BIO201 Connect 5

ATP is used in the cell to transfer energy. Indicate if the following statements about ATP are true or false. 1. When ATP is used in a reaction, the last phosphate is transferred to the substrate. 2. The release of the last phosphate from ATP is endergonic. 3. Once phosphates are released from ATP they can be added back in an endergonic reaction. 4. Creatine-P to creatine has a ΔG of -11kcal/mole and thus can be used to generate ATP from ADP. 5. When ATP is hydrolyzed to form ADP, the energy is released into the cytoplasm where enzymes use it to run endergonic reactions.

1. True 2. False 3. True 4. True 5. False

Rank these reactions from least to most energetically favorable. a. PEP to pyruvate, -14.8 kcal/mol b. ATP to ADP and Pi, -7.3 kcal/mol c. Glucose to Glucose-6-P, +3.3 kcal/mol d. Glucose-6-P to Fructose-6-P, +0.4 kcal/mol

1. c 2. d 3. b 4. a

A Biological Pathway Inhibiting one step in a biochemical pathway will not have any affect on the rates of the other reactions in the pathway.

False

Enzymes An enzyme binds the product more tightly than the substrate.

False

Feedback Inhibition If the end product of the biochemical pathway in the animation increases, it would eventually result in an increase in substrate 2.

False

You are cooking beans over a campfire. By the light of the fire, you read that one serving of beans is 120 calories. After eating the beans, you go for a hike along a stream. All of the items described here have energy. Identify the form of energy each contains.

POTENTIAL ENERGY -firewood -beans KINETIC ENERGY -flames -hiking -moving water

The reaction: ATP to ADP + Pi releases 7.3 kcal/mol of energy. For each reaction indicate how much ATP the reaction would require or generate.

REQUIRES 1 ATP -Glucose to G-6-P, +3.3 kcal/mol REQUIRES 2 ATP -Active transport of Na ion, +9.4 kcal/mol -Creatine to Creatine-P, +11 kcal/mol GENERATES AT LEAST 1 ATP -PEP to pyruvate, -14.8 kcal/mol -1,3 bisphosphoglycerate to glyceraldehyde-3-P, -12.5 kcal/mol

Cofactors In the example shown, which best describes the role of thiamine pyrophosphate in the reaction to cleave pyruvate? a. It behaves like a catalyst and is not consumed during the reaction. b. It behaves like a substrate and is not consumed during the reaction. c. It behaves like a substrate and is consumed during the reaction. d. It behaves like a catalyst and is consumed during the reaction.

a. It behaves like a catalyst and is not consumed during the reaction.

Enzymes: Sucrase What happens to sucrase when it binds to sucrose? a. Sucrase goes through a conformational change. b. Sucrase is cleaved in half. c. Sucrase releases energy to the sucrose. d. Sucrase becomes denatured.

a. Sucrase goes through a conformational change.

Feedback Inhibition Consider the biochemical pathway used to synthesize the amino acid proline. A large increase in the level of proline will most likely lead to a. a decrease in proline production. b. a further increase in proline production. c. increased breakdown of proline. d. proline being converted to praline. e. no change in the rate of proline production.

a. a decrease in proline production.

Your body needs amino acids to build new proteins encoded by your genes. Many of these amino acids come from your diet through the ____ of proteins you eat.

a. biosynthesis b. phosphorylation c. catabolism d. anabolism

A Biological Pathway If a chemical that inhibits Enzyme #3 was added to the system containing the biochemical pathway illustrated in the animation, which of the following would result? a. Product #1 would accumulate in the system. b. Product #2 would accumulate in the system. c. Substrate #1 would accumulate in the system. d. Substrate #1 would become depleted. e. Substrate #3 would accumulate in the system. f.. Product #4 would accumulate in the system. g. Substrate #4 would be depleted in the system. h. The final product would be depleted in the system.

b, e, g, h

A Biological Pathway Consider the biochemical pathway below, where A, B, and C are substrates and products and E1 and E2 are the enzymes that catalyze the reactions. If Enzyme 1 (E1) is inactive, which of the following compounds will accumulate? A-----[E1]----->B-----[E2]----->C a. B only b. A only c. B and C d. C only e. A and B

b. A only

Enzymes: Sucrase A mutation occurred in the gene that encodes the enzyme sucrase, resulting in a single amino acid substitution in the active site of the enzyme; a polar amino acid changed to a nonpolar amino acid. What is probably the result of this mutation. a. A single amino acid substitution will probably not affect the enzyme. b. Sucrase will not be able to bind sucrose in the active site. c. Sucrase will bind sucrose, but will not catalyze the hydrolysis reaction. d. Sucrase will no longer be specific to sucrose. It will now hydrolyze a variety of disaccharides.

b. Sucrase will not be able to bind sucrose in the active site.

