Unit 5 Learning Catalytics

Which of the following is true of enzymes?

1. Enzyme function is increased if the 3- D structure or conformation of an enzyme is altered.

2. Enzymes increase the rate of chemical reaction by providing activation energy to the substrate.

3. Enzyme function is independent of physical and chemical environmental factors such as pH and temperature.

4. Enzymes increase the rate of chemical reaction by lowering activation energy barriers.

4. Enzymes increase the rate of chemical reaction by lowering activation energy barriers.

During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a G of -20 kcal/mol. If you double the amount of enzyme in the reaction, what will be the Gfor the new reaction?

1. -20 kcal/mol

2. +20 kcal/mol

3. kcal/mol

4. -40 kcal/mol

1. -20 kcal/mol

                             

Activity of various enzymes at various temperatures (a) and at various pH (b).

Which temperature and pH profile curves on the graphs were most likely generated from analysis of an enzyme from a human stomach where conditions are strongly acid?

1. curves 1 and 4

2. curves 1 and 5

3. curves 3 and 4

4. curves 2 and 4

1. curves 1 and 4

A series of enzymes catalyze the reaction X → Y Z → A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme.


With respect to the enzyme that converts X to Y, substance A functions as _____.

1. the substrate

2. competitive inhibitor

3. an intermediate

4. an allosteric inhibitor

4. an allosteric inhibitor

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The function of mechanical digestion is to break down large chunks of food into smaller pieces. Why is this important? Smaller pieces of food _____.

1. have more surface area for chemical digestion than do larger pieces of food

2. do not taste as good as larger pieces of food

3. are easier to excrete than are larger pieces of food

4. are more easily stored in the stomach than are larger pieces of food

1. have more surface area for chemical digestion than do larger pieces of food

Stomach cells are moderately well adapted to the acidity and protein-digesting activities in the stomach by having _____.

1. cell wall impermeable to acid

2. sufficient colony of H. pylori

3. thick, mucous secretion and active mitosis of epithelial cells

4. high level of secretion of enzymes by chief cells

3. thick, mucous secretion and active mitosis of epithelial cells

The absorption of fats differs from that of carbohydrates in that _____.

1. carbohydrates need to be emulsified before they can be digested, whereas fats do not

2. fats, but not carbohydrates, are digested by bacteria before absorption

3. most absorbed fat first enters the lymphatic system, whereas carbohydrates directly enter the blood

4. fat absorption primarily occurs in the stomach, whereas carbohydrates are absorbed from the small intestine

3. most absorbed fat first enters the lymphatic system, whereas carbohydrates directly enter the blood

In a healthy person, after a large meal, the production of _____ will increase. After fasting, the production of _____ will increase.

1. insulin; glucagon

2. glucagon; glucose

3. glucagon; pepsinogen

4. trypsin; trypsinogen

1. insulin; glucagon

Biological systems use free energy based on empirical data that all organisms require a constant energy input. The first law of thermodynamics states that energy can be neither created nor destroyed. For living organisms, which of the following statements is an important consequence of this first law?

 

1. The energy content of an organism is constant except for when its cells are dividing.

2. The organism must ultimately obtain all the necessary energy for life from its environment.

3. The entropy of an organism decreases with time as the organism grows in complexity.

4. Organisms are unable to transform energy from the different states in which it can exist.

2. The organism must ultimately obtain all the necessary energy for life from its environment.