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

Consider the following statements :

  1. The Penthose Phosphate Pathway supplies Erythrose-4-Phosphate which is the starting material in the synthesis of lignin.
  2. The Pentose Phosphate Pathway also occurs in plastids.
  3. NADPH is generated by the Pentose Phosphate Pathway. Which of the statements given above are correct?

  1. 1 and 2 only

  2. 2 and only

  3. 1 and 3 only

  4. 1,2 and 3
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Pentose Phosphate Pathway produces erythrose-4-phosphate which is precursor for aromatic amino acids and lignin synthesis. PPP operates in plastids (including chloroplasts). NADPH is generated as oxidative phase product. All three statements are correct.

Multiple choice

Below freezing point an enzyme is

  1. inactivated

  2. activated

  3. destroyed

  4. unaffected

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

Below freezing point, enzymes become inactivated (option A) because molecular motion virtually stops. They are not destroyed - enzyme activity returns when temperature rises above freezing. The 'activated' option incorrectly suggests cold enhances enzyme function.

Multiple choice

Which of the following enzymes helps in the production of urea?

  1. Uricase

  2. Urease

  3. Arginase

  4. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Arginase is the final enzyme in the urea cycle (ornithine cycle) that converts arginine to urea and ornithine in the liver. This is the fifth and final step of urea production. Urease breaks down urea (opposite direction), and uricase acts on uric acid, not urea production.

Multiple choice

Separation of amino acid into amino and carboxyl group is known as

  1. deamination

  2. excretion

  3. amination

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

Deamination is the process of removing an amino group (-NH2) from an amino acid. This is the first step in amino acid catabolism and is essential for producing energy from proteins or for converting amino acids into other compounds. The process occurs primarily in the liver and produces ammonia, which is then converted to urea for safe excretion.

Multiple choice

Primary structure of a protein is formed by

  1. hydrogen bonds

  2. disulphide bonds

  3. peptide bonds

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

The primary structure refers to amino acid linear sequence of the polypeptide chain. The primary structure is held together by covalent or peptide bonds.