MCQ 61:
Which of the following components is NOT part of a nucleotide?
A) Phosphate group
B) Sugar
C) Amino acid
D) Nitrogenous base
Answer: C) Amino acid
Explanation: A nucleotide consists of a phosphate group, a sugar (ribose in RNA, deoxyribose in DNA), and a nitrogenous base. Amino acids are the building blocks of proteins, not nucleotides.
MCQ 62:
Which of the following is a type of secondary structure found in proteins?
A) Disulfide bridge
B) Alpha-helix
C) Peptide bond
D) Glycosidic bond
Answer: B) Alpha-helix
Explanation: The alpha-helix is a common type of secondary structure in proteins, stabilized by hydrogen bonds. Disulfide bridges are part of tertiary structure, while peptide bonds link amino acids, and glycosidic bonds link carbohydrates.
MCQ 63:
Which of the following is an example of a polysaccharide?
A) Sucrose
B) Lactose
C) Starch
D) Fructose
Answer: C) Starch
Explanation: Starch is a polysaccharide composed of many glucose units and is used for energy storage in plants. Sucrose and lactose are disaccharides, while fructose is a monosaccharide.
MCQ 64:
What type of bond is primarily responsible for the stability of DNA’s double helix structure?
A) Ionic bonds
B) Hydrogen bonds
C) Covalent bonds
D) Peptide bonds
Answer: B) Hydrogen bonds
Explanation: Hydrogen bonds between complementary nitrogenous bases stabilize the double helix structure of DNA. Covalent bonds link the sugar and phosphate backbone, while ionic and peptide bonds are not involved in DNA structure.
MCQ 65:
Which of the following is an example of an essential amino acid?
A) Alanine
B) Glycine
C) Leucine
D) Serine
Answer: C) Leucine
Explanation: Leucine is an essential amino acid that must be obtained from the diet, while alanine, glycine, and serine can be synthesized by the body.
MCQ 66:
Which biomolecule serves as the genetic material in most organisms?
A) RNA
B) Proteins
C) DNA
D) Carbohydrates
Answer: C) DNA
Explanation: DNA (deoxyribonucleic acid) serves as the genetic material in most organisms, storing and transmitting genetic information. RNA plays a role in protein synthesis but is not the primary genetic material.
MCQ 67:
Which type of lipid is responsible for hormone production?
A) Triglycerides
B) Phospholipids
C) Steroids
D) Waxes
Answer: C) Steroids
Explanation: Steroids are a type of lipid involved in hormone production, including hormones like estrogen and testosterone. Triglycerides are for energy storage, phospholipids make up cell membranes, and waxes serve protective roles.
MCQ 68:
Which of the following enzymes breaks down carbohydrates?
A) Lipase
B) Protease
C) Amylase
D) Nuclease
Answer: C) Amylase
Explanation: Amylase is the enzyme responsible for breaking down carbohydrates, specifically starches into sugars. Lipase breaks down lipids, protease breaks down proteins, and nuclease breaks down nucleic acids.
MCQ 69:
What is the primary function of hemoglobin?
A) Energy storage
B) Oxygen transport
C) Immune response
D) Hormone regulation
Answer: B) Oxygen transport
Explanation: Hemoglobin is a protein in red blood cells that transports oxygen from the lungs to the tissues and returns carbon dioxide to the lungs. It does not store energy or regulate hormones.
MCQ 70:
Which of the following best describes a noncompetitive inhibitor?
A) Binds to the active site of an enzyme
B) Binds to a site other than the active site
C) Can be overcome by increasing substrate concentration
D) Permanently alters the enzyme
Answer: B) Binds to a site other than the active site
Explanation: A noncompetitive inhibitor binds to an enzyme at a site other than the active site, reducing enzyme activity regardless of substrate concentration. It does not permanently alter the enzyme and cannot be overcome by increasing substrate concentration.
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