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

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

Phosphorus is a structural element in

  1. proteins

  2. cytochrome

  3. carbohydrates

  4. DNA

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

Phosphorus is a key structural component of DNA and RNA. DNA (deoxyribonucleic acid) is a nucleic acid, and its backbone contains phosphate groups which contain phosphorus. Proteins contain nitrogen but no phosphorus in their basic structure. Cytochrome is a protein, and carbohydrates contain carbon, hydrogen, and oxygen only.

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.

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.