Biology Chapter 6

Determine if each statement about the molecule in the reaction is true or false. 1) Phosphoenolpyruvate is a product. 2) Mg2+ ion is a cofactor. 3) Pyruvate kinase is an enzyme. 4) Pyruvate is a substrate.

1) False 2) True 3) True 4) False

Rank these reactions from least to most energetically favorable.

1) Glucose to Glucose-6-P; +3.3 kcal/mol 2) Glucose-6-P to Fructose-6-P; +0.4 kcal/mol 3) ATP to ADP and Pi; -7.3 kcal/mol 4) PEP to Pyruvate; -14.8 kcal/mol

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 decrease in proline production

If E1 is inactive, which of the following compounds will accumulate?

A only

A hydrogen atom consist of

A proton and an electron

NAD+ is made from niacin, a B vitamin. Based on the animation, if someone is deficient in niacin, which of the following symptoms might they experience?

A reduction in energy

The enzyme in the animation is most likely catalyzing

An anabolic reaction

Energetic molecules such as NADH and ATP are often reactants of _____ reactions.

Anabolic

Which of the following statements about enzymes is true?

As more substrate is added, the reaction will continue to occur faster and faster.

In the example above, how does the final product of the pathway inhibit the pathway?

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

Energetic molecules such as NADH and ATP are often products of ____ reactions.

Catabolic

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.

Catabolism

Consider the biochemical pathways illustrated below. Product D will act as an allosteric inhibitor of what enzyme to regulate its own production? A__E1__B__E2__C__E3__D ............. l ........... E4 ............. l ............ E

E2

NAD+ is a coenzyme for many enzymes involved in redox reactions. This means that

Enzymes that use NAD+ as a coenzyme will not function properly if NAD+ is not available

RNA exposed to an _____ will release _____ which the cell can recycle.

Exonuclease, nucleotides

An enzyme binds the product more tightly than the substrate.

False

An enzyme catalyzes a chemical reaction in the cell, but can only be used once.

False

If the end product of the biochemical pathway increases, it will eventually result in an increase in Substrate 2.

False

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

False

The release of the last phosphate from ATP is endergonic.

False

When ATP is hydrolyzed to form ADP, the energy is released into the cytoplasm where enzymes use it to run endergonic reactions.

False

Consider the biochemical pathways illustrated in the last question. If product D is abundant, why is it preferable to inhibit E2 rather than E1?

Inhibition of E2 will prevent the production of D, but still allow synthesis of E

What happens when the coenzyme NAD+ gains an H atom?

It also gains an electron, causing it to be reduced

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?

It is negative and the reaction is exergonic

How often can a sucrase molecule be used to hydrolyze sucrose?

Many times

Where is sucrase found in the human body?

On the microvilli of the small intestine

Consider the biochemical pathway below, where A, B, and C are substrates and products and and E1 and E2 are the enzymes that catalyze the reactions. Enzyme 1 (E1) can utilize A__E1__B__E2__C

Only A as a substrate

In the reaction Pyruvate + NADH ---- Lactate + NADH+ , pyruvate is being ____ while NADH is being _____

Oxidized, reduced

Cells obtain energy by _____ food molecules such as glucose.

Oxidizing

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 Engery: 1) Firewood and 2) Beans Kinetic Energy: 1) Flames, 2) Hiking, and 3) Moving water

If a chemical that inhibits Enzyme #3 was added to the system, which of the following would result?

Product #2 would accumulate in the system Substrate #3 would accumulate in the system Substrate #4 would be depleted in the system The final product would be depleted in the system

Protein exposed to a _____ will release ____ which the cell can recycle.

Proteasome, amino acids

Enzymes are

Proteins

Molecules capable of enzymatic activity include

RNA and proteins

Which of the following binds most tightly to the active site of an enzyme?

Substrate

What happens to sucrase when it binds to sucrose?

Sucrase goes through a conformational change

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?

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

In feedback inhibition, the inhibitor of the biochemical pathway is often

The final product of the biochemical pathway

Based on the animation, which of the following observations is true?

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

An enzyme may catalyze a reaction by stressing or destabilizing the bonds of the substrates. This point in the enzymatic reaction is known as the

Transition state

ATP is used in the cell to transfer energy.

True

Creatine P to creatine has a (delta)G of -11 kcal/mol and thus can be used to generate ATP from ADP.

True

If the end product of the biochemical pathway increases, it will eventually result in an increase in Substrate 1.

True

In a biochemical pathway, the product released by the first enzyme becomes the substrate for the second enzyme.

True

Once phosphates are released from ATP, they can be added back in an endergonic reaction.

True

When ATP is used in a reaction, the last phosphate is transferred to the substrate.

True

Whenever a molecule is oxidized, another molecule must be reduced.

True

L-Arabinose is a naturally occurring, non-caloric sweetener that is a noncompetitive inhibitor of sucrase. If L-Arabinose is consumed, what will happen to the V-max of the reaction and the K-m of the substrate?

V-max will decrease but K-m will not change

Sucrase uses ____ to cleave sucrose in to two monosaccharides.

Water