Question

1. pepsin is a protein - digesting enzyme in the human stomach. antacids cause the ph of the stomach to increase and protein digestion becomes less efficient. what occurs to reduce the efficiency of protein digestion?

a. the active site of pepsin changes shape.
b. the antacids are dissolved by pepsin in the gastric juice.
c. the antacids break the covalent bonds within pepsin.
d. the concentration of pepsin increases.

1. which statement most accurately describes the induced fit model of enzyme function?

a. substrate binding is not dependent upon the shape of the active site
b. competitive inhibitors block the substrate from the active site
c. substrate binding slightly changes the shape of the active site
d. an enzyme creates a permanent bond with the substrate

1. two students conduct an experiment in which they measure the concentration of an enzyme in a test tube at 1 minute intervals over the course of an enzymatic reaction. each of the students makes a prediction about what will happen to the enzyme concentration as the reaction progresses. student 1 predicts that the concentration of the enzyme in the test tube will decrease as the reaction progresses. student 2 predicts that the concentration of the enzyme in the test tube will stay the same as the reaction progresses. which students prediction is correct, and why? (think checkout clerks)

a. student 1; enzymes are depleted as a reaction progresses.
b. student 1; enzymes are not depleted as a reaction progresses.
c. student 2; enzymes are depleted as a reaction progresses.
d. student 2; enzymes are not depleted as a reaction progresses. (depleted = used up)

1. a student conducts an experiment in which the complex molecule hydrogen peroxide (h₂o₂) is broken down into the simpler molecules h₂o and o₂. what kind of reaction is taking place?

a. an exergonic reaction
b. an endergonic reaction
c. a combustion reaction
d. a double displacement reaction

1. how do enzymes speed up chemical reactions?

a. by increasing activation energy
b. by increasing energy produced by the reaction
c. by reducing activation energy
d. by reducing energy produced by the reaction

1. in aerobic respiration, glucose (c₆h₁₂o₆) combines with oxygen (o₂) to yield carbon dioxide (co₂) and water (h₂o). what is the balanced chemical equation for this reaction? (which reaction demonstrates the law of conservation of mass?)

a. c₆h₁₂o₆ → co₂ + h₂o
b. c₆h₁₂o₆ + 6o₂ → 6h₂o
c. c₆h₁₂o₆ + o₂ → 6co₂ + 6h₂o
d. c₆h₁₂o₆ + 6o₂ → 6co₂ + 6h₂o

Explanation:

• Question 36: Enzymes like pepsin have an optimal pH for activity. Antacids raise stomach pH, changing the shape of pepsin's active - site, which reduces its efficiency.
• Question 37: In the induced - fit model, substrate binding slightly changes the shape of the enzyme's active site to better accommodate the substrate.
• Question 38: Enzymes are catalysts and are not used up (depleted) during a reaction, so their concentration remains the same as the reaction progresses.
• Question 39: Breaking down a complex molecule into simpler ones is an exergonic reaction as it releases energy.
• Question 40: Enzymes speed up chemical reactions by reducing the activation energy required for the reaction to occur.
• Question 41: The balanced chemical equation for aerobic respiration of glucose is \(C_6H_{12}O_6 + 6O_2

ightarrow6CO_2 + 6H_2O\), which follows the Law of Conservation of Mass.

Answer:

• 36. A. The active site of pepsin changes shape.
• 37. C. Substrate binding slightly changes the shape of the active site.
• 38. D. Student 2; enzymes are not depleted as a reaction progresses.
• 39. A. An exergonic reaction
• 40. C. By reducing activation energy
• 41. D. \(C_6H_{12}O_6 + 6O_2

ightarrow6CO_2 + 6H_2O\)