Chapter 8 - An Introduction to Metabolism

As ATP begins to build up in a cell, metabolism slows down. How does this happen?

ATP acts as an allosteric inhibitor to many of the enzymes involved in metabolism, thus slowing their function.

Cells use ATP constantly, but ATP is considered a renewable resource. What process makes this possible?

ATP can be regenerated by the addition of a phosphate group to ADP.

Which of the following correctly states the relationship between anabolic and catabolic pathways?

Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways.

How does ATP drive mechanical work inside a cell?

By binding to motor proteins

How does ATP drive transport work inside a cell?

By phosphorylating a transport protein

First law of thermodynamics

Energy can be transferred and transformed, but it cannot be created or destroyed.

If the entropy of a living organism is decreasing, which of the following is most likely to be occurring simultaneously?

Energy input into the organism must be occurring to drive the decrease in entropy.

Which of the following statements about enzyme function is correct?

Enzymes can lower the activation energy of reactions, but they cannot change the equilibrium point because they cannot change the net energy output.

Which of the following statements about enzymes is true?

Enzymes speed up the rate of the reaction without changing the ΔG for the reaction.

The second law of thermodynamics states that ______

Every energy transfer or transformation increases the entropy of the universe.

The primary manner in which cells manage their energy resources in order to do work is called energy coupling. Which of the following statements accurately defines energy coupling?

Exergonic reactions drive endergonic reactions.

Which of the following is true regarding metabolic pathways?

Metabolic pathways consist of a series of reactions, each catalyzed by a different enzyme.

Which of these statements about enzyme inhibitors is true?

The action of inhibitors may be reversible or irreversible.

Which of the following is changed by the presence of an enzyme in a reaction?

The activation energy

Which of the following statements about the active site of an enzyme is correct?

The active site may resemble a groove or pocket in the surface of a protein into which the substrate fits.

Which of the following statements is correct regarding ATP?

The energy in an ATP molecule is released through hydrolysis of one of the phosphate groups.

At low pH, a particular enzyme catalyzes a reaction at a high rate. At neutral pH, the enzyme is completely inactive. What statement best explains the difference in how pH affects the function of this enzyme?

The enzyme is adapted for low pH but is denatured at neutral pH, leaving it nonfunctional.

An endergonic reaction ______

absorbs free energy from its surroundings and is nonspontaneous

The process of stabilizing the structure of an enzyme in its active form by the binding of a molecule is an example of __________.

allosteric regulation

Noncompetitive inhibitor

bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective

Competitive inhibitors _____

bind to the active site of an enzyme

ATP allosterically inhibits enzymes in ATP-producing pathways. The result of this is called __________.

feedback inhibition

Enzyme activity is affected by pH because __________.

high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site

Cofactors are _____

nonprotein enzyme helpers

Coenzymes are ____

organic cofactors such as vitamins

An exergonic reaction ______

proceeds with a net release of free energy and is spontaneous

An exergonic (spontaneous) reaction is a chemical reaction that __________.

releases energy when proceeding in the forward direction

An exergonic reaction __________ free energy, and an endergonic reaction __________ free energy.

releases; absorbs

In general, the hydrolysis of ATP drives cellular work by __________.

releasing free energy that can be coupled to other reactions

At low temperatures, a particular enzyme catalyzes a reaction, but at a slow rate. At high temperatures, the enzyme is completely inactive. What statement best explains the difference in how temperature affects the function of this enzyme?

At low temperatures, there is not enough free energy for the enzyme to function at a high rate, and at high temperatures, the enzyme is denatured, leaving it nonfunctional.