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 true regarding transamination?

P. Transamination means transfer of amide nitrogen from a donor molecule to an acceptor molecule. Q. Liver is the main site for transamination. R. Transamination reactions are irreversible. S. Transamination reactions are catalysed by aminotransferases.

  1. P and Q

  2. P and R

  3. P and S

  4. Q and R

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

This option is correct because liver is the main site for transamination and transamination reactions are catalysed by aminotransferases (transaminases).

Multiple choice

For the identification of which of the following entities is Sanger’s reagent?

  1. N-terminal of a peptide chain

  2. C-terminal of a peptide chain

  3. Side chain of amino acid

  4. Molecular weight of the peptide chain

  5. Number of amino acids in the peptide chain
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This option is correct because Sanger’s reagent is use for determining the N-terminal amino acid in peptide chains, in particular insulin.

Multiple choice

Which of the following is a pair of exclusively ketogenic amino acids?

  1. Leucine and Isoleucine

  2. Leucine and Lysine

  3. Lysine and Tyrosine

  4. Isoleucine and Lysine

  5. Leucine and Tyrosine
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A significant amount of metabolic energy can come from amino acid metabolism, particularly under conditions of starvation. Amino acids that are metabolized to produce acetyl-CoA and acetoacetate are called ketogenic amino acids. In humans, two amino acids are exclusively ketogenic: Leucine and Lysine.

Multiple choice

Match the following amino acids with their metabolic precursors and select the correct option.

 
Amino acid Metabolic precursor
A. Alanine 1. α-ketoglutarate
B. Glutamine 2. Pyruvate
C. Histidine 3. 3-phosphoglycerate
D. Serine 4. Ribose 5-phosphate

  1. A - 4, B - 3, C - 2, D - 1

  2. A - 2, B - 1, C - 3, D - 4

  3. A - 2, B - 1, C - 4, D - 3

  4. A - 3, B - 2, C - 4, D - 1

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

Alanine is most commonly produced by reductive amination of pyruvate. α-ketoglutarate (also known as oxoglutarate) is a precursor to glutamine. Ribose 5-phosphate is a key precursor to histidine. Glycerate 3-phosphate is a precursor to serine.

Multiple choice

Which of the following sets represents essential amino acids only?

  1. Tryptophan, Histidine, Aspartic acid, Proline, Leucine

  2. Valine, Leucine, Tryptophan, Lysine, Histidine

  3. Alanine, Proline, Aspartic acid, Glycine, Cysteine

  4. Valine, Leucine, Aspartic acid, Glycine, Cysteine

  5. Alanine, Valine, Lysine,Glycine, Tryptophan
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Valine, Leucine, Tryptophan, Lysine, Histidine: All are essential amino acids.

Multiple choice

The presence of salt for preservation causes

  1. precipitation of enzyme protein

  2. reduction in sulphur linkage in enzyme protein

  3. reaction with aldehyde

  4. all of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Salt preservation works through multiple mechanisms, including precipitation of enzyme proteins. High salt concentration causes proteins to precipitate (salt-out effect), reducing enzymatic activity that leads to spoilage. This is one of the primary ways salt acts as a preservative in foods.

Multiple choice

For prediction of three-dimensional structure of protein, P. homology modeling tries many possible alignments Q. threading first identifies homologues R. threading evaluates many rough models S. homology modelling optimises one model

  1. Q, S

  2. P, Q

  3. R, S

  4. Q, R
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The statement asks which statements are correct. P (homology modeling tries many possible alignments) is TRUE because homology modeling must test different alignments between the target and template to find the best structural fit. Q (threading first identifies homologues) is also TRUE because threading methods search structural databases to find potential homologous templates before threading the sequence. R is false (threading doesn't evaluate many rough models - it selects templates). S is false (homology modeling doesn't just optimize one model - it explores multiple alignments).