A Biological Pathway Based on the animation, which of the following observations is true? a. Multiple final products were formed depending on which enzyme catalyzed the last reaction. b. The product from one reaction served as the substrate for the next reaction. c. Each enzyme was catalyzing the same reaction. d. Each enzyme only performed its reaction once. e. An enzyme could create different products depending on which substrate it started with.

b. The product from one reaction served as the substrate for the next reaction.

Cofactors Enzymes catalyze reactions by: a. adding energy to the reaction. b. lowering activation energy. c. raising activation energy. d. decreasing the entropy of the reaction.

b. lowering activation energy.

A Biological Pathway Consider the biochemical pathway below, where A, B, and C are substrates and products and E1 and E2 are the enzymes that catalyze the reactions. Enzyme 1 (E1) can utilize A-----[E1]----->B-----[E2]----->C a. only B as substrate. b. only A as substrate. c. neither A nor B as substrate. d. both A and B as substrates. e. either A or B as substrate, but not both.

b. only A as substrate.

Enzymes Which of the following binds most tightly to the active site of an enzyme? a. none of these choices are correct b. substrate c. any other enzyme d. water e. product

b. substrate

Feedback Inhibition In the example above, how does the final product of the pathway inhibit the pathway? a. By binding to the product of the first reaction. b. By binding to the active site of the first enzyme in the pathway. c. By binding to an allosteric site of the first enzyme in the pathway. d. By binding to the active site of the last enzyme in the pathway. e. By binding to the substrate of the first reaction.

c. By binding to an allosteric site of the first enzyme in the pathway.

Enzymes: Sucrase How often can a sucrase molecule be used to hydrolyze sucrose? a. once b. twice c. many times d. never

c. many times

Enzymes Most enzymes are a. polysaccharides. b. lipids. c. proteins. d. steroids. e. carbohydrates.

c. proteins.

Feedback Inhibition In feedback inhibition, the inhibitor of the biochemical pathway is often a. a product of another biochemical pathway. b. the substrate of the enzyme inhibited. c. the final product of the biochemical pathway. d. the product of the enzyme inhibited. e. a substance that is produced towards the middle of the biochemical pathway.

c. the final product of the biochemical pathway.

Enzymes: Sucrase Based on the reaction in the animation, what can you say about the change in free energy of the cleavage of sucrose into glucose and fructose? a. It is positive and the reaction is exergonic. b. It is negative and the reaction is endergonic. c. It is positive and the reaction is endergonic. d. It is negative and the reaction is exergonic.

d. It is negative and the reaction is exergonic.

Cofactors If thiamine pyrophosphate was not available to the enzyme in the animation which of the following would occur? a. The enzyme would use a different type of B vitamin as a coenzyme to catalyze the reaction. b. The enzyme would still be able to cleave pyruvate. c. The enzyme active site would not be open because of a lack of allosteric control. d. The enzyme would not be able to cleave pyruvate.

d. The enzyme would not be able to cleave pyruvate.

Cofactors What function do many B vitamins serve in the production of energy? a. They function as energy sources. b. They function as enzymes. c. They function as hypoenzymes. d. They function as co-enzymes.

d. They function as co-enzymes.

Enzymes An enzyme may catalyze a reaction by stressing or destabilizing the bonds of the substrates. This critical point in the enzymatic reaction is known as the a. Activation energy b. Change in free energy c. Energy state d. Transition state e. Enzyme-substrate complex

d. Transition state

Enzymes: Sucrase L-Arabinose is a naturally occurring, non-caloric sweetener that is a non-competitive inhibitor of sucrase. If L-Arabinose is consumed, what will happen to the Vmax of the reaction and Km of the substrate? a. Vmax and Km will both increase b. Vmax and Km will both decrease c. Vmax will not change, but Km will decrease d. Vmax will decrease, but Km will not change e. Vmax will decrease, and Km will increase

d. Vmax will decrease, but Km will not change

Enzymes: Sucrase Sucrase uses ____ to cleave sucrose into two monosaccharides. a. Fructose b. Oxygen c. Carbon dioxide d. Water e. Glucose

d. Water

Enzymes The enzyme in the animation is most likely catalyzing _____. a. a hydrolysis reaction. b. feedback inhibition. c. a catabolic reaction. d. an anabolic reaction. e. an endothermic reaction.

d. an anabolic reaction.