Biology · Chemistry

Biomolecules and Enzymes

1,501 Questions

This topic focuses on biomolecules, specifically proteins, enzymes, and amino acids. It includes questions on enzyme structures, protein folding, and catalysis. These concepts are crucial for medical and biology competitive exams.

Enzyme catalysisProtein structuresAmino acid synthesisPolypeptide chainsBiomolecule properties

Biomolecules and Enzymes Questions

Multiple choice

Which of the following is a pair of exclusively ketogenic amino acids?

  1. Leucine and Isoleucine

  2. Leucine and Lysine

  3. Lysine and Tyrosine

  4. Isoleucine and Lysine

  5. Leucine and Tyrosine
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A significant amount of metabolic energy can come from amino acid metabolism, particularly under conditions of starvation. Amino acids that are metabolized to produce acetyl-CoA and acetoacetate are called ketogenic amino acids. In humans, two amino acids are exclusively ketogenic: Leucine and Lysine.

Multiple choice

Match the following amino acids with their metabolic precursors and select the correct option.

 
Amino acid Metabolic precursor
A. Alanine 1. α-ketoglutarate
B. Glutamine 2. Pyruvate
C. Histidine 3. 3-phosphoglycerate
D. Serine 4. Ribose 5-phosphate

  1. A - 4, B - 3, C - 2, D - 1

  2. A - 2, B - 1, C - 3, D - 4

  3. A - 2, B - 1, C - 4, D - 3

  4. A - 3, B - 2, C - 4, D - 1

  5. A - 1, B - 2, C - 3, D - 4
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Alanine is most commonly produced by reductive amination of pyruvate. α-ketoglutarate (also known as oxoglutarate) is a precursor to glutamine. Ribose 5-phosphate is a key precursor to histidine. Glycerate 3-phosphate is a precursor to serine.

Multiple choice

Which of the following sets represents essential amino acids only?

  1. Tryptophan, Histidine, Aspartic acid, Proline, Leucine

  2. Valine, Leucine, Tryptophan, Lysine, Histidine

  3. Alanine, Proline, Aspartic acid, Glycine, Cysteine

  4. Valine, Leucine, Aspartic acid, Glycine, Cysteine

  5. Alanine, Valine, Lysine,Glycine, Tryptophan
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Valine, Leucine, Tryptophan, Lysine, Histidine: All are essential amino acids.

Multiple choice

Fungi are simple non-green plants that are not photosynthetic. Which of the following fungi draw their nutrients from the dead remains of plants and animals?

a. Mucor b. Puccinia c. Albugo d. Penicillium

  1. Only a and b

  2. Only b and d

  3. Only a and c

  4. Only a and d

  5. Only b and c
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

This is the correct option. Mucor and penicillium draw their nutrients from the dead remains of plants and animals. They are called decomposers.

Multiple choice

The presence of salt for preservation causes

  1. precipitation of enzyme protein

  2. reduction in sulphur linkage in enzyme protein

  3. reaction with aldehyde

  4. all of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Salt preservation works through multiple mechanisms, including precipitation of enzyme proteins. High salt concentration causes proteins to precipitate (salt-out effect), reducing enzymatic activity that leads to spoilage. This is one of the primary ways salt acts as a preservative in foods.

Multiple choice

Cholera toxin is a potentially harmful toxin produced by Vibrio cholera. It is made up of how many sub units?

  1. Three subunits (AB2 confirmation)

  2. Four subunits (AB3 confirmation)

  3. Five subunits (AB4 confirmation)

  4. Six subunits (AB5 confirmation)

  5. Seven subunits (AB6 confirmation)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Six subunits (AB5 confirmation). Cholera toxin acts on the intestinal walls of the GI tract and causes pores. As a result, mucous and other discharge comes out and is released with the feaces.

Multiple choice

Given below are the Rf values of some amino acids in two different solvents. The chromatography was carried out using whatman paper and the mode was ascending.

   
Amino acid Rf value N – butanol – acetic acid – water
(4 : 1 : 5) N – butanol– pyridine water
(1 : 1 : 1)
Aspartic acid 23 20
Alanine 30 37
Glycine 23 29
Histidine 1 24
Leucine 70 60
Lysine 12 13
Tyrosine 45 63

The mixture of amino acids can be separated satisfactorily by

  1. using N – butanol – acetic acid: water solvent system (4 : 1 : 5)

  2. using N – butanol – pyridine – water solvent system (1 : 1 : 1)

  3. by 2 – D chromatography using both the solvent system one at a time

  4. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Since some amino acids (like aspartic acid and glycine) co-migrate in one solvent but separate in another, two-dimensional chromatography is required. This technique uses two different solvent systems sequentially to achieve complete separation of all components.

Multiple choice

Non protein part of the enzyme is called

  1. holoenzyme

  2. apoenzyme

  3. coenzyme

  4. prosthetic group

  5. all the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Coenzymes are organic molecules that are required by certain enzymes to carry out catalysis.

Multiple choice

Inorganic part of the enzyme is called

  1. hormone

  2. coenzyme

  3. prosthetic group

  4. activator

  5. holoenzyme
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Enzyme activators are molecules that bind to enzymes and increase their activity. They are the opposite of enzyme inhibitors. It is the inorganic part of the enzyme.

Multiple choice

Which of the following is not a character of enzyme?

  1. They are specific in nature.

  2. They are used up in the reaction.

  3. They are proteinaceous in nature.

  4. They speed up the rate of reaction.

  5. The amino acids present in enzymes are linked together by peptide bonds.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

It is not used up in the reaction. At the end of the reaction, it remains unused.

Multiple choice

Which of the following is a pair of zinc-containing enzymes?

  1. Carboxypeptidase and ATPase

  2. Carbonic anhydrase and Phosphoglucomutase

  3. Carbonic anhydrase and Carboxypeptidase

  4. ATPase and Phosphoglucomutase

  5. Phosphoglucomutase and Carboxypeptidase
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Carboxypeptidase and Carbonic anhydrase are zinc-containing enzymes.

Multiple choice

Which of the following is a selenium-containing enzyme?

  1. Glutathione peroxidase

  2. Carbonic anhydrase

  3. Urease

  4. Dopamine beta-hydroxylase

  5. Tyrosinase
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Selenium is an important constituent of the enzyme glutathione peroxidase, which is responsible for destroying lipid-damaging peroxides.