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 plays the crucial role in the tertiary structure of the protein?

  1. Disulfide bonds

  2. Fatty acids

  3. Esters

  4. Hemiacetals

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

A disulfide bond (Br.E. disulphide bond) is a covalent bond, usually derived by the coupling of two thiol groups. The linkage is also called an SS-bond or disulfide bridge. The overall connectivity is therefore R–S–S–R. The terminology is widely used in biochemistry.

Multiple choice

Which is the only glycosaminoglycan that is exclusively nonsulfated?

Glycosaminoglycans have high degrees of heterogeneity with regards to molecular weight, disaccharide construction and sulfation due to the fact that GAG synthesis, unlike proteins or nucleic acids, is not template driven, and dynamically modulated by processing enzymes. Members of the glycosaminoglycan family vary in the type of hexosamine, hexose or hexuronic acid unit they contain.

  1. Hyaluronan

  2. Heparin

  3. Keratan sulfate

  4. Heparan sulfate

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

Hyaluronan (also called hyaluronic acid or hyaluronate or HA) is an anionic, nonsulfated glycosaminoglycan distributed widely throughout  connective, epithelial and neural tissue.

Multiple choice

Which of the following proteoglycans are included in the small leucine - rich proteoglycan family?

Small leucine-rich proteoglycan (SLRP) family consists of a protein core containing leucine repeats with a glycosaminoglycan (GAG) chain consisting of either chondroitin sulfate (CS) or dermatansulfate (DS).

  1. Versican

  2. Decorin

  3. Aggrecan

  4. Perlecan

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

Decorin is a proteoglycan that is on average 90 - 140 kilodalton (kD) in molecular weight, included in the small leucine-rich proteoglycan family.

Multiple choice

Which of the following is not correct about proteins?

  1. It is known to form tissues in the body.

  2. Nitrogen is its main constituent.

  3. It can be directly stored in the body.

  4. It can release energy when the body is in its need.

  5. It gets converted into urea and excretes out of the body with urine.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The protein is not stored in the body. Hence, this statement is incorrect.

Multiple choice

Collagen, $\alpha$-keratin and tropomyosin have common structural features. They are (P) disulfide bridges to neighboring proteins. (Q) repeating sequences of amino acids (R) a high 3-sheet content (S) superhelical coiling

  1. P, Q

  2. Q, R

  3. Q, S

  4. P, R
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Collagen, alpha-keratin, and tropomyosin are all fibrous structural proteins characterized by repeating amino acid sequences and a coiled-coil or superhelical structural motif. They do not share high beta-sheet content, as collagen is a triple helix of polyproline II-like helices and keratin and tropomyosin are primarily alpha-helical.

Multiple choice

Which of the following amino acid change (mutation) would MOST adversely affect the structure of an $\alpha$-helix?

  1. A valine residue changed to an isoleucine residue

  2. A methionine residue changed to a proline residue

  3. An aspartic acid residue changed to a glutamic acid residue

  4. A histidine residue changed to an arganine residue
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Proline is an alpha-helix breaker because its rigid cyclic side chain lacks the hydrogen atom needed to participate in backbone hydrogen bonding and introduces a steric kink into the peptide chain.

Multiple choice

The protein responsible for spongy structure in bread is

  1. Albumin

  2. Zein

  3. Gluten

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

Gluten, composed of gliadin and glutenin proteins, forms a viscoelastic network in bread dough that traps carbon dioxide produced by yeast, resulting in the characteristic spongy structure of baked bread.

Multiple choice

Which one of the following statements is NOT TRUE in terms of nutritive evaluation of proteins?

  1. PER is defined as the live weight gain per unit weight of protein intake.

  2. ‘Metabolic nitrogen’ is the amount of nitrogen present in the feces when a nitrogen free diet is fed to an animal.

  3. Net protein utilization is a product of biological value and digestibility.

  4. ‘Chemical score’ of a mixed protein diet can be calculated from the total amino acids present in the mixture.
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice

What is NOT one of the common chromophores in the body

  1. collagen

  2. pigment

  3. lymph

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

Common chromophores in the body include melanin (pigment), hemoglobin (blood), water, and collagen. Lymph is not a primary chromophore that absorbs laser light in the same way.