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 are incorrect?

  1. All transferrins are lipoproteins.
  2. The transport of iron from storage sites in cellular ferritin or hemosiderin occurs via serum-transport protein transferrin.
  3. Each transferrin binds with only one iron atom.
  4. The protein coat of ferritin is a hollow sphere of 24 polypeptide chains.

  1. 1 and 2

  2. 1 and 3

  3. 1 and 4

  4. 2 and 3

  5. 3 and 4
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This option is correct because all transferrins are glycoproteins and have a high molecular weight, they bind with two iron atoms.

Multiple choice

Which of the following is a pair of cell Fe storage proteins?

  1. Haemoglobin and myoglobin

  2. Transferrin and ferritin

  3. Ferritin and haemosiderin

  4. Haemosiderin and cytochrome c

  5. Cytochrome C and haemoglobin
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This option is correct because ferritin and haemosiderin are cell Fe storage proteins.

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 of the following are not common features of fimbriae and pili? P. Thin non-flagellar protein filaments found on the surface of bacteria. Q. Composed of the protein called pilin. R. Transfer genetic material during sexual reproduction of bacteria. S. Used for attachment to surfaces for colonization. Select the correct answer.

  1. P and Q

  2. P and R

  3. Q and R

  4. Q and S

  5. R and S
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Fimbriae are used for attachment to surfaces for colonization while pili are used to transfer genetic material during sexual reproduction of bacteria.

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.