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 atoms is replaced by selenium in cysteine amino acid to form selenocysteine?

  1. Sulphur

  2. Nitrogen

  3. Oxygen

  4. Phosphorus

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

Selenocysteine is an L – α-amino acid found in a handful of proteins including certain peroxidases and reductases where it participates in the catalysis of electron transfer reactions. As its name implies, a selenium atom replaces the sulphur of its structural analog, cysteine.

Multiple choice

The imidazole group of amino acid A and the guanidino group of amino acid B exist as resonance hybrids with positive charge distributed between both nitrogens in form A or all three nitrogens in form B. Write the names of the amino acids A and B.

  1. A. Histidine, B. Asparagine

  2. A. Asparagine, B. Histidine

  3. A. Valine, B. Asparagine

  4. A. Valine, B. Alanine

  5. A. Leucine, B. Isoleucine
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Yes,  the given pair is Histidine and Asparagine. The imidazole group of histidine and the guanidino group of arginine exist as resonance hybrids with positive charge distributed between both nitrogens (histidine) or all three nitrogens (arginine).

Multiple choice

Which of the following statements is/are correct?

  1. Both L-amino acids and D-amino acids occur in nature.
  2. Only D-alpha-amino acids are present in proteins.
  3. All amino acids possess at least two weakly acidic functional groups, R-NH3+ and R-COOH.
  4. Amino acids do not possess any type of additional weakly acidic functional groups.

  1. None of these

  2. Only 1

  3. Only 3

  4. Only 2 and 4

  5. All of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

All amino acids possess at least two weakly acidic functional groups, R-NH3+ and R-COOH.

Multiple choice

Which of the following statements is/are correct?

  1. Amino acids are classified based on the properties of their R groups.
  2. Peptides are named for the number of amino acid residues present, and as derivatives of the carboxyl terminal residue.
  3. The partial double-bond character of the bond restricts the number of possible peptide conformations.

  1. Only I

  2. Only II

  3. Only III

  4. All of these

  5. None of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

All the statements are correct.

Multiple choice

Which is correct regarding partition chromatography?

  1. Association between each protein and the matrix is very strong.
  2. Proteins that interact more strongly with the stationary phase are retained longer.
  3. The time of protein association with the stationary phase depend only on mobile phases.

  1. Only 1

  2. Only 2

  3. Only 3

  4. 2 and 3

  5. 1 and 3
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Proteins that interact more strongly with the stationary phase are retained longer.

Multiple choice

Which of the following amino acids get replaced by valine amino acid in sickle cell anemia patients?

  1. Histidine

  2. Lysine

  3. Cysteine

  4. Glutamic acid

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

A single nucleotide pair alteration is the cause of sickle cell anemia: the template strand of mutated sickle cell DNA has an A rather than a T. U takes the place of A in the mRNA. A valine amino acid is made in the sickle cell haemoglobin instead of a glutamic acid. GAG which codes for the amino acid glutamic acid is changed to GTG for valine as a result of the mutation in the position of second nucleotide of the codon GAG.

Multiple choice

The sum total of all reactions occurring in the body, whether constructive or destructive is known as

  1. catabolism

  2. metabolism

  3. anabolism

  4. physiology
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Metabolism is the sum of all chemical reactions in an organism, including both anabolic (constructive, building complex molecules) and catabolic (destructive, breaking down molecules) pathways. Catabolism only refers to breakdown reactions, while anabolism refers only to building reactions. Physiology is the broader study of how organisms function.

Multiple choice

Peptide bond is formed between

  1. two amino groups

  2. carboxyl group and ketone group

  3. amino group and carboxyl group

  4. two carboxyl groups
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A peptide bond forms through a condensation reaction between the carboxyl group (-COOH) of one amino acid and the amino group (-NH2) of another amino acid, releasing a water molecule. This is the fundamental bond that links amino acids together in proteins.