26. Prokaryotes

Which of the following correctly describe an exergonic reaction? Select True or False for each statement.

T/F The products have lower Gibbs free energy than the reactants.

T/F Activation energy is required for the reaction to proceed.

T/F The products always have lower entropy than the reactants.

T/F The reaction always occurs quickly.

Which of the following statements is not true?

a. Archaea and bacteria have different membrane lipids.

b. The cell walls of archaea lack peptidoglycan.

c. Only bacteria have histones associated with DNA.

d. Only some archaea use CO₂ to oxidize H₂, releasing methane.

How does pH affect enzyme-catalyzed reactions?

a. Protons serve as substrates for most reactions.

b. Energy stored in protons is used to drive endergonic reactions.

c. Proton concentration increases the kinetic energy of the reactants, enabling them to reach their transition state.

d. The concentration of protons affects an enzyme's folded structure and reactivity.

What factors determine whether a chemical reaction is spontaneous or not?

Evaluate these statements about Koch's postulates, which are used to establish a causative link between a specific microbe and a specific disease. Select True or False for each statement.

T/FThe microbe must be present in individuals suffering from the disease and absent from healthy individuals.

T/FThe microbe must be isolated and grown in pure culture.

T/FIf organisms from the pure culture are injected into a healthy experimental animal, the disease symptoms should appear.

T/FThe microbe does not have to be isolated from the experimental animal as long as the disease is present.

On examining cells under a microscope, you notice that they occur singly and have no evidence of a nucleus. These cells must belong to a

a. Domain Eukarya

b. Domain Bacteria

c. Domain Archaea

d. The Protista

e. More than one of the above could be correct

Plantlike photosynthesis that releases O₂ occurs in

a. Cyanobacteria

b. Archaea

c. Gram-positive bacteria

d. Chemoautotrophic bacteria

Which of the following prokaryotes is not pathogenic?

a. Chlamydia

b. Rhizobium

c. Streptococcus

d. Salmonella

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.

Early ideas on the classification of life recognized all organisms as belonging to one of two fundamental lineages—prokaryotes or eukaryotes. Is this view compatible with either of the hypotheses illustrated here? Explain.

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.

Other hypotheses for the tree of life present the Archaea as the ancestors to all other organisms. Sketch a phylogenetic tree that presents Bacteria and Eukarya as more closely related to each other than to Archaea, and that has Archaea as a sister group to Bacteria and Eukarya.

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.

Evaluate this statement: According to the two-domain hypothesis, all members of the domain Archaea are prokaryotes and therefore lack membrane-bound nuclei.

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.

What other types of evidence or features might be used to ascertain whether the tree of life is best represented according to the three-domain or the eocyte hypothesis?

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

An organism that requires an environment of high salt concentration describes an Extreme…