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 following amino acids is bitter in taste?

  1. Isoleucine

  2. Alanine

  3. Valine

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

Isoleucine is a branched-chain amino acid with a hydrophobic side chain, which gives it a bitter taste. The bitter taste in amino acids is associated with their nonpolar, aliphatic characteristics.

Multiple choice

Thioether group is present in which of following amino acids?

  1. Methionine

  2. Asparagine

  3. Lysine

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

Methionine contains a thioether group (-CH2-CH2-S-CH3) in its side chain, where a sulfur atom is bonded between two carbon atoms. This is a distinctive structural feature of methionine among the amino acids.

Multiple choice

Which of the following amino acids is coded by UAG?

  1. Methionine

  2. Lysine

  3. Pyrrolysine

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

UAG is typically a stop codon, but in certain archaea and bacteria, it codes for pyrrolysine, the 22nd proteinogenic amino acid. Pyrrolysine is used in methane-producing metabolism by some organisms.

Multiple choice

Which of the following is an essential amino acid?

  1. Tryptophan

  2. Isoleucine

  3. Phenylalanine

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Tryptophan, isoleucine, and phenylalanine are all essential amino acids that humans cannot synthesize and must obtain from their diet. Therefore, all of the listed options are correct.

Multiple choice

The pyrogenic streptococcal exotoxins SPE, A, B, and C ________________.

  1. are M proteins

  2. cause post-streptococcal autoimmune disease

  3. produce high titers of anti-streptolysin O

  4. are superantigens

  5. have hyaluronidase activity
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The superantigens combine with the framework regions of certain TCR V beta families irrespective of their complementarity determining regions.

Multiple choice

Among the following _________ is an amino acid.

  1. Atrazine

  2. Aspartic acid

  3. Azithromycin

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

Aspartic acid is an α-amino acid with the chemical formula HOOCCH(NH2)CH2COOH. The carboxylate anion, salt, or ester of aspartic acid is known as aspartate. The L-isomer of aspartate is one of the 20 proteinogenic amino acids, i.e., the building blocks of proteins. Its codons are GAU and GAC.

Multiple choice

____________ are examples of protein-protein interaction databases.

  1. BioGRID and Reactome

  2. STRING and SignaLink 2.0

  3. SignaLink 2.0 and Reactome

  4. BioGRID and STRING

  5. Reactome and STRING
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The Biological General Repository for Interaction Datasets (BioGRID) is a curated biological database of protein-protein and genetic interactions. STRING is a database of known and predicted protein interactions.

Multiple choice

Identify the incorrect matching.

  1. PROSITE: Database of protein families and domains

  2. Reactome: Navigable map of human biological pathways

  3. BRENDA: Comprehensive enzyme information system

  4. PhenomicDB: Database linking human mutations with phenotype

  5. PRINTS: A compendium of protein fingerprints
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

PhenomicDB is a multi-organism phenotype-genotype database including humans, mice, fruit flies, C.elegans and other model organisms.

Multiple choice

In the beta pleated-sheet, the R-groups of the amino acids

  1. generate H-bonds to stabilize the sheet

  2. are found above and below the plane of the sheet

  3. form only anti-parallel sheets

  4. lie in the plane of the sheet
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In beta pleated sheets, the polypeptide backbone lies in the plane of the sheet, with the peptide groups forming hydrogen bonds between adjacent strands. The R-groups (side chains) alternate above and below this plane, minimizing steric hindrance between adjacent side chains.