Deck 7: Metabolism and Growth

Question 1

In a coupled reaction:

A) a catabolic exergonic reaction supplies the energy needed for an anabolic endergonic reaction to occur.
B) a catabolic endergonic reaction supplies the energy needed for an anabolic exergonic reaction to occur.
C) an anabolic endergonic reaction supplies the energy for a catabolic exergonic reaction to occur.
D) an anabolic exergonic reaction supplies the energy for a catabolic endergonic reaction to occur.

Answer 1

A

Question 2

Describe differences that would be seen in the growth curve of a facultative anaerobe that is grown in the presence of oxygen, and the same facultative anaerobe grown in the absence of oxygen.

Answer 2

Facultative anaerobes are able to grow in the presence or absence of oxygen. When oxygen is present, oxygen serves as the final electron acceptor in electron transport. ATP yield is relatively high. When oxygen is absent, facultative anaerobes rely on alternative final electron acceptors or on fermentation to produce ATP. ATP yield is relatively low. Because growth rate is to some degree dependent on ATP production, growth rate will be faster in the presence of oxygen than in its absence. Consequently, if growth curves were constructed for the facultative anaerobe growing in the presence or absence of oxygen, the lag phase would be longer and the log phase would be less steep when oxygen is not present.

Question 3

During the stationary phase of microbial growth:

A) cells are preparing to divide.
B) production of new cells exceeds cell death.
C) production of new cells is approximately equal to cell death.
D) there is no production of new cells or cell death.
E) cell death exceeds the production of new cells.

Answer 3

C

Question 4

When cells catabolize biological molecules for the purposes of ATP production, energy in the biological molecule is released in a large number of small steps, rather than in a single large step. Why is this necessary?

Question 5

If the final electron acceptor is not present, which of the following still occurs?

A) the pumping of protons across a membrane
B) the production of ATP by the ATP synthase complex
C) the final oxidation of biological molecules in the Krebs cycle
D) the release of electrons to components of the electron transport chain by NADH and FADH₂
E) fermentation

Question 6

Describe how ATP is produced in electron transport.

Question 7

A bacterial species never uses oxygen as a final electron acceptor. However, it has the enzymes necessary to degrade toxic forms of oxygen. Such a bacterial species is an example of:

A) an obligate aerobe.
B) an obligate anaerobe.
C) a facultative anaerobe.
D) an aerotolerant anaerobe.
E) a microaerophile.

Question 8

In a particular redox reaction, when an electron pair is transferred from molecule X to molecule Y:

A) the transferred electrons were at greater energy and reduced stability with molecule X.
B) the electrons have greater energy and reduced stability with molecule Y.
C) the electrons had greater energy and stability with molecule X.
D) the electrons have greater energy and stability with molecule Y.
E) molecule X is reduced.

Question 9

Bacteria that grow well only at very low temperatures are termed:

A) extreme thermophiles.
B) mesophiles.
C) thermophiles.
D) psychrophiles.
E) psychotolerant.

Question 10

In the presence of the final electron acceptor, what happens to the NADH that is producedin glycolysis?

A) It is further reduced in the Krebs Cycle.
B) It is oxidized in electron transport.
C) It is converted into pyruvate.
D) It is released as a metabolic waste product.
E) It is converted into FADH₂.

Question 11

A photoautotroph is a microorganism that uses ________ as its carbon source and ________ as its energy source.

A) organic molecules; organic molecules
B) inorganic molecules; organic molecules
C) CO₂ ; inorganic molecules
D) CO₂; sunlight

Question 12

Why is pyruvate reduced during fermentation?

A) to regenerate NAD⁺, permitting glycolysis to continue
B) to produce additional NADH, which can be oxidized in electron transport
C) to produce additional ATP by coupling ATP production to the reduction of pyruvate. The now reduced form of pyruvate can then enter the Krebs Cycle.
D) Pyruvate is toxic to cells. It is therefore reduced to a non-toxic form.

Question 13

A chemically defined medium is often required to grow ________ bacteria in the laboratory.

A) fastidious
B) non-fastidious
C) acidophilic
D) halophilic
E) microaerophilic