Enzymes

Help Questions

AP Biology › Enzymes

Questions 1 - 10
1

Which model of enzyme substrate binding posits that there is a transition state that develops before the reactants undergo change

Catalysis

Lock and key

Induced fit

Conformational change

Explanation

The lock and key model states that the active site of an enzyme precisely fits a specific substrate. The induced fit model states that the active site of an enzyme will undergo a conformational change when binding a substrate, to improve the fit.

2

Which is an example of a biological catalyst that is not a protein?

Ribozymes

Spliceosomes

Transferases

Hydrolases

Lyases

Explanation

This question ultimately hinges on knowing the difference between ribozymes and spliceosomes because transferase, hydrolase, and lyase should all be recognized as proteins that function as enzymes. Transferase catalyzes reactions that facilitate the transfer of functional groups. Hydrolase works to catalyze hydrolysis reactions. Lyase works to catalyze reactions that break down double bonds. Spliceosomes are a unit of proteins and RNA that work to catalyze reactions that splice out introns in RNA to form mature mRNA ready for translation. Ribozymes are important because they also splice RNA into mRNA, but they do not have a protein component to them. The discovery of Ribozymes was a breakthrough in that it was the first evidence that not all enzymes are proteins.

3

Which model of enzyme substrate binding posits that there is a transition state that develops before the reactants undergo change

Catalysis

Lock and key

Induced fit

Conformational change

Explanation

The lock and key model states that the active site of an enzyme precisely fits a specific substrate. The induced fit model states that the active site of an enzyme will undergo a conformational change when binding a substrate, to improve the fit.

4

Which is an example of a biological catalyst that is not a protein?

Ribozymes

Spliceosomes

Transferases

Hydrolases

Lyases

Explanation

This question ultimately hinges on knowing the difference between ribozymes and spliceosomes because transferase, hydrolase, and lyase should all be recognized as proteins that function as enzymes. Transferase catalyzes reactions that facilitate the transfer of functional groups. Hydrolase works to catalyze hydrolysis reactions. Lyase works to catalyze reactions that break down double bonds. Spliceosomes are a unit of proteins and RNA that work to catalyze reactions that splice out introns in RNA to form mature mRNA ready for translation. Ribozymes are important because they also splice RNA into mRNA, but they do not have a protein component to them. The discovery of Ribozymes was a breakthrough in that it was the first evidence that not all enzymes are proteins.

5

Which is an example of a biological catalyst that is not a protein?

Ribozymes

Spliceosomes

Transferases

Hydrolases

Lyases

Explanation

This question ultimately hinges on knowing the difference between ribozymes and spliceosomes because transferase, hydrolase, and lyase should all be recognized as proteins that function as enzymes. Transferase catalyzes reactions that facilitate the transfer of functional groups. Hydrolase works to catalyze hydrolysis reactions. Lyase works to catalyze reactions that break down double bonds. Spliceosomes are a unit of proteins and RNA that work to catalyze reactions that splice out introns in RNA to form mature mRNA ready for translation. Ribozymes are important because they also splice RNA into mRNA, but they do not have a protein component to them. The discovery of Ribozymes was a breakthrough in that it was the first evidence that not all enzymes are proteins.

6

At what pH does pepsin best function?

Explanation

Pepsin is an enzyme in the stomach that digests proteins. Because it is active in the stomach, which is highly acidic, pepsin best functions at a low pH between 2 and 2.5.

Pepsinogen is secreted by chief cells and converted into active pepsin after catalyzation by hydrochloric acid. The acid is secreted by parietal cells in response to gastrin secretion by G cells. After the stomach contents enter the duodenum of the small intestine, the acid is neutralized by bicarbonate secretions from the pancreas. This prevents the acid from damaging the walls of the small intestine.

7

The induced fit model better explains enzyme substrate binding than does the lock and key model. The induced fit model explains which of the following, that is not explained by the lock and key model

Broad specificity of enzymes

Narrow specificity of enzymes

Rigid structure of enzymes

Rigid structure of substrate

Explanation

The lock and key model states that the active site of an enzyme precisely fits a specific substrate. The induced fit model states that the active site of an enzyme will undergo a conformational change when binding a substrate, to improve the fit. The induced fit model accounts for the broad specificity of enzymes as the active site is not rigid, but can undergo a conformational change to better fit the substrate binding.

8

The induced fit model better explains enzyme substrate binding than does the lock and key model. The induced fit model explains which of the following, that is not explained by the lock and key model

Broad specificity of enzymes

Narrow specificity of enzymes

Rigid structure of enzymes

Rigid structure of substrate

Explanation

The lock and key model states that the active site of an enzyme precisely fits a specific substrate. The induced fit model states that the active site of an enzyme will undergo a conformational change when binding a substrate, to improve the fit. The induced fit model accounts for the broad specificity of enzymes as the active site is not rigid, but can undergo a conformational change to better fit the substrate binding.

9

What are the reactants of enzyme-catalyzed reactions known as?

Substrates

Enzymes

Inhibitors

Products

Explanation

The reactants of enzyme-catalyzed reactions are known as substrates. Enzymes catalyze formation of products from their substrates. Inhibitors hinder the efficacy of enzymes, thereby decreasing the rate of reactions, and nucleotides are the monomers of DNA and RNA.

10

At what pH does pepsin best function?

Explanation

Pepsin is an enzyme in the stomach that digests proteins. Because it is active in the stomach, which is highly acidic, pepsin best functions at a low pH between 2 and 2.5.

Pepsinogen is secreted by chief cells and converted into active pepsin after catalyzation by hydrochloric acid. The acid is secreted by parietal cells in response to gastrin secretion by G cells. After the stomach contents enter the duodenum of the small intestine, the acid is neutralized by bicarbonate secretions from the pancreas. This prevents the acid from damaging the walls of the small intestine.

Page 1 of 14