Chapter 3: Microbial Metabolism

Question 1

A microbe has a metabolic pathway in which NAD+ donates an electron to an electron transport chain and then the electron is transported to sulfur, producing H2S gas. This must be ___________

Answer 1

anaerobic respiration

Question 2

In _________, the electron acceptor is an organic molecule such as pyruvate.

Answer 2

fermentation

Question 3

In ___________, the terminal electron acceptor is oxygen.

Answer 3

aerobic respiration

Question 4

When an electron is added to a chemical, then the chemical has been _______ (and not oxidized).

Answer 4

reduced.

Question 5

If you traced the movement of an electron in purple bacteria, what would you find?

Answer 5

The electron would be reused repeatedly in photophosphorylation.

Question 6

The electron is reused repeatedly in photophosphorylation- _________

(purple bacteria)

The electron begins at _____ and returns to ________.

Answer 6

cyclic photophosphorylation
-P870
-P870

Question 7

P680 is the electron center in Photosystem II of ____________ in organisms with chlorophyll a (plants, green algae, and cyanobacteria). It is not found in purple bacteria

Answer 7

noncyclic photophosphorylation

Question 8

What types of energy conservation are possible in photosynthetic algae?

Answer 8

substrate-level phosphorylation, oxidative phosphorylation, and photophosphorylation.

Only photosynthetic organisms use photophosphorylation, in which light energy is used to produce adenosine triphosphate (ATP)

Question 9

A common carbon source for chemolithotrophs is __________

Answer 9

carbon dioxide

Question 10

Glucose and amino acids are carbon sources for _____________

Answer 10

chemoorganotrophs

Question 11

What can be concluded about anoxygenic phototrophs?

Answer 11

it could belong to several groups of bacteria– these are prototrophs that do not produce oxygen.

Question 12

_________ eukaryotes produce oxygen

Answer 12

phototrophic

Question 13

Which are the products of the aerobic breakdown of a single molecule of glucose?

Answer 13

6 CO2 + 6 H2O

Question 14

Why is it helpful for some cyanobacteria to have nitrogenase in a heterocyst?

Answer 14

The heterocyst provides an anoxic environment.

Nitrogenase requires a very low oxygen environment to function, well below atmospheric concentrations. Needs anoxic env. to function, but not for assembly.
N2 is obtained from the air and does not need to be actively pumped into heterocysts.

Question 15

_________ pump protons to maintain an acidic internal environment.

Answer 15

Lysosomes

Question 16

RuBisCO can react with carbon dioxide and with oxygen, so what do you predict would happen to a photosynthetic bacterial cell that relied on the Calvin cycle in an atmosphere with a very high oxygen concentration?

Answer 16

The cell would produce less glyceraldehyde-3-phosphate.

Question 17

Does an enzyme affect whether a reaction is exergonic or endergonic?

Answer 17

No, because enzymes lower the activation energy but do not affect the free energy change.

Question 18

What would happen if a cell using glycolysis lost the ability to regenerate NAD+?

Answer 18

The cell would die because glycolysis would cease once there was no remaining NAD+

Question 19

When NAD+ is reduced,_____ is formed. NADH then must be oxidized to form NAD+ to allow glycolysis and other reactions to continue.

Answer 19

NADH

Question 20

During ________, NADH donates an electron to an organic molecule (such as pyruvate) to regenerate NAD+ as NAD+ is needed for fermentation to continue.

Answer 20

fermentation

Question 21

What can you predict about a bacterial cell that is growing in the Antarctic?

Answer 21

It has a relatively high percentage of short chain and unsaturated fatty acids.

These adaptations help to maintain membrane fluidity at cold temperatures.

Question 22

Which domains include species capable of nitrogen fixation?

Answer 22

Bacteria and Archaea
There are no eukaryotic cells capable of nitrogen fixation.