Biology · Chemistry

Biomolecules and Enzymes

1,432 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 statements is incorrect for SCOP?

  1. It stands for Structural Classification of Proteins.

  2. It is semi-automatic and hierachical classification of protein domains.

  3. It is a database which has manual classification of protein structural domains based on similarities of their amino acid sequences and three-dimensional structures.

  4. It utilises four levels of hierachical structural classification.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Statement B claims SCOP is 'semi-automatic and hierarchical' but SCOP is actually primarily manual with expert curation, not semi-automatic. Statement A is correct (Structural Classification of Proteins). Statement C is correct (manual classification based on sequence and structural similarities). Statement D is correct (four hierarchical levels: Class, Fold, Superfamily, Family). Thus B is the incorrect statement.

Multiple choice

Which of the following statements is incorrect for PDB?

  1. PDB archive contains information about experimentally determined structures of proteins, nucleic acids and complex assemblies.

  2. In this, users can perform simple and advanced searches based on annotations relating to sequence, structure and function.

  3. In this, the molecules can be visualised and analysed and can be downloaded.

  4. Data files contained in the PDB archive (ftp:// ftp.wwpodb.org) have copyright restrictions.
Reveal answer Fill a bubble to check yourself
D Correct answer
Multiple choice

Lysis of fibrin is brought about by

  1. plasmin

  2. hyaluronidase

  3. collagenase

  4. coagulase
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The plasmin proteins contain a euglobulin called plasminogen (or profibrinolysin) which when activated, becomes a substance called plasmin (or fibrinolysin). Plasmin is a proteolytic enzyme that resembles tryspin, the most important proteolytic digestive enzyme of pancreatic secretion.

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

Match group I (antimicrobial chemical agent) with group II (site of action.)

 
Group I Group II
A. Alcohol 1. Enzymes with dulfhydryl (SH) group
B. lodine 2. Cytoplasmic membrane
C. Acridine dyes 3. Peotein
D. Quaternary compounds 4. Nucleic acid

  1. (A) - 3 (B) - 1 (C) - 4 (D) - 2

  2. (A) - 1 (B) - 3 (C) - 2 (D) - 4

  3. (A) - 4 (B) -1 (C) - 3 (D) - 2

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

Alcohol disrupts the cytoplasmic membrane integrity (2), iodine oxidizes sulfhydryl groups in enzymes (1), acridine dyes intercalate into nucleic acids (4), and quaternary ammonium compounds denature proteins (3). The matching A-3, B-1, C-4, D-2 correctly pairs each agent with its primary site of action.

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

Which of the following pairs of amino acids will not be completely resolved by N – butanol : acetic acid : water (4 : 1 : 5)?

  1. Aspartic acid and glycine

  2. Histidine and gilycine

  3. Leucine and tyrorine

  4. Alanine and glycine
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In paper chromatography, compounds with identical Rf values in a given solvent system cannot be separated. Aspartic acid and glycine both have Rf=23 in the N-butanol-acetic acid-water (4:1:5) system, meaning they will migrate the same distance and remain unresolved.

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.