Cyanide is poisonous because it irreversibly inhibits ____.
Correct answer C. cytochrome oxidase in the respiratory chain
Subject / 1,067 questions
MDCAT Biology MCQs
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- Biological Molecules 74
- Coordination and Control 72
- Biology Diagnostic 70
- Cell Structure and Function 67
- Biotechnology 65
- Reproduction 58
- Bioenergetics 55
- Circulation 50
- Inheritance 48
- Digestion 45
- Immunity 45
- Support and Movement 45
- Acellular Life (Viruses) 45
- Homeostasis 45
- Respiration and Gaseous Exchange 45
- Evolution 45
- Enzymes 45
- Cell Cycle 41
- Chromosome and DNA 40
- Biology Introduction 38
- Ecosystem 27
Organophosphate nerve gases and some insecticides are toxic because they inhibit ____.
Correct answer A. acetylcholinesterase
An inhibitor that forms strong covalent bonds with an enzyme and permanently inactivates it is called ____.
Correct answer D. an irreversible inhibitor
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In feedback inhibition, the end product of a metabolic pathway ____.
Correct answer A. inhibits an enzyme early in the pathway
A site on an enzyme, separate from the active site, where regulatory molecules bind is the ____.
Correct answer C. allosteric site
The protein part of an enzyme that is inactive without its cofactor is called the ____.
Correct answer B. apoenzyme
An organic cofactor that is tightly and permanently bound to its enzyme is a ____.
Correct answer D. prosthetic group
Which one of these cofactors is classed as a coenzyme?
Correct answer B. NAD⁺
Many coenzymes are derived from ____.
Correct answer A. water-soluble vitamins
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Metal ions such as Zn²⁺ in carbonic anhydrase act as ____.
Correct answer A. activators (inorganic cofactors)
Digestive enzymes such as lipase and amylase that break bonds by adding water belong to which class?
Correct answer C. Hydrolases
Chemically, most enzymes are ____.
Correct answer D. globular proteins
How does an enzyme speed up a chemical reaction?
Correct answer A. By lowering the activation energy of the reaction
Which feature of a reaction is NOT altered by an enzyme?
Correct answer D. The overall free energy change between reactants and products
Why are enzymes needed only in small amounts?
Correct answer D. They are not used up and can be reused many times
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The region of an enzyme to which the substrate binds and where catalysis occurs is the ____.
Correct answer D. active site
The temporary association formed when a substrate binds to an enzyme is called the ____.
Correct answer A. enzyme-substrate complex
The lock and key model of enzyme action was proposed by ____.
Correct answer D. Emil Fischer
According to the induced fit model, the active site ____.
Correct answer B. changes shape slightly to mould around the substrate
Daniel Koshland’s contribution to the study of enzymes was ____.
Correct answer A. the induced fit model of enzyme action