Free Enzymes as Biocatalysts MCQs with Answers
14 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.
14 questions · page 2 of 2
11. Milk is curdled in cheese making by the enzyme
- 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 stomach of young mammals. Amylase acts on starch, lipase on fats and pepsin on proteins generally. Industrial enzymes of this kind are chosen for one specific substrate.
Correct answer: rennin12. The rate of an enzyme catalysed reaction levels off at high substrate concentration because
- 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. At that point the enzyme concentration rather than the substrate is limiting, so adding more enzyme would raise the rate again. This saturation behaviour is one of the clearest differences between enzymes and inorganic catalysts.
Correct answer: all the active sites are occupied, so the enzyme is saturated13. A coenzyme differs from a cofactor in that a coenzyme is
- 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 zinc and magnesium ions are inorganic. A helper bound tightly and permanently is called a prosthetic group instead. This is why vitamin deficiencies cause such widespread metabolic effects.
Correct answer: an organic molecule, often derived from a vitamin14. An enzyme used to decompose the lipids into fatty acids in our alimentary canal is
- 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 bile salts have emulsified the fat. Amylase acts on starch and protease on protein, each enzyme being specific to one class of substrate. Urease breaks urea down and is found in bacteria and plants rather than the human gut.
Correct answer: Lipase