bio ch 8 10 9

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

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 is true regarding metabolic pathways?

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

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.

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

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

The activation energy

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.

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.

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

feedback inhibition

Which of the following statements about enzymes is true?

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

Which of these statements about enzyme inhibitors is true?

The action of competitive inhibitors may be reversible or irreversible.

How does ATP drive transport work inside a cell?

By phosphorylating a transport protein

How does ATP drive mechanical work inside a cell?

By binding to motor proteins

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 reactions would be endergonic?

Glucose + fructose → sucrose

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.

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

What best characterizes the role of ATP in cellular metabolism?

The free energy released by ATP hydrolysis that may be coupled to an endergonic process via the formation of a phosphorylated intermediate.

Which of the following statements is correct regarding kinetic and potential energy?

Kinetic energy is associated with the relative motion of objects, and potential energy is the energy that matter possesses because of its location or structure.

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

releases energy when proceeding in the forward direction

Which of the following states the relevance of the first law of thermodynamics to biology?

Energy can be freely transformed among different forms as long as the total energy is conserved.

Which of the following statements is correct regarding competitive and noncompetitive enzyme inhibitors?

Competitive inhibitors bind to the active site of an enzyme while noncompetitive inhibitors bind to an enzyme away from the active site.

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.

What would the value of ΔS be for a chemical reaction in which a molecule is broken down into smaller components?

Positive

Which of the following statements correctly describes cofactors and coenzymes?

Both are nonprotein enzyme helpers; but most cofactors are metal ions, and coenzymes are organic molecules that are a specific type of cofactor.

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.

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

releases; absorbs

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.

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

releasing free energy that can be coupled to other reactions

Which of the following is an example of the second law of thermodynamics as it applies to biological reactions?

The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water.