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 amino acid is synthesized from oxaloacetate through the aspartate aminotransferase reaction?

  1. Asparagine

  2. Glutamine

  3. Alanine

  4. Serine
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The aspartate aminotransferase reaction converts oxaloacetate to aspartate, using glutamate as a nitrogen source.

Multiple choice

What is the name of the enzyme that catalyzes the conversion of serine to glycine?

  1. Serine hydroxymethyltransferase

  2. Serine dehydratase

  3. Serine racemase

  4. Serine transaminase
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Serine hydroxymethyltransferase catalyzes the conversion of serine to glycine, with the release of a methylene group.

Multiple choice

Which amino acid is synthesized from pyruvate through the alanine aminotransferase reaction?

  1. Aspartate

  2. Glutamate

  3. Alanine

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

The alanine aminotransferase reaction converts pyruvate to alanine, using glutamate as a nitrogen source.

Multiple choice

What is the first step in the biosynthesis of the amino acid valine?

  1. Condensation of acetyl-CoA and propionyl-CoA

  2. Condensation of acetyl-CoA and butyryl-CoA

  3. Condensation of acetyl-CoA and isobutyryl-CoA

  4. Condensation of acetyl-CoA and valeryl-CoA
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The first step in the biosynthesis of valine is the condensation of acetyl-CoA and isobutyryl-CoA to form α-ketoisovalerate.

Multiple choice

Which amino acid is synthesized from phosphoenolpyruvate through the aspartate kinase reaction?

  1. Asparagine

  2. Glutamine

  3. Alanine

  4. Serine
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The aspartate kinase reaction converts phosphoenolpyruvate to aspartate, using ATP as an energy source.

Multiple choice

What is the name of the enzyme that catalyzes the conversion of threonine to glycine?

  1. Threonine deaminase

  2. Threonine aldolase

  3. Threonine racemase

  4. Threonine transaminase
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Threonine deaminase catalyzes the conversion of threonine to glycine, with the release of ammonia.

Multiple choice

Which amino acid is synthesized from α-ketoglutarate through the glutamate synthase reaction?

  1. Aspartate

  2. Glutamate

  3. Alanine

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

The glutamate synthase reaction converts α-ketoglutarate to glutamate, using ammonia and NADPH as cofactors.

Multiple choice

What is the first step in the biosynthesis of the amino acid leucine?

  1. Condensation of acetyl-CoA and propionyl-CoA

  2. Condensation of acetyl-CoA and butyryl-CoA

  3. Condensation of acetyl-CoA and isobutyryl-CoA

  4. Condensation of acetyl-CoA and valeryl-CoA
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The first step in the biosynthesis of leucine is the condensation of acetyl-CoA and butyryl-CoA to form α-ketoisocaproate.

Multiple choice

Which amino acid is synthesized from oxaloacetate through the malate dehydrogenase reaction?

  1. Asparagine

  2. Glutamine

  3. Alanine

  4. Serine
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The malate dehydrogenase reaction converts oxaloacetate to malate, using NADH as a cofactor.

Multiple choice

What is the name of the enzyme that catalyzes the conversion of methionine to cysteine?

  1. Methionine synthase

  2. Methionine adenosyltransferase

  3. Methionine racemase

  4. Methionine transaminase
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Methionine synthase catalyzes the conversion of methionine to cysteine, using vitamin B12 as a cofactor.

Multiple choice

Which amino acid is synthesized from α-ketobutyrate through the isoleucine aminotransferase reaction?

  1. Aspartate

  2. Glutamate

  3. Alanine

  4. Isoleucine
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The isoleucine aminotransferase reaction converts α-ketobutyrate to isoleucine, using glutamate as a nitrogen source.

Multiple choice

What is the first step in the biosynthesis of the amino acid lysine?

  1. Condensation of acetyl-CoA and propionyl-CoA

  2. Condensation of acetyl-CoA and butyryl-CoA

  3. Condensation of acetyl-CoA and isobutyryl-CoA

  4. Condensation of acetyl-CoA and valeryl-CoA
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The first step in the biosynthesis of lysine is the condensation of acetyl-CoA and propionyl-CoA to form α-ketoadipate.

Multiple choice

Which amino acid is synthesized from phosphoenolpyruvate through the pyruvate kinase reaction?

  1. Asparagine

  2. Glutamine

  3. Alanine

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

The pyruvate kinase reaction converts phosphoenolpyruvate to pyruvate, using ADP as an energy acceptor.

Multiple choice

Which of the following is NOT a common pathway for the breakdown of amino acids?

  1. Deamination

  2. Transamination

  3. Decarboxylation

  4. Phosphorylation
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Phosphorylation is not a common pathway for the breakdown of amino acids. Deamination, transamination, and decarboxylation are the three main pathways.

Multiple choice

What is the first step in the deamination of amino acids?

  1. Removal of the amino group

  2. Removal of the carboxyl group

  3. Removal of the side chain

  4. Removal of the hydrogen atom
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The first step in the deamination of amino acids is the removal of the amino group, which is catalyzed by enzymes such as aminotransferases and deaminases.