Chapter 13 Molecular Microbiology

Oxidative phosphorylation is a critical process for many living organisms. Which of the following is an example of oxidative phosphorylation? A. A eukaryotic cell produces ATP during glycolysis. B. A prokaryotic cell adds oxygen to an organic molecule that contains phosphate. C. A prokaryotic cell produces ATP during the light reactions of photosynthesis. D. A eukaryotic cell makes ATP using an electron transport chain with oxygen as the terminal electron acceptor.

A eukaryotic cell makes ATP using an electron transport chain with oxygen as the terminal electron acceptor.

Which chemical is produced by light energy as a direct result of photosynthesis?

ATP

Light is used to generate what two things during oxygenic photosynthesis?

ATP and NADPH

AcetylCoA is an important molecule. It is produced from pyruvate (a three-carbon molecule) by a transition reaction in many organisms (acetylCoA serves as a substrate for the Krebs Cycle, citric acid cycle, and tricarboxylic acid cycle). This transition reaction releases CO2. Additionally, many organisms that use fermentation produce fatty acids, sometimes using acetylCoA. Why is acetylCoA so important in the formation of fatty acids?

AcetylCoA consists of a two-carbon acetate with coenzyme A. It is the building block for fatty acids; two carbons at a time are added by adding acetylCoA during the process. So, organisms that produce acetylCoA during fermentation have a two-carbon molecule that can easily be used to build fatty acids and that can also allow ATP to be generated in the process.

The term "anaerobic respiration" is often used more broadly than is strictly accurate. Which of the examples below is the best example of anaerobic respiration? A. Purple bacteria use a type of photosynthesis that does not generate oxygen. B. An organism uses an electron transport chain with sulfur as the terminal electron acceptor. C. Many organisms use an electron transport chain with oxygen as the terminal electron acceptor to generate relatively large quantities of ATP. D. Lactic acid fermenters are able to generate energy in the absence of oxygen.

An organism uses an electron transport chain with sulfur as the terminal electron acceptor.

What was the first anoxic ammonia-oxidizing organism described?

Brocadia

How many electrons are required for the reduction of SO42- to H2S?

Eight

In the modified glycolytic pathway found in Pyrococcus furiosus, what is the immediate electron acceptor for the oxidation of glyceraldehyde-3-phosphate?

Ferredoxin

Which of the following organisms does NOT oxidize iron at neutral pH? A. Gallionella B. Leptothrix C. Ferroplasma D. Sphaerotilus

Ferroplasma

Which of the following choices best describes the path of electrons in chemolithotrophs that are growing in hydrogen gas? A. H2 → quinones → cytochrome acceptors → O2 B. H2 → O2 → quinones → cytochrome acceptors C. O2 → quinones → cytochrome acceptors → H2 D. H2 → cytochrome acceptors → quinones → O2

H2 → quinones → cytochrome acceptors → O2

Which of the following chemicals is NOT an electron donor for chemolithotrophy? A. H2O B. NH4+ C. HS- D. Fe2+

H2O

Which of the following sulfur compounds is NOT commonly used as an electron donor in chemolithotrophic metabolism? A. H2SO4 B. S2O32- C. SO D. H2S

H2SO4

After glycolysis occurs, many organisms move pyruvate into mitochondria and convert it to acetylCoA. AcetylCoA is important in regulating steps of aerobic respiration. Even without knowing exactly where it plays a role, it is possible to make an informed guess based upon knowing basic principles of metabolic regulation. Which of the following would be the most likely result of high concentrations of acetylCoA in a mitochondrion?

High concentrations of acetylCoA (a high acetylCoA/CoA ratio) inhibit pyruvate dehydrogenase.

Which of the following is NOT a characteristic of syntrophy? A. Energy conservation may involve substrate-level phosphorylation and/or oxidative phosphorylation. B. One or more products are continually removed from the reaction. C. Syntrophic organisms are highly specialized for exploiting energetically marginal reactions. D. It occurs in oxic environments.

It occurs in oxic environments. -Syntrophy involves metabolic cooperation between two different microbes.

The catabolism of lipids produces more energy per gram than the catabolism of carbohydrates or proteins. Why is this the case?

Living organisms break down carbohydrates, proteins, and lipids through oxidation. Because lipids are more reduced initially, more energy can be extracted during this process.

Consider the following two statements about photosynthesis: All photosynthesis produces oxygen. All phototrophs are also autotrophs. A. Only statement I is correct. B. Only statement II is correct. C. Both statements I and II are correct. D. Neither statement I nor II is correct.

Neither statement I nor II is correct. -Many phototrophic bacteria carry out anoxygenic photosynthesis and others are photoheterotrophs.

Some organisms are capable of using aerobic respiration or anaerobic respiration but use aerobic respiration preferentially. Why do they use aerobic respiration when possible?

Respiration with oxygen as a terminal electron acceptor generates more energy than respiration with other terminal electron acceptors.

If an organism used glycolysis (Embden-Meyerhof-Parnas pathway) but were unable to use fermentation or an electron transport chain, what problem would develop?

The available NAD+ would be converted to NADH and glycolysis would stop due to the lack of NAD+.

What would happen to an obligate aerobe if cytochrome oxidase were affected by an inhibitor?

The electron transport chain would stop functioning properly and the organism might die from lack of ATP.

How is oxygen generated during oxygenic photosynthesis?

Water is oxidized to produce O2 and electrons, which then reduce the oxidized P680 reaction center.

Who discovered the process of nitrification?

Winogradsky

During photosynthesis, what causes the special pair of bacteriochlorophyll a molecules to become a strong reductant?

absorption of light energy

Which of the following compounds is NOT a product of amino acid fermentation by Clostridium? A. fatty acids B. CO2 C. NH3 D. acetoin

acetoin

What autotrophic pathway is utilized by organisms that oxidize ammonia?

acetyl CoA pathway

Which of the following enzymes is a principle component of the acetyl-CoA pathway? A. RubisCO B. pyruvate dehydrogenase C. carbon monoxide dehydrogenase D. citrate synthase

carbon monoxide dehydrogenase

Which photosynthetic pigments are responsible for the brilliant red, purple, yellow, or brown colors of anoxygenic phototrophs? A. chlorophylls B. phycobilins C. carotenoids D. bacteriochlorophylls

carotenoids

What is the principal chlorophyll of higher plants, most algae, and the cyanobacteria?

chlorophyll a

What process is detrimental to soil productivity, yet beneficial for wastewater treatment?

denitrification

Of the following choices, how can most denitrifying prokaryotes be classified? A. obligate anaerobes B. microaerophiles C. facultative aerobes D. strict aerobes

facultative aerobes

Glycolysis is an extremely important and ancient metabolic process. The term is generally used to refer to the Embden-Meyerhof-Parnas pathway, but other processes can also be used that start with the same substrate and that produce ATP (e.g., the Entner-Douderoff pathway). What is the substrate that is used for the first step classic process?

glucose

Which catabolic pathway do mixed-acid fermenters, such as Escherichia coli, use in the fermentation of glucose?

glycolysis

What organisms grow at the lowest light intensities of all known phototrophs?

green sulfur bacteria

What is the name of the enzyme that oxidizes hydrogen for chemolithotrophic growth?

hydrogenase

The reduction of sulfate requires the participation of the enzyme hydrogenase. Where in the cell is this hydrogenase located?

in the periplasm

What are organisms called that obtain their energy from the oxidation of inorganic molecules and their carbon from organic sources?

mixotrophs

What type of enzyme is utilized in the first step of the aerobic oxidation of an aliphatic hydrocarbon?

monooxygenase

Photosynthesis in purple phototrophic bacteria begins when energy is transferred to what structure?

photoprotection

Which of the following pairs is matched correctly? A. photosystem I - P720 B. photosystem II - P680 C. photosystem I - P680 D. photosystem II - P700

photosystem II - P680

What are the light-harvesting structures of cyanobacteria and red algae called?

phycobilisomes

What is the chemical composition of the membranes of the polyhedral cell inclusions found in some Calvin cycle autotrophs?

proteins

How is ATP produced as a result of aerobic nitrification?

respiration

In the purple photosynthetic bacteria, what drives the formation of NADPH for autotrophic growth?

reverse electron transport

Which of the following is a periplasmic protein that is involved in the electron flow in iron oxidation? A. rusticyanin B. ATPase C. quinones D. ferredoxin

rusticyanin -It transfers electrons between cytochrome c in the outer membrane and cytochrome aa3 in the cytoplasmic membrane.

For which system of sulfur oxidation is there strong evidence for horizontal gene transfer? A. APS reductase system B. sulfite oxidase system C. sulfur bypass system D. sox system

sox system

What process creates a proton motive force during oxalate fermentation in Oxalobacter formigenes?

the import of the dicarboxylic acid oxalate that is coupled to the export of the monocarboxylic acid formate

If an organism can utilize multiple terminal electron acceptors during anaerobic respiration, which one provides the most energy? A. the one that is most abundant in the environment B. the one with the most electropositive redox couple C. the one with the most electronegative redox couple D. the one that is least abundant in the environment

the one with the most electropositive redox couple

What are the functions of the two Ralstonia eutropha hydrogenases?

the production of ATP and the production of NADH

Photosynthesis in purple phototrophic bacteria begins when energy is transferred to what structure?

the special pair

In addition to substrate-level phosphorylation, how is ATP generated in acetogenesis?

through the establishment of a sodium motive force as acetyl-CoA is synthesized

What are the net products of glycolysis (the Embden-Meyerhof-Parnas pathway)?

two molecules of pyruvate, two molecules of ATP, and two molecules of NADH