Chapter 5

Which of the following is NOT an example of metabolic regulation by a cell? A. Cells use allosteric sites on enzymes to control enzymatic activity. B. If two energy sources are available, cells use the more efficient energy source. C. Cells close all channels in the membrane if no energy sources are needed. D. Feedback inhibition prevents cells from producing products that are in abundance. Hint: Cells are able to respond to changing conditions.

C. Cells close all channels in the membrane if no energy sources are needed.

Oxygenic photosynthesis releases oxygen derived from __________. Hint: Review the early steps of photosynthesis.

water

What is the major function of fermentation? A. It regenerates NAD+ for glycolysis. B. It generates a proton gradient. C. D. Hint: Think about the conditions under which fermentation is carried out.

A. It regenerates NAD+ for glycolysis.

Folic acid is a precursor molecule necessary for the synthesis of which of the following? A. Nucleotides B. Amino Acids C. Cholesterol D. Glycerol Hint: Recall that cells use small molecules, often called precursor metabolites, as building blocks in the formation of macromolecules.

A. Nucleotides

Altering the environmental pH can inhibit microorganism growth due to __________. A. denaturation of enzymes B. hydrolysis of enzymatic substrates C. acidification of carbohydrates D. chelation of metal ions needed for glycolysis Hint: Altering the pH can affect the H-bonding in tertiary and quaternary structures of proteins.

A. denaturation of enzymes

NAD+, FAD, and NADP+ are all examples of __________. A. electron carriers B. cytochromes C. precursor metabolites D. enzymes Hint: Recall that these molecules are extremely important in cellular redox reactions.

A. electron carriers

A molecule that gains an electron from another molecule will experience __________ in its overall electrical charge. A. an increase B. an increase and then a decrease C. a reduction D. no change Hint: The negatively charged electron will make it "more negative."

C. a reduction

Feedback inhibition __________. A. is always a form of competitive inhibition B. requires a cofactor C. is a mechanism for controlling the actions of enzymes D. is not reversible Hint: Feedback inhibition slows or stops anabolic pathways when the product is in abundance.

C. is a mechanism for controlling the actions of enzymes

The activation energy of a chemical reaction __________. A. is eliminated in the presence of an enzyme plus a coenzyme B. is the same for all chemical reactions C. is lower in the presence of an enzyme D. can be achieved by lowering the temperature of a reaction Hint: Recall that activation energy is the amount of energy it takes to trigger a chemical reaction.

C. is lower in the presence of an enzyme

Which of following are INCORRECTLY paired? A. electron transport chain: three molecules of ATP per molecule of NADH B. Krebs cycle: three molecules of NADH C. glycolysis: two molecules of pyruvic acid per one molecule of glucose D. transition step: two molecules of acetyl-CoA per one molecule of pyruvic acid

D. transition step: two molecules of acetyl-CoA per one molecule of pyruvic acid

ATP is made by substrate-level phosphorylation only during glycolysis. True or False Hint: Substrate-level phosphorylation requires enzymes that recognize substrate and ADP.

False - A small amount of ATP is also made by substrate-level phosphorylation during the Krebs cycle.

Fermentation is more energy efficient than aerobic glucose metabolism. True or False Hint: One molecule of glucose may produce up to 34 molecules of ATP when cells use the electron transport chain in cellular respiration

False - Fermentation yields fewer ATP per molecule of glucose than aerobic glucose metabolism. Fermentation yields fewer ATP per molecule of glucose than aerobic glucose metabolism.

Fermentation results in the production of carbon dioxide and water from pyruvic acid. True or False Hint: Fermentation is the partial oxidation of sugar to release energy using a cellular organic molecule as an electron acceptor.

False - In fermentation, pyruvic acid is generally converted into organic waste products such as alcohol and lactic acid.

The carrier molecules in electron transport chains are all integral membrane proteins. True or False Hint: The categories of protein carriers in the electron transport chain are flavoproteins, metal-containing proteins, and cytochromes.

False - Ubiquinones are electron transport molecules that are lipid-soluble, nonprotein carriers.

Carbon dioxide is produced only as a by-product of acetyl-CoA synthesis and the Krebs cycle during cellular respiration True or False Hint: For every two carbons that enter the Krebs cycle, two are lost to the environment.

True - Carbon dioxide is produced whenever decarboxylation occurs in cellular respiration.

Acidic pH breaks the hydrogen bonds that give enzymes their characteristic shapes, thereby denaturing them. True or False Hint: Enzymes have an optimal pH because ions released may distort secondary and tertiary structure of proteins.

True - Protons interfere with low-energy hydrogen bonds.

Chemical reactions that can proceed in either a catabolic or an anabolic direction are known as _________ reactions. Hint: This term is similar to the same term that is used for molecules that have both polar and nonpolar regions.

amphibolic

A coenzyme __________. A. can be derived from a vitamin B. functions as an inhibitor of enzyme function C. is an inorganic part of an enzyme D. is a small accessory enzyme

can be derived from a vitamin

____________ phosphorylation is the process in which photosystem I works with photosystem II, and electrons are used to reduce NADP+ to NADPH. Hint: In cyclic phosphorylation, electrons return to the original reaction center after passing through the electron transport chain.

noncyclic

The photosynthetic membranes that are similar to mitochondrial membranes in both structure and function are called __________. Hint: These membranes are found within the chloroplast.

thylakoids