26. Prokaryotes

Unlike plant cell walls that contain cellulose, bacterial cell walls are composed of ___________.

Which of the following correctly describe the fermentation pathway? Select True or False for each statement.

T/FIt includes a reaction that oxidizes NADH to NAD⁺.

T/FIt synthesizes ATP by substrate-level phosphorylation.

T/FIt includes a reaction that reduces NAD⁺ to NADH.

T/FIt synthesizes electron acceptors, so that cellular respiration can continue.

A new organism has been discovered. Tests have revealed that it is unicellular, is autotrophic, and has a cell wall that contains peptidoglycan. Based on this evidence, it should be classified as a(n)

a. Alga.

b. Archaean.

c. Protist.

d. Bacterium.

The bacteria that cause tetanus can be killed only by prolonged heating at temperatures considerably above boiling. This suggests that tetanus bacteria

a. Have cell walls containing peptidoglycan.

b. Secrete endotoxins.

c. Are autotrophic.

d. Produce endospores.

The traditional tree of life (shown above) presents the three domains as distinct, monophyletic lineages. However, other hypotheses propose different views on the relationships among the Archaea, Bacteria, and Eukarya. In particular, the two-domain hypothesis—or eocyte hypothesis—is emerging as a well-supported alternative to the three-domain hypothesis. The eocyte hypothesis, illustrated below, suggests that eukaryotes evolved from eocytes (also known as the Crenarchaeota—a major lineage of the Archaea). Resolving the relationships among these ancient lineages is difficult, but it has profound implications on our understanding of the origin of eukaryotic cells.

The Bacteria and Archaea both include microscopic prokaryotes that lack membrane-bound nuclei. What criteria have led to the classification of these two groups as separate domains?

Researchers examined the relationship between gut microbiomes and depression. To do so, they collected fecal samples from people with depression and also a control group of individuals with no signs of depression. They then performed a fecal microbiota transfer (FMT) by adding the samples to rats that had no gut microbiota and examined behaviors associated with depression and anxiety as well as species of bacteria that ended up growing in the rats’ guts. The results are presented below. Graph (a) shows the rats’ interest in a pleasurable experience (drinking sugar water). Graph (b) shows the amount of time rats spent out in the open versus along the edge of an area (a sign of anxiety). Graph (c) shows the number of species observed in rats after FMT.

Patients from the depression group had relatively high levels of bacteria in the genus Paraprevotella (a Gram-negative bacterium) relative to the control group of patients. Which of the following is a structural difference between Paraprevotella and methicillin-resistant Staphylococcus aureus (MRSA), a Gram-positive bacterium?

a. Paraprevotella contains a thick layer of peptidoglycan in its cell wall and MRSA lacks peptidoglycan.

b. The plasma membrane of Paraprevotella is surrounded by a cell wall that contains a relatively thin layer of peptidoglycan and an outer membrane and MRSA cells are surrounded by cell walls with a relatively thick layer of peptidoglycan,

c. Paraprevotella produces endospores but MRSA does not.

d. Paraprevotella lacks a plasma membrane but MRSA cells are surrounded by two plasma membranes.

Which is (are) true concerning the cell wall of prokaryotes?

The peptidoglycan molecule is responsible for the:

The Gram stain works because of differences in the ________ of bacteria.

What is the function of the glycocalyx in bacterial cells?

__________ is the slime-like layer of polysaccharides on the outer surface of bacterial cells.

___________ are an organized layer of polysaccharides tightly anchored to the cell wall.

Which of the following is not a function of slime layers and capsules:

Which of these are true about pili?