Free Enzymes MCQs with Answers
633 Enzymes MCQs from Biology, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Enzymes are biological catalysts that lower activation energy without being consumed, and their specificity is explained by the lock and key and induced fit models. Work includes the effects of temperature, pH and substrate concentration on reaction rate, plus competitive and non-competitive inhibition and how these differ.
Last updated
Read the Enzymes notesFree MDCAT chapter notes with key terms633 questions · page 14 of 32
- A. Coenzyme
- B. Apoenzyme
- C. Holoenzyme
- D. Proenzyme
Explanation: OPTION A: The co-enzymes are the derivatives of vitamins. e.g. ATP, NAD+, and FAD+ are common coenzymes.OPTION B: The protein part of the…
Correct answer: Holoenzyme- A. Never changes
- B. Forms no chemical bond with substrate
- C. Is non-specific in its action
- D. Determined by structure and the specificity of the enzyme
Explanation: Enzymes are proteins, and their function is determined by their complex structure.The reaction takes place in a small part of the enzyme…
Correct answer: Determined by structure and the specificity of the enzyme- A. No Linkage with enzyme
- B. Strong linkage with enzyme
- C. Medium linkage
- D. Weak linkage with enzyme
Explanation: Inhibitors inhibit the activity of enzymes by reducing the rate of their reactions.
Correct answer: Weak linkage with enzyme- A. 6.8
- B. 6
- C. 8.8
- D. 8
Explanation: Salivary amylase, an enzyme in the saliva that breaks down starch has an optimal pH of 6.7 - 7.0. Hence, A is the correct option.
Correct answer: 6.8- A. Substrates must bind the enzyme's active site in order to initiate its effects
- B. Enzymes increase both the forward and reverse rate of a reaction
- C. Enzymes are not destroyed in a reaction and can be used in the same reaction countless times
- D. Enzymes increase the amount of product created in a reaction
Explanation: OPTION A: The catalytic activity of an enzyme is located in its active site.
Correct answer: Enzymes increase the amount of product created in a reaction- A. Coenzyme
- B. Apoenzyme
- C. Holoenzyme
- D. Proenzyme
Explanation: Option A : If the non-protein part of the enzyme is loosely attached to the protein part of the enzyme, it is known as a coenzyme.
Correct answer: Apoenzyme- A. Concentration of enzyme
- B. Concentration of substrate
- C. Concentration of enzyme-substrate complex
- D. Concentration of inhibitor
Explanation: Option A :The extent of inhibition in non-competitive inhibition does not depend on the concentration of the enzyme.
Correct answer: Concentration of inhibitor- A. Low temperature
- B. Nature of substrate
- C. Maximum pH level
- D. Amount of enzyme present at a specific time at unlimited substrate concentration
Explanation: Option A : At low temperatures, enzymes are inactive.Option B:The nature of the substrate does not affect the rate.
Correct answer: Amount of enzyme present at a specific time at unlimited substrate concentration- A. The Keq of a reaction remains unchanged in the presence of an enzyme
- B. Enzymes speed up the rate of reaction in DNA synthesis
- C. Harsh, acidic conditions can completely denature an enzyme
- D. An enzyme is completely converted to product during metabolism.
Explanation: Option A: Kéq of reaction remains unchanged in the presence of an enzyme. This is true about enzymes.
Correct answer: An enzyme is completely converted to product during metabolism.- A. Malonic acid
- B. Malic acid
- C. Succinic acid
- D. Palmitic acid
Explanation: A substrate of succinic dehydrogenase is fumaric acid. This is when succinic is converted into fumarate in the krebs cycle.
Correct answer: Succinic acid- A. Increases
- B. Decreases
- C. No affect
- D. Increases or decreases depending upon individual enzyme
Explanation: b) Decreases:Option (b) "Decreases" is the correct answer. Enzymes significantly decrease the activation energy of a reaction.
Correct answer: Decreases- A. Vitamin C
- B. Vitamin B
- C. Vitamin B1
- D. Vitamin B2
Explanation: Vitamin C is the only vitamin that does not act as a coenzyme. Coenzymes are non-protein compounds that are necessary for the functioning…
Correct answer: Vitamin C- A. Prosthetic group
- B. Coenzyme
- C. Holoenzyme
- D. Activator
Explanation: Based on the options you provided, the correct answer is "coenzyme." A detachable cofactor is referred to as a coenzyme.
Correct answer: Coenzyme- A. Ligase
- B. Hydrolase
- C. Isomerase
- D. Pyrimidine complex
Explanation: Pyrimidine is one of two classes of heterocyclic nitrogenous bases found in nucleic acids; DNA and RNA.
Correct answer: Pyrimidine complex- A. Shape of substrate
- B. Shape of inhibitor
- C. Shape of enzyme
- D. None of these
Explanation: In mixed inhibition, the inhibitor binds to an allosteric site, i.e. a site different from the active site where the substrate binds.This…
Correct answer: Shape of enzyme- A. The primary structure of enzymes
- B. The secondary structure of enzymes
- C. Tertiary structure of enzymes
- D. Quaternary structure of enzymes
Explanation: The specificity of the substrate of the protein structure is determined by the tertiary structure.
Correct answer: Tertiary structure of enzymes- A. Prosthetic group
- B. Coenzyme
- C. Activator
- D. Cofactor
Explanation: C is correct option because activator are inorganic cofactors which can be easily deattached from enzymes.These are only attached to…
Correct answer: Activator- A. Ionic
- B. Hydrogen
- C. Disulphide
- D. All of these
Explanation: D is correct option because usually a polypeptide chains bends and folds upon itself forming a globular shape This is the protein tertiary…
Correct answer: All of these- A. DNA polymerase
- B. Adenylate cyclase
- C. Phosphoprotein phosphatase
- D. Nitric oxide synthetase
Explanation: The correct answer is Phosphoprotein phosphatase because this enzyme is directly regulated by calcium ions, which play a critical role in…
Correct answer: Phosphoprotein phosphatase- A. Change in pH of the surroundings
- B. Change in the charge of the active site
- C. Change in temperature
- D. Formation of the enzyme-substrate complex
Explanation: Formation of Enzyme Substrate complex is the step that causes activation of the catalytic site of an enzyme.
Correct answer: Formation of the enzyme-substrate complex