 (Mains)
3

Carbohydrates are commonly found as starch in plant storage organs. Which of the following five properties of starch (A – E) make it useful as a storage material? The useful properties are

  1. (A), (C) and (E)
  2. (A) and (E)
  3. (B) and (C)
  4. (B) and (D)
AIPMT 2008
4

A competitive inhibitor of succinic dehydrogenase is

  1. -ketoglutarate
  2. malate
  3. malonate
  4. oxaloacetate
AIPMT 2008
5

About 98 percent of the mass of every living organism is composed of just six elements including carbon, hydrogen, nitrogen, oxygen and

  1. sulphur and magnesium
  2. magnesium and sodium
  3. calcium and phosphorus
  4. phosphorus and sulphur
AIPMT 2007
6

An organic substance bound to an enzyme and essential for its activity is called

  1. isoenzyme
  2. coenzyme
  3. holoenzyme
  4. apoenzyme
AIPMT 2006
7

The catalytic efficiency of two different enzymes can be compared by the

  1. formation of the product
  2. pH of optimum value
  3. Km value
  4. molecular size of the enzyme.
AIPMT 2005
8

Which one of the following statements regarding enzyme inhibition is correct?

  1. Competitive inhibition is seen when a substrate competes with an enzyme for binding to an inhibitor protein.
  2. Competitive inhibition is seen when the substrate and the inhibitor compete for the active site on the enzyme.
  3. Non-competitive inhibition of an enzyme can be overcome by adding large amount of substrate.
  4. Non-competitive inhibitors often bind to the enzyme irreversibly.
AIPMT 2005
9

Enzymes, vitamins and hormones can be classified into a single category of biological chemicals, because all of these

  1. help in regulating metabolism
  2. are exclusively synthesized in the body of a living organism as at present
  3. are conjugated proteins
  4. enhance oxidative metabolism.
AIPMT 2005
10

Which of the following is the simplest amino acid?

  1. Alanine
  2. Asparagine
  3. Glycine
  4. Tyrosine
AIPMT 2005
11

Nucleotides are building blocks of nucleic acids. Each nucleotide is a composite molecule formed by

  1. base-sugar-phosphate
  2. base-sugar-OH
  3. (base-sugar-phosphate)n
  4. sugar-phosphate
AIPMT 2005

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