Free Enzymes as Biocatalysts MCQs with Answers
41 Enzymes as Biocatalysts MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Enzymes are protein or RNA biocatalysts that lower activation energy without being consumed, and their active sites bind specific substrates. The topic covers the lock and key and induced fit models, effects of temperature, pH and substrate concentration, cofactors, enzyme specificity, and competitive versus non-competitive inhibition.
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- A. are used up in the reactions they catalyse
- B. raise the activation energy of a reaction
- C. supply energy to drive unfavourable reactions
- D. speed up reactions by lowering the activation energy and are recovered unchanged
Explanation: An enzyme provides an alternative pathway with a smaller energy barrier, so a far larger proportion of collisions are effective at body…
Correct answer: speed up reactions by lowering the activation energy and are recovered unchanged- A. the shape and chemistry of its active site
- B. its molar mass
- C. the temperature of the reaction
- D. the concentration of the substrate
Explanation: Only a substrate whose shape and charge distribution complement the active site can bind, which is why sucrase acts on sucrose but not on…
Correct answer: the shape and chemistry of its active site- A. the substrate evaporates
- B. the enzyme is denatured as the weak bonds holding its tertiary structure break
- C. the enzyme is used up faster
- D. the activation energy increases
Explanation: Heat disrupts the hydrogen and ionic interactions that hold the chain in shape, so the active site loses its precise geometry and can no…
Correct answer: the enzyme is denatured as the weak bonds holding its tertiary structure break- A. denaturing the enzyme permanently
- B. binding an allosteric site
- C. occupying the active site because it resembles the substrate
- D. lowering the temperature
Explanation: Substrate and inhibitor compete for the same site, so the inhibition can be overcome by increasing the substrate concentration and the…
Correct answer: occupying the active site because it resembles the substrate- A. increase enzyme activity uncontrollably
- B. are converted into proteins by the body
- C. supply too much energy to the cell
- D. bind to sulphur containing groups in enzymes and denature them irreversibly
Explanation: These ions attack the sulphydryl side chains of cysteine, breaking disulphide bridges and destroying the tertiary structure, so the…
Correct answer: bind to sulphur containing groups in enzymes and denature them irreversibly- A. alters the charges on the side chains, changing the shape of the active site
- B. changes the molar mass of the enzyme
- C. removes the substrate from the solution
- D. converts the enzyme into a carbohydrate
Explanation: Excess hydrogen or hydroxide ions interfere with the ionic and hydrogen bonds between side chains, distorting the active site so the…
Correct answer: alters the charges on the side chains, changing the shape of the active site- A. raising the temperature of the substrate
- B. binding the substrate at its active site and stabilising the transition state
- C. supplying energy to the reactants
- D. changing the equilibrium position
Explanation: Binding orients the substrate correctly and strains the bonds that are about to break, offering a lower energy route to the products.
Correct answer: binding the substrate at its active site and stabilising the transition state- A. far less efficient
- B. highly specific and effective at mild temperature and pH
- C. unaffected by temperature
- D. consumed during the reaction
Explanation: Enzymes achieve rate enhancements that industrial catalysts cannot approach and do so at body temperature and near neutral pH, but they…
Correct answer: highly specific and effective at mild temperature and pH- A. how many substrate molecules one enzyme molecule converts per unit time
- B. the number of enzymes in a cell
- C. the temperature at which it denatures
- D. its molar mass
Explanation: Carbonic anhydrase converts around 600,000 molecules of carbon dioxide per second, which is why the reaction in red blood cells is…
Correct answer: how many substrate molecules one enzyme molecule converts per unit time- A. It occupies most of the enzyme's surface
- B. It is a small region whose shape and charges complement the substrate
- C. It binds any molecule of similar mass
- D. It is destroyed after each reaction
Explanation: Only a few residues, often far apart in the primary sequence but brought together by folding, form the active site, which is why the whole…
Correct answer: It is a small region whose shape and charges complement the substrate- A. amylase
- B. rennin
- C. lipase
- D. pepsin
Explanation: Rennin, also called chymosin, clots the milk protein casein, which is the first step in cheese production and is also present in the…
Correct answer: rennin- A. the substrate begins to inhibit the enzyme
- B. all the active sites are occupied, so the enzyme is saturated
- C. the enzyme is denatured by the substrate
- D. the products stop the reaction
Explanation: Once every active site is engaged, adding more substrate cannot increase the rate, and the plateau reached is Vmax.
Correct answer: all the active sites are occupied, so the enzyme is saturated- A. an inorganic metal ion
- B. an organic molecule, often derived from a vitamin
- C. part of the polypeptide chain
- D. a type of substrate
Explanation: NAD, FAD and coenzyme A are organic helpers built from niacin, riboflavin and pantothenic acid respectively, whereas cofactors such as…
Correct answer: an organic molecule, often derived from a vitamin- A. Amylase
- B. Protease
- C. Lipase
- D. Urease
Explanation: Pancreatic lipase hydrolyses triglycerides into fatty acids and glycerol in the duodenum, working on the enormous surface created after…
Correct answer: Lipase- A. Zygology
- B. Zymology
- C. Zymurgy
- D. Zootaxy
Explanation: Zymology is the scientific study of fermentation, including the biochemical action of microorganisms and enzymes that convert sugars into…
Correct answer: Zymology- A. Zygology
- B. Zymology
- C. Zymurgy
- D. Zootaxy
Explanation: Zymurgy is the practical branch concerned with brewing, distilling and the industrial use of fermentation.
Correct answer: Zymurgy- A. yl
- B. ase
- C. one
- D. al
Explanation: Most enzyme names end in the suffix -ase, such as amylase, urease, and oxidase, often indicating the substance or reaction on which the…
Correct answer: ase- A. Non proteineous
- B. Proteineous
- C. sugars
- D. lipids
Explanation: Coenzymes are small, non-protein organic molecules that assist enzyme action, often by carrying electrons or chemical groups during a…
Correct answer: Non proteineous- A. Substrate
- B. Structure
- C. Temperature
- D. Pressure
Explanation: Enzyme specificity arises from the particular three-dimensional structure of its active site, whose shape and chemical groups fit certain…
Correct answer: Structure- A. Enzymes
- B. Substrate
- C. Lipids
- D. any of above
Explanation: Enzymes are biological catalysts, and most enzymes are proteins that speed up biochemical reactions without being consumed.
Correct answer: EnzymesEnzymes as Biocatalysts MCQs: common questions
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