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.
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- A. 30°C
- B. 40°C
- C. 50°C
- D. 20°C
Explanation: Most enzymes have an optimum temperature at which they function most efficiently.
Correct answer: 40°C- A. Activators
- B. Prosthetic groups
- C. Coenzymes
- D. Apoenzymes
Explanation: A coenzyme is a non-protein organic compound that binds with an enzyme to catalyze a reaction.
Correct answer: Coenzymes- A. Competitive inhibitor
- B. Non-competitive inhibitor
- C. Reversible inhibitor
- D. Irreversible inhibitor
Explanation: A non-competitive inhibitor is a type of enzyme inhibitor that binds to an enzyme at a location other than the active site.
Correct answer: Non-competitive inhibitor- A. Fasten
- B. Inhibit
- C. Reverse
- D. Decrease
Explanation: If another molecule, having a shape very similar to the enzyme's substrate, binds to its active site, it would then inhibit the enzyme's…
Correct answer: Inhibit- A. Glucose
- B. Fumarate
- C. Succinic acid
- D. Malonate
Explanation: Malonate has structural similarity with succinic acid and it binds competitively with the active site of succinic acid dehydrogenase…
Correct answer: Malonate- A. Decrease activation energy
- B. Increase activation energy
- C. Inorganic catalyst
- D. None of the above.
Explanation: The correct answer is: decrease activation energy. Enzymes are proteins that act as biological catalysts, facilitating chemical reactions…
Correct answer: Decrease activation energy- A. Optimum pH
- B. Optimum temperature
- C. Enzyme concentration
- D. Substrate concentration
Explanation: Enzymes exhibit their highest activity at a specific pH level, referred to as the optimum pH.
Correct answer: Optimum pH- A. Metallic ions
- B. Organic molecules
- C. Inorganic molecules
- D. Radicals
Explanation: Cofactors are substances that help enzymes function properly. Inorganic cofactors act as activators, while organic cofactors can be either…
Correct answer: Organic molecules- A. 1
- B. 2
- C. 3
- D. 4
Explanation: Allosteric enzymes have, in addition to their active site for substrate binding, another site called the allosteric site.
Correct answer: 2- A. Activator
- B. Coenzyme
- C. Prosthetic group
- D. Apo-enzyme
Explanation: The detachable cofactor is known as an activator if it is an inorganic ion.
Correct answer: Prosthetic group331. Three of the following statements about enzymes are correct and one is wrong. Which one is wrong?
- A. Enzymes require optimum pH for maximal activity
- B. Enzymes are denatured at high temperatures but in certain exceptional organisms, they are effective even at temperatures 80° - 90°C
- C. Enzymes are highly specific
- D. Most enzymes are proteins, but some are lipids
Explanation: This statement is incorrect. Enzymes are primarily proteins. While there are some RNA molecules with catalytic activity known as…
Correct answer: Most enzymes are proteins, but some are lipids- A. Koshland
- B. Robert Whittaker
- C. Emil Fischer
- D. Michael Menten
Explanation: Emil Fischer proposed the "lock and key" model, which suggests that enzymes and substrates have specific complementary shapes that allow…
Correct answer: Emil Fischer- A. Increasing
- B. Decreasing
- C. Remain constant
- D. Variable
Explanation: When the concentration of substrate molecules exceeds that of enzymes, the enzymes become saturated, meaning they are all occupied and…
Correct answer: Remain constant- A. Graph A
- B. Graph B
- C. Graph C
- D. Graph D
Explanation: Every enzyme works best at its optimum pH. Pepsin's optimum pH is 2. Graph D shows the correct optimal pH peak near pH 2, and it is the…
Correct answer: Graph D- A. Non-competitive
- B. Irreversible
- C. Competitive
- D. Isosteric
Explanation: Non-competitive inhibitors bind to an allosteric site, causing a conformational change in the enzyme that reduces its activity regardless…
Correct answer: Non-competitive- A. Transferases
- B. Isomerases
- C. Oxidoreductases
- D. Hydrolases
Explanation: The conversion of glucose 6-phosphate to fructose 6-phosphate is a glycolytic pathway reaction catalyzed by the enzyme phosphohexose…
Correct answer: Isomerases- A. Cyanide ion
- B. Hydrogen cyanide
- C. Cyanohydrins
- D. Cyano radical
Explanation: Amygdalin is a cyanogenic glycoside which contains a nitrile group. When it is acted upon by an enzyme called beta-glucosidase, it gets…
Correct answer: Hydrogen cyanide338. If the non-protien part is loosely attached to the protein part in the enzyme, it is known as _.
- A. Coenzyme
- B. Prosthetic group
- C. Cofactor
- D. Apoenzyme
Explanation: Prosthetic groups are compounds bound to enzymes by a covalent bond and their change from one form to another and back takes place in a…
Correct answer: Coenzyme- A. There is probably more substrate present than there is enzyme
- B. There is probably more product present than there is either substrate or enzyme
- C. The enzyme substrate complex is probably failing to form during the reaction
- D. There is probably more enzyme available than there is substrate
Explanation: When more substrate is added to already occurring enzymatic reaction and it is seen that activity has been increased this means that there…
Correct answer: There is probably more enzyme available than there is substrate- A. Increase in the rate of reaction
- B. Decrease in the rate of reaction
- C. First increase then decrease in rate of reaction
- D. First increase then constant rate of reaction
Explanation: The optimum temperature for the enzymes in the human body is 37˚C. When the temperature is increased from 30˚C, the rate of reaction is…
Correct answer: First increase then decrease in rate of reaction