Q71. Which of the following carbohydrates is a pentose sugar?
(a) Glucose
(b) Fructose
(c) Ribose
(d) Galactose
Answer: (c) Ribose
Explanation: Ribose is a pentose sugar (five-carbon sugar) found in RNA. Glucose, fructose, and galactose are hexose sugars (six-carbon sugars).
Q72. Which of the following is a reducing sugar?
(a) Sucrose
(b) Glucose
(c) Starch
(d) Cellulose
Answer: (b) Glucose
Explanation: Glucose is a reducing sugar, as it has a free aldehyde group that can donate electrons and reduce other substances. Sucrose is a non-reducing sugar because its glycosidic bond prevents it from having a free aldehyde or ketone group.
Q73. The main component of plant cell walls is:
(a) Glycogen
(b) Cellulose
(c) Chitin
(d) Starch
Answer: (b) Cellulose
Explanation: Cellulose is a polysaccharide that provides structural support to plant cell walls. It is composed of β-glucose units linked by β-1,4 glycosidic bonds.
Q74. The process of converting glucose into pyruvate in the cytoplasm is called:
(a) Glycolysis
(b) Gluconeogenesis
(c) Glycogenesis
(d) Glycogenolysis
Answer: (a) Glycolysis
Explanation: Glycolysis is the metabolic pathway that breaks down glucose into two molecules of pyruvate, producing ATP and NADH in the process. It occurs in the cytoplasm of cells.
Proteins MCQs (Continued)
Q75. Which level of protein structure involves α-helices and β-pleated sheets?
(a) Primary structure
(b) Secondary structure
(c) Tertiary structure
(d) Quaternary structure
Answer: (b) Secondary structure
Explanation: The secondary structure of a protein involves the folding of the polypeptide chain into α-helices and β-pleated sheets, which are stabilized by hydrogen bonds.
Q76. Which amino acid is commonly found at the active sites of enzymes because of its ability to form covalent bonds with substrates?
(a) Glycine
(b) Serine
(c) Proline
(d) Tyrosine
Answer: (b) Serine
Explanation: Serine is often found in the active sites of enzymes due to its reactive hydroxyl group (-OH), which can form covalent bonds with substrates during catalysis.
Q77. The three-dimensional shape of a protein is determined by its:
(a) Primary structure
(b) Secondary structure
(c) Tertiary structure
(d) Quaternary structure
Answer: (c) Tertiary structure
Explanation: The tertiary structure of a protein is its three-dimensional shape, formed by the interactions between the side chains (R-groups) of amino acids, including hydrophobic interactions, hydrogen bonds, ionic bonds, and disulfide bridges.
Q78. Hemoglobin consists of how many polypeptide chains?
(a) 1
(b) 2
(c) 3
(d) 4
Answer: (d) 4
Explanation: Hemoglobin is a tetramer consisting of four polypeptide chains—two alpha chains and two beta chains—that work together to carry oxygen in the blood.
Q79. Which of the following proteins has a fibrous structure?
(a) Hemoglobin
(b) Myoglobin
(c) Collagen
(d) Insulin
Answer: (c) Collagen
Explanation: Collagen is a fibrous protein that provides structural support to connective tissues such as skin, tendons, and ligaments. It is the most abundant protein in the human body.
Q80. Which vitamin is essential for blood clotting?
(a) Vitamin A
(b) Vitamin D
(c) Vitamin E
(d) Vitamin K
Answer: (d) Vitamin K
Explanation: Vitamin K plays a crucial role in the blood clotting process by helping in the synthesis of clotting factors, which are proteins involved in the formation of blood clots.
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