Chapter 5: Microbial Metabolism

The Calvin-Benson cycle would be considered to be primarily anabolic.

ANSWER: True

Some bacteria use electrons carried by NADH to generate light instead of ATP.

ANSWER: True ("Photobacterium" is a genus that switches the flow of electrons from NADH to a system that generates light.)

Bacteria use the process of amination when synthesizing amino acids.

ANSWER: True (Amination is the transfer of the amine group from one ammonia to form an amin acid. Transamination is the trasnfer of an amine group from amino acid to amino acid.)

During cellular respiration, carbon dioxide is produced only as a by-prodcut of acetyl-CoA synthesis and the Krebs cycle.

ANSWER: True (Carbon dioxide is produced whenever decarboxylation occurs in cellular respiration.)

A "holoenzyme" is a combination of an apoenzyme bound to its particular cofactor.

ANSWER: True (Many of these cofactors are organic molecules knwon as coenzymes.)

Bacterial proteases typically do their work outside the cytoplasmic membrane.

ANSWER: True (Proteases are usually secreted outside the cytoplasmic membrane to break down proteins, which are too large to enter the cell through the cytoplasmic membrane.)

Which process is INCORRECTLY matched with its location in bacteria?

ANSWER: beta-oxidation:mitochondria (Krebs cycle:cytoplasm...the Krebs cycle occurs in the cytoplasm.)

Bacteria can synthesize glycerol by reversing which pathway?

ANSWER: glycolysis (Gluconeogenesis is the synthesis of sugars from noncarbohydrate precurosrs.)

The activation energy of a chemical reaction _____.

ANSWER: is lower in the presence of an enzyme (Temperature can affect activation energy, but not really achieve it.)

ATP is made by substrate-level phosphorylation only during glycolysis.

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

An amphibolic reaction is one that is irreversible.

ANSWER: False (Amphibolic reactions are those that can proceed in either direction, thus are reversible.)

High temperatures break the covalent bonds that give enzymes their characteristic shapes, thereby denaturing them.

ANSWER: False (Denaturation of proteins occurs as high temperatures break "noncovalent" bonds such as hydrogen bonds.)

In feedback inhibition pathways, the end-product of the pathway is usually an inhibitor of the last enzyme in the pathway.

ANSWER: False (End-products that act as inhibitors of enzymes generally inhibit enzymes that are fairly early in the pathway.)

Fermentation results in the prodcution of carbon dioxide and water from pyruvic acid.

ANSWER: False (In fermentation, pyruvic acid is generally converted into organic waste products such as alcohol and lactic acid.)

The first compound formed in the Krebs cycle is oxaloacetic acid.

ANSWER: False (Oxaloacetic acid is the last compound formed in the Krebs cycle.)

Chloroplast structure features thylakoids arranged in stacks called stroma.

ANSWER: False (Thylakoid stacks in the chloroplast are called "grana", whereas the space between the thylakoid membrane and the outer membrane of the chloroplast is called the stroma.)

The carrier molecules in electron transport chains are all integral membrane proteins.

ANSWER: False (Ubiquinones are electron transport molecules that are lipid-soluble, nonprotein carriers.)

Which of the following best describes the function of a photosystem?

ANSWER: It absorbs light energy and converts it to ATP and NADPH. (A prton gradient is used to generate ATP and NADPH, not NADH.)

What is the purpose of the Calvin-Benson cycle?

ANSWER: It produces glyceraldehyde-3-phosphate by fixation of CO2 molecules.

What is the major function of fermentation?

ANSWER: It regenerates NAD+ for glycolysis. (Proton gradients are produced during cellular respiration, not fermentation.)

Which of the following is NOT a possible product of fermentation?

ANSWER: NADH (2,3-butanediol....this compound is produced by "Enterobacter" during fermentation.)

_____ is a cellular process that attaches a phosphate group to adenosine diphosphate using a high-energy bond.

ANSWER: Phsophorylation (Beta-oxidation....this term describes the catabolism of fatty acids.)

Which of these statements is NOT true of the electron transport chain?

ANSWER: The electron transport chain in eukaryotes is located on the outer mitochondrion membrane. (The electron transport chain creates a proton motive force that drives ATP synthesis...this is a correct statement about the electron transport chain.)

Enzymatic reactions reach a saturation point when the active sites of all enzymes present are occupied by substrate molecules.

ANSWER: True (This phenomenon is a limiting factor for all enzymatic reactions.)

Which of the following enzymes might be expected to catalyze the addition or removal of electrons associated with other molecules?

ANSWER: an oxidoreductase (This type of enzyme rearranges atoms within a molecule.)

The number of ATP molecules produced from the complete aerobic oxidation of one glucose molecule is given as a theoretical number because _____.

ANSWER: cells use proton gradients for processes other than ATP production

Many vitamins are important for metabolism because they act as _____.

ANSWER: coenzymes (holoenzyme...This is the combination of an apoenzyme and its cofactor.)

Sulfanilamide is a drug that interferes with bacterial enzymes in which of the following ways?

ANSWER: competitive inhibition

The active site of a chlorophyll molecule is structurally most similar to which of the following?

ANSWER: cytochromes (Although the active sites of chlorophylls and cytochromes are structurally similar, they differ in that chlorophylls use Mg2+ rather than the Fe2+ found in cytochromes.)

NAD+, FAD, and NADP+ are all examples of _____.

ANSWER: electron carriers (These molecules become changed in reactions, so are not enzymes.)

All of the following processes are ways that a cell can use a proton gradient EXCEPT _____.

ANSWER: electron transport (Proton gradients can be used for active transport, flagellar motion, and ATP production. Electron transport is a means by which a proton gradient is created, not used.)

Beta-oxidation is a method of catabolizing which of the following molecules?

ANSWER: fatty acids (Amino acids are catabolized by such methods as deamination.)

In eukaryotic cells, all of the following processes occur in the mitochondrion EXCEPT _____.

ANSWER: glycolysis (Beta-oxidation, the Krebs cycle, and electron transport all occur in the mitochondrion, while glycolysis occurs in the cytoplasm of the cell.)

Which of the following is NOT a possible form of regulation of metabolism in bacteria?

ANSWER: isolating enzymes within membrane-bound regions, such as lysosomes. (Bacteria are prokaryotes, thus do not have membrane-bound organelles.)

Folic acid is a precursor molecule necessary for the synthesis of which of the following?

ANSWER: nucleotides

Which of the following does NOT affect the activity of an enzyme?

ANSWER: oxygen concentration

Microbial fermentation can be detected in laboratory identification schemes by observing a change in _____.

ANSWER: pH (Common fermentation tests include pH indicators, which change colors as the pH of the test changes due to microbial fermentation.)

All of the following are associated with the process of glycolysis EXCEPT _____.

ANSWER: production of NADPH (Pyruvic acid is the final product of glycolysis.)

RuBP is an important part of which of the following pathways?

ANSWER: the light-independent reactions of photosynthesis (RuBP, which stands for ribulose 1, 5-bisphosphate, is necessary for carbon fixation during the Calvin-Benson cycle that occurs as part of the light-independent reactions of photosynthesis.)

Biological oxidations often involve which of the following?

ANSWER: the loss of a hydrogen atom (Oxidation does not always involve oxygen.)