ch 8 Energy and Enzymes

Which of the following statements is representative of the second law of thermodynamics? -Every energy transformation by a cell decreases the entropy of the universe. -Cells require a constant input of energy to maintain their high level of organization. -Without an input of energy, organisms would tend toward decreasing entropy. -Heat represents a form of energy that can be used by most organisms to do work. -Conversion of energy from one form to another is always accompanied by some gain of free energy.

Cells require a constant input of energy to maintain their high level of organization.

When chemical, transport, or mechanical work is done by an organism, what happens to the heat generated? -It is used to power yet more cellular work. -It is used to generate ADP from nucleotide precursors. -It is used to store energy as more ATP. -It is transported to specific organs such as the brain. -It is lost to the environment.

It is lost to the environment.

Why is ATP an important molecule in metabolism? -It provides energy coupling between exergonic and endergonic reactions -It is one of the four building blocks for DNA synthesis. -Its hydrolysis provides an input of free energy for exergonic reactions. -Its terminal phosphate bond has higher energy than the other two. -Its terminal phosphate group contains a strong covalent bond that, when hydrolyzed, releases free energy.

It provides energy coupling between exergonic and endergonic reactions.

Which of the following is true for all exergonic reactions? -The reactions are rapid. -The products have more total energy than the reactants. -The reaction proceeds with a net release of free energy. -A net input of energy from the surroundings is required for the reactions to proceed. -The reaction goes only in a forward direction: all reactants will be converted to products, but no products will be converted to reactants.

The reaction proceeds with a net release of free energy.

Which of the following is (are) true for anabolic pathways? -They consume energy to build up polymers from monomers. -They release energy as they degrade polymers to monomers. -They are usually highly spontaneous chemical reactions. -They consume energy to decrease the entropy of the organism and its environment. -They do not depend on enzymes.

They consume energy to build up polymers from monomers.

Which of the following is an example of potential rather than kinetic energy? the muscle contractions of a person mowing grass -the flight of an insect foraging for food -a molecule of glucose -light flashes emitted by a firefly -water rushing over Niagara Falls

a molecule of glucose

Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's -equilibrium point. -free-energy content. -entropy. -endothermic level. -activation energy

activation energy

How does a noncompetitive inhibitor decrease the rate of an enzyme reaction? -by changing the free energy change of the reaction -by binding at the active site of the enzyme -by acting as a coenzyme for the reaction -by decreasing the activation energy of the reaction -by changing the shape of the enzyme's active site

by changing the shape of the enzyme's active site

Zinc, an essential trace element for most organisms, is present in the active site of the enzyme carboxypeptidase. The zinc most likely functions as a(n) -cofactor necessary for enzyme activity. -noncompetitive inhibitor of the enzyme. -competitive inhibitor of the enzyme. -allosteric activator of the enzyme. -coenzyme derived from a vitamin.

cofactor necessary for enzyme activity.

Some of the drugs used to treat HIV patients are competitive inhibitors of the HIV reverse transcriptase enzyme. Unfortunately, the high mutation rate of HIV means that the virus rapidly acquires mutations with amino acid changes that make them resistant to these competitive inhibitors. Where in the reverse transcriptase enzyme would such amino acid changes most likely occur in drug-resistant viruses? such mutations could occur anywhere with equal probability -at an allosteric site -in regions of the protein that determine -packaging into the virus capsid -in or near the active site -at a cofactor binding site

in or near the active site