MCQ Collection Pakistan MCQs Practice Pakistan questions with answers and explanations.
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A. The reactant acted upon by an enzyme B. The product only C. The enzyme's inhibitor D. A membrane lipid
Show Answer Correct Answer: A. The reactant acted upon by an enzyme
Explanation: Substrates bind to active sites.
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A. Activity always rises without limit B. Activity rises to an optimum and then may fall as the enzyme denatures C. Temperature has no effect D. Activity always falls with warming
Show Answer Correct Answer: B. Activity rises to an optimum and then may fall as the enzyme denatures
Explanation: Warming increases molecular collisions up to an optimum.
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A. All enzymes work best at pH 7 B. PH affects only carbohydrates C. Each enzyme has an optimal pH range D. PH never changes protein shape
Show Answer Correct Answer: C. Each enzyme has an optimal pH range
Explanation: PH alters ionization of amino-acid side chains.
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A. An inhibitor binds only to the product B. An inhibitor permanently removes the enzyme gene C. An inhibitor increases substrate concentration D. An inhibitor competes with substrate for the active site
Show Answer Correct Answer: D. An inhibitor competes with substrate for the active site
Explanation: Competitive inhibitors resemble or obstruct the substrate.
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A. An inhibitor binds away from the active site and changes enzyme activity B. An inhibitor occupies only the active site C. An inhibitor becomes the product D. An inhibitor increases enzyme synthesis
Show Answer Correct Answer: A. An inhibitor binds away from the active site and changes enzyme activity
Explanation: Noncompetitive binding changes enzyme shape or function.
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A. A storage polysaccharide B. The cell's main immediate energy-transfer molecule C. A membrane protein D. A DNA base
Show Answer Correct Answer: B. The cell's main immediate energy-transfer molecule
Explanation: ATP stores usable energy in phosphate bonds.
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A. Mitochondrial matrix B. Chloroplast stroma C. Cytoplasm D. Nucleus
Show Answer Correct Answer: C. Cytoplasm
Explanation: Glycolysis breaks glucose into pyruvate.
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A. To make DNA only B. To produce oxygen C. To synthesize cellulose only D. To transfer energy from organic molecules into ATP
Show Answer Correct Answer: D. To transfer energy from organic molecules into ATP
Explanation: Cellular respiration oxidizes fuel molecules.
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A. Mitochondrial matrix B. Cytoplasm C. Nucleus D. Golgi apparatus
Show Answer Correct Answer: A. Mitochondrial matrix
Explanation: The Krebs cycle oxidizes acetyl-CoA.
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A. To break glucose into carbon dioxide B. To convert light energy into chemical energy C. To produce ATP only for export D. To consume oxygen as the main reactant
Show Answer Correct Answer: B. To convert light energy into chemical energy
Explanation: Photosynthesis builds carbohydrates from carbon dioxide and water.
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A. A protein with phosphate groups only B. A glucose polymer C. A lipid with a hydrophilic head and hydrophobic tails D. A nucleic acid monomer
Show Answer Correct Answer: C. A lipid with a hydrophilic head and hydrophobic tails
Explanation: Phospholipids spontaneously form bilayers in water.
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A. Carbohydrates, lipids, proteins, and nucleic acids B. Vitamins, minerals, water, and salts C. Atoms, ions, tissues, and organs D. Sugars, acids, bases, and gases
Show Answer Correct Answer: A. Carbohydrates, lipids, proteins, and nucleic acids
Explanation: The four major macromolecule groups perform structural, energetic, catalytic, and informational roles.
