Chapter 8: Mastering Biology Dynamic Study Module

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

The activation energy

True or False: Metabolic pathways consist of a series of reactions, each catalyzed by a different enzyme.

True

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.

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

Anabolic; catabolic

At low temperatures, a particular enzyme catalyzes a reaction, but at a slow rate. At high temperatures, the enzyme is completely inactive. Explain 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.

________ bind to the active site of an enzyme while _________ inhibitors bind to an enzyme away from the active site.

Competitive inhibitors; non-competitive inhibitors

Which of the following states the relevance of the first law of thermodynamics to biology? 1. The total energy taken in by an organism must be greater than the total energy stored or released by the organism. 2. Photosynthetic organisms produce energy in sugars from sunlight. 3. Energy is destroyed as glucose is broken down during cellular respiration. 4. Living organisms must increase the entropy of their surroundings. 5. Energy can be freely transformed among different forms as long as the total energy is conserved.

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

If the entropy of a living organism is decreasing, what 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. What accurately defines energy coupling?

Exergonic reactions drive endergonic reactions.

Which of the following reactions would be endergonic? 1. HCl → H+ + Cl 2. ATP → ADP + Pi 3. C6H12O6 + 6 O2 → 6 CO2 + 6 H2O 4. Glucose + fructose → sucrose 5. All are correct.

Glucose + fructose → sucrose

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

Kinetic energy; potential energy

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

Positive

At low pH, a particular enzyme catalyzes a reaction at a high rate. At neutral pH, the enzyme is completely inactive. What 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.

True or False: Enzymes speed up the rate of the reaction without changing the ΔG for the reaction.

True

True or False: The action of inhibitors may be reversible or irreversible.

True

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

True

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

True

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

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

cofactors; coenzymes

Breaking bonds is always _______ because it _______ energy.

endergonic; requires

Forming bonds is always _______ because it __________ energy.

exergonic; releases

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

The energy in an ATP molecule is released through ______ of one of the _________.

hydrolysis; phosphate groups

Enzymes can ______ the activation energy of reactions, but they cannot change __________ because they cannot change _________.

lower; the equilibrium point; the net energy output

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

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

Which of the following is an example of the second law of thermodynamics as it applies to biological reactions? 1. All of the listed responses are correct. 2. None of the listed responses is correct. 3. All types of cellular respiration produce ATP. 4. Cellular respiration releases some energy as heat. 5. The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water.

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