MCQ 81:
Which of the following is a characteristic of RNA?
A) Contains thymine
B) Double-stranded
C) Ribose sugar
D) Only found in the nucleus
Answer: C) Ribose sugar
Explanation: RNA contains ribose sugar and typically exists as a single-stranded molecule. It contains uracil instead of thymine and can be found in both the nucleus and cytoplasm.
MCQ 82:
What is the main function of enzymes in biochemical reactions?
A) To act as substrates
B) To increase the rate of reaction
C) To change the products formed
D) To require high temperatures
Answer: B) To increase the rate of reaction
Explanation: Enzymes are biological catalysts that increase the rate of biochemical reactions by lowering the activation energy required, without changing the products or needing high temperatures.
MCQ 83:
Which of the following is a property of lipids?
A) They are soluble in water.
B) They are hydrophobic.
C) They form polymers.
D) They contain nitrogen.
Answer: B) They are hydrophobic.
Explanation: Lipids are primarily hydrophobic and do not mix well with water. They do not form polymers like carbohydrates or proteins and may contain carbon, hydrogen, and sometimes oxygen but not nitrogen.
MCQ 84:
Which biomolecule is primarily responsible for energy storage in plants?
A) Glycogen
B) Starch
C) Cellulose
D) Chitin
Answer: B) Starch
Explanation: Starch is the main energy storage carbohydrate in plants, while glycogen is found in animals, cellulose provides structural support, and chitin is found in fungal cell walls and exoskeletons of arthropods.
MCQ 85:
Which amino acid is the starting point for protein synthesis in eukaryotic cells?
A) Methionine
B) Serine
C) Alanine
D) Cysteine
Answer: A) Methionine
Explanation: Methionine is the first amino acid incorporated during the synthesis of proteins in eukaryotic cells, due to its role as the initiator amino acid for translation.
MCQ 86:
Which of the following statements is true regarding competitive inhibitors?
A) They bind to the enzyme’s active site.
B) They can be overcome by increasing substrate concentration.
C) They permanently alter the enzyme’s structure.
D) Both A and B.
Answer: D) Both A and B.
Explanation: Competitive inhibitors bind to the active site of an enzyme, competing with the substrate. Their effects can be overcome by increasing substrate concentration, but they do not permanently alter the enzyme.
MCQ 87:
What is the primary function of cholesterol in the body?
A) Energy storage
B) Hormone synthesis
C) Structural component of cell membranes
D) All of the above
Answer: D) All of the above
Explanation: Cholesterol plays multiple roles in the body, including being a structural component of cell membranes, a precursor for hormone synthesis, and involved in energy storage.
MCQ 88:
Which of the following best describes the term “hydrophobic”?
A) Attracted to water
B) Repelled by water
C) Soluble in water
D) Contains polar bonds
Answer: B) Repelled by water
Explanation: Hydrophobic substances do not interact well with water and tend to be repelled by it. This characteristic is typical of many lipids.
MCQ 89:
Which type of RNA carries the genetic code from DNA to the ribosome?
A) rRNA
B) mRNA
C) tRNA
D) snRNA
Answer: B) mRNA
Explanation: Messenger RNA (mRNA) carries the genetic information from DNA to the ribosome for protein synthesis. Ribosomal RNA (rRNA) forms part of the ribosome, while transfer RNA (tRNA) brings amino acids to the ribosome.
MCQ 90:
Which of the following compounds is a result of the breakdown of fatty acids?
A) Acetyl CoA
B) Pyruvate
C) Glucose
D) Glycerol
Answer: A) Acetyl CoA
Explanation: The breakdown of fatty acids (beta-oxidation) produces acetyl CoA, which can enter the Krebs cycle. Pyruvate is produced from glucose, and glycerol is a component of triglycerides.
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