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Microbiology > Chapter 7B - Microbial Metabolism: Fermentation & Respiration > Flashcards

Chapter 7B - Microbial Metabolism: Fermentation & Respiration Flashcards

1
Q

What type of energy is used to accomplish work in the cell?

A

Chemiosmotic potential

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2
Q

The chemiosmotic potential that releases energy during ionic movement

A
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3
Q

Many active-transport reactions and the rotation of the prokaryotic flagellum are drivement by the movement of ________ down a concentraiton gradient.

A

Ions

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4
Q

The chemiosmotic potential that releases energy during ionic movement is due to the ________________ of the cell being more acidic and more positively charged relative to the ____________ of the cell.

A

Exterior

Interior

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5
Q

What are two ways in which a chemiosmotic potential can be made?

A
  1. Electron transport systems (respiratory or phototrophic cells)
  2. ATP synthase
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6
Q

A chemiosomotic potential can be made in two ways: electron transport chain or ____________, both of which pump ions across a membrane. However, ___________ can work in opposite direction, too.

A

ATP synthases/ATPases

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7
Q

The ______________ of the cell tends to be more positively charged and the _____________ of the cell tends to be less positively charged.

A

Surface

Inside

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8
Q

_____________________ is the movement of ions across a semipermeable membrane down their electrochemical gradients.

A

Chemiosomosis

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9
Q

_____________________ refers to catabolic reactions producing ATP in which organic or inorganic compounds are primary electron donors and organic or inorganic compounds are ultimate electron acceptors; oxidation of a compound occurs with a terminal electron acceptor that is usually accompanied with ATP synthesis via oxidative phosphorylation.

A

Respiration

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10
Q

________________________ refers to catabolic reactions producing ATP in which organic compounds serve as primary electron donor and electron acceptor; ATP is produced by substrate-level phosphorylation; and there is no need for external electron acceptors.

A

Fermentation

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11
Q

Is glycolysis a type of fermentation or respiration?

A

Fermentation

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12
Q

The simplest and probably the oldest form of energy metabolism is _____________________ in which ATP is generated by substrate-level phosphorylation and ATP synthase functions in the direction of ATP hydrolysis to generate a protonic potential.

A

Fermentation

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13
Q

What is the basic strategy of fermentation?

A

The transfer of inorganic phosphate to a high-energy organic compound that can then be used to create ATP via substrate-level phosphorylation

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14
Q

In order for substrate-level phosphorylation to occur via fermentation, the phosphate has to be added to the organic compound as a “low-energy” phosphate, like in __________________________, and then converted to a “high-energy,” like in phosphoenolpyruvate (PEP).

A

2-phosphoglycerate

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15
Q

Fermentation produces end products at the same average _____________ level as the substrates.

A

Redox

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16
Q

Do all fermentations require redox reactions?

A

No; there are a few that do not in which the chemistry is such that a substrate-level phosphorylation can occur without any oxidation of the organic substrate

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17
Q

Three different strategies are used to incorporate oxidation reactions into fermentation pathways. What are they?

A
  1. Part of the substrate molecule is oxidized and part of it is reduced
  2. The substrate is first oxidized and then the oxidized intermediate is reduced
  3. Two different substrates are used, one being oxidized and the other being reduced
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18
Q

What is the goal of homolactic fermentation?

A

To regenerate NAD+

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19
Q

In _______________________ fermentation, glucose is oxidized to pyruvate, producing ATP and NADH, and the NADH is reoxidized by reducing pyruvate to _____________.

A

Homolactic

Lactate

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20
Q

What is the goal of ethanol-acetate fermentation?

A

To produce ATP

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21
Q

In _____________________ fermentation, one branch produces ATP while the other reoxidizes NADH.

A

Ethanol-acetate

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22
Q

What is the goal of Strickland fermentation?

A

To produce ATP

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23
Q

In ____________________ fermentation, one amino acid (alanine in this case) is oxidized to produce ATP while another amino acid (glycine in this case) is reduced to reoxidize NADH).

A

Strickland

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24
Q

A common fermentation of the amino acid ___________________ involves non-oxidative or reductive rearrangements and cleavage to produce ornithine and the high-energy compound carbamoyl phosphate, which can transfer its phosphate to ADP.

A

Arginine

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25
Q

What is fumarate respiration?

A

A fermentation process in which fumarate reductase cataylzes the reduction of fumarate to succinate and pumps two H+ per fumarate reduced into the periplasm

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26
Q

________________ ______________________ pumps protons as it conveys electrons to fumarate, contributing to the protonic potential without expending ATP to do so.

A

Fumarate reductase

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27
Q

Why is respiration more efficient than fermentation?

A

Because it couples the oxidation of organic compounds to the reduction of a separate electron acceptor, usually oxygen. The presence of an electron acceptor separate from the organic substrate allows the latter to be oxidized completely, thus liberating more energy than if significant amounts of it have to be excreted by waste; furthermore, respiration involves an additional and highly effective mechanism of energy conservation: chemiosmotic energy conservation

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28
Q

______________________ is a type of chemotrophic energy metabolism in which most or all of the ATP is made by chemiosmotic means.

A

Respiration

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29
Q

What are the five general steps of respiration outlined in the textbook?

A
  1. Organic electron donors are oxidized and NAD+ is reduced to NADH
  2. NADH is reoxidized to NAD+ by transferring its electrons to the electron transport system
  3. A series of electron transfers among the components of the electron transport system generates energy to pump protons
  4. A terminal electron acceptor accepts electrons from the electron transport system, generating a reduced waste product
  5. The resulting protonic potential is used for ATP synthesis and other energy needs
30
Q

There are 4 complexes in respiration. What are their names?

A
  1. NADH dehydrogenase
  2. Fumarate reductase
  3. Cytochrome b/c complex
  4. Cytochrome c oxidase
31
Q

Which of the four complexes in respiration does not act as a proton pump?

A

Fumarate reductase

32
Q

Most of the soluble oxidation reactions of metabolism use the same electron acceptor: __________.

A

NAD+

33
Q

The electrone transport system consists of two to four separate complexes of protein. One of these complexes oxidizes a soluble organic compound, normally NADH: ______________________.

A

NADH dehydrogenase

34
Q

Another protein complex reduces oxygen to water: _________________.

A

Cytochrome c oxidase or complex IV

35
Q

A third protein complex constitutes a proton pