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

Directions: Read the given statements and choose the correct option.

Assertion: Non-competitive inhibitors do not compete with the substrate for the enzyme’s active site. Reason: Sulfanilamide is an example of non-competitive inhibitors.

  1. A and R are both correct and R is the correct explanation of A.

  2. A and R are both correct and R is not the correct explanation of A.

  3. A is correct and R is incorrect.

  4. A is incorrect and R is correct.

  5. A and R are both incorrect.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This option is correct because non-competitive inhibitors do not compete with the substrate for the enzyme’s active site. Instead, they interact with another part of the enzyme and sulfanilamide is an example of competitive inhibitors.

Multiple choice

Which one of the following amino acids in proteins does NOT undergo phosphorylation?

  1. Ser

  2. Thr

  3. Pro

  4. Tyr
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Proline (Pro) is the only common amino acid in proteins that does not undergo phosphorylation. Phosphorylation occurs on hydroxyl-containing amino acids: serine (Ser, A), threonine (Thr, B), and tyrosine (Tyr, D). These hydroxyl groups serve as nucleophilic targets for kinases. Proline has a secondary amine as its side chain (it's an imino acid that forms a cyclic structure with the backbone), lacking any hydroxyl group that could be phosphorylated. This unique structure also makes proline a helix breaker in protein secondary structure.

Multiple choice

Which of the following statements is/are false?

a. An enzyme like any protein has a primary structure. b. There are some ribosomes that behave like enzymes and they are called ribozymes. c. Catabolic pathways lead to the release of energy.

  1. Only a

  2. Only a and b

  3. Only b

  4. Only b and c

  5. Only c
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This is a correct option as the statement 'a' and 'b' both false. An enzyme like any protein has the secondary and the tertiary structure.There are some nucleic acids that behave like enzymes and they are called ribozymes.

Multiple choice

Match the following:

 
a. Prosthetic groups 1. They form coordination bonds with side chains at the active site and also form one or more coordination bonds with the substrate.
b. Co-enzymes 2. They are organic compounds, but their association with the apoenzyme usually occurs during the course of catalysis.
c. Metal ions 3. They are organic compounds that are tightly bound to the apoenzyme.

  1. a - 3, b - 2, c - 1

  2. a - 3, b - 1, c - 2

  3. a - 1, b - 3, c - 2

  4. a - 2, b - 3, c - 1

  5. a - 1, b - 2, c - 3
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This is the correct option. Prosthetic groups are organic compounds that are tightly bound to the apoenzyme. Co-enzymes are organic compounds, but their association with the apoenzyme usually occurs during the course of catalysis. Metal ions form coordination bonds with side chains at the active site and also form one or more coordination bonds with the substrate.

Multiple choice

Deamination occurs in liver to

  1. get rid of ammonia from blood

  2. synthesise amino acids

  3. make use of excess amino acids

  4. convert proteins to urea and uric acid

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Deamination in the liver removes amino groups (-NH2) from amino acids, producing toxic ammonia. The liver then converts ammonia to urea via the urea cycle for safe excretion. This process prevents ammonia accumulation while allowing nitrogen waste removal. It's not about synthesizing amino acids or making direct use of excess amino acids.

Multiple choice

Which of the following features are associated with cysteine amino acid?

  1. A. Aliphatic, B. 2 methyl groups and C. Sulphur atom

  2. A. Aliphatic, B. 3 methyl groups and C. Carboxylic acid functional group

  3. A. Aliphatic, B. 2 methyl groups and C. Hydroxyl functional group

  4. A. Aromatic, B. 2 methyl groups and C. Hydroxyl functional group

  5. A. Aliphatic, B. 5 methyl groups and C. No functional group
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

These features are of cysteine amino acid.