MCQ 71:
Which of the following molecules are involved in the structure of ribosomes?
A) DNA
B) mRNA
C) rRNA
D) tRNA
Answer: C) rRNA
Explanation: Ribosomal RNA (rRNA) is a key component of ribosomes, where protein synthesis occurs. DNA carries genetic information, mRNA conveys that information to the ribosome, and tRNA brings amino acids.
MCQ 72:
Which of the following is a characteristic of enzymes?
A) They increase the energy of activation.
B) They are highly specific to their substrates.
C) They are consumed during the reaction.
D) They require heat for activity.
Answer: B) They are highly specific to their substrates.
Explanation: Enzymes are highly specific to their substrates, allowing them to catalyze particular reactions efficiently. They lower the activation energy, are not consumed in the reaction, and do not require excessive heat for activity.
MCQ 73:
Which of the following is an indicator of the presence of starch?
A) Biuret reagent
B) Benedict’s solution
C) Iodine solution
D) Sudan III
Answer: C) Iodine solution
Explanation: Iodine solution turns blue-black in the presence of starch. Biuret reagent tests for proteins, Benedict’s solution tests for reducing sugars, and Sudan III is a lipid stain.
MCQ 74:
Which of the following amino acids has a side chain that can be phosphorylated?
A) Serine
B) Valine
C) Phenylalanine
D) Glycine
Answer: A) Serine
Explanation: Serine contains a hydroxyl group in its side chain, allowing it to be phosphorylated, which is important for regulating protein activity. Valine, phenylalanine, and glycine do not have this capability.
MCQ 75:
Which of the following describes a saturated fatty acid?
A) Contains one or more double bonds
B) Solid at room temperature
C) Liquid at room temperature
D) Derived only from plant sources
Answer: B) Solid at room temperature
Explanation: Saturated fatty acids have no double bonds between carbon atoms, which makes them solid at room temperature. Unsaturated fatty acids contain one or more double bonds and are usually liquid at room temperature.
MCQ 76:
Which of the following processes converts pyruvate into lactate?
A) Oxidative phosphorylation
B) Fermentation
C) Krebs cycle
D) Glycolysis
Answer: B) Fermentation
Explanation: Fermentation is the process that converts pyruvate into lactate (in muscles) or ethanol (in yeast) under anaerobic conditions. Glycolysis breaks down glucose into pyruvate, while the Krebs cycle and oxidative phosphorylation occur in aerobic respiration.
MCQ 77:
Which vitamin is primarily involved in the synthesis of coenzyme A?
A) Vitamin B1
B) Vitamin B5
C) Vitamin B2
D) Vitamin B12
Answer: B) Vitamin B5
Explanation: Vitamin B5 (pantothenic acid) is a precursor to coenzyme A, which is essential for fatty acid metabolism and the Krebs cycle. The other B vitamins have different roles in metabolism.
MCQ 78:
Which of the following structures represents the tertiary structure of proteins?
A) Linear chain of amino acids
B) Alpha-helix and beta-sheet
C) Three-dimensional folding
D) Dimeric arrangement
Answer: C) Three-dimensional folding
Explanation: The tertiary structure of proteins refers to their three-dimensional folding, which results from interactions among side chains. The linear chain is primary structure, and alpha-helices and beta-sheets are secondary structures.
MCQ 79:
Which of the following statements about enzymes is true?
A) They are made of nucleic acids.
B) They can be denatured by extreme temperatures.
C) They are only active at high pH levels.
D) They change the equilibrium constant of a reaction.
Answer: B) They can be denatured by extreme temperatures.
Explanation: Enzymes are primarily proteins, and they can be denatured by extreme temperatures and pH levels, which can affect their function. They do not change the equilibrium constant of reactions and can function in a range of pH levels.
MCQ 80:
Which of the following is a function of carbohydrates?
A) Energy source
B) Structural support
C) Cell recognition
D) All of the above
Answer: D) All of the above
Explanation: Carbohydrates serve multiple functions, including acting as an energy source, providing structural support (like cellulose in plants), and facilitating cell recognition through glycoproteins and glycolipids.
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