26. Prokaryotes

What do some photosynthetic bacteria use as a source of electrons instead of water?

a. Oxygen (O₂)

b. Hydrogen sulfide (H₂S)

c. Organic compounds (e.g., CH₃COO⁻)

d. Nitrate (NO₃^-)

Photoautotrophs use

a. Light as an energy source and CO₂ as a carbon source

b. Light as an energy source and methane as a carbon source

c. N₂ as an energy source and CO₂ as a carbon source

d. CO₂ as both an energy source and a carbon source

What are organisms called that use inorganic compounds as electron donors in cellular respiration?

a. Phototrophs

b. Heterotrophs

c. Organotrophs

d. Lithotrophs

What does the chemiosmotic hypothesis claim?

a. ATP is generated using phosphates taken from intermediates in the electron transport chain.

b. ATP is generated using a phosphate gradient produced by glycolysis and the citric acid cycle.

c. ATP is generated using a proton-motive force that is produced by the electron transport chain.

d. Water is generated using electrons taken from NADH and FADH₂ and transported through the electron transport chain.

Which of the following statements is true?

a. Archaea and bacteria have identical membrane lipids.

b. The cell walls of archaea lack peptidoglycan.

c. Prokaryotes have low levels of genetic diversity.

d. No archaea are capable of using CO₂ to oxidize H₂, releasing methane.

In terms of nutrition, autotrophs are to heterotrophs as

a. Kelp are to diatoms.

b. Archaea are to bacteria.

c. Slime molds are to algae.

d. Algae are to slime molds.

Explain how feedback inhibition regulates metabolic pathways.

Which of the following involves metabolic cooperation among prokaryotic cells?

a. Binary fission

b. Endospore formation

c. Biofilms

d. Photoautotrophy

Which of the following describes a bacterium that lives in the human intestine and causes disease? (A)commensalist (B)decomposer (C)gut mutualist (D)symbiotic pathogen

Biologists often use the term 'energy source' as a synonym for 'electron donor.' Why?

Using what you have learned about changes in Gibbs free energy, would you predict the ∆G value of catabolic reactions to be positive or negative? What about anabolic reactions? Justify your answers using the terms 'enthalpy' and 'entropy.'

Streptococcus mutans obtains energy by oxidizing sucrose. This bacterium is abundant in the mouths of Western European and North American children and is a prominent cause of cavities. The organism is virtually absent in children from East Africa, where tooth decay is rare. Propose a hypothesis to explain this observation. Outline the design of a study that would test your hypothesis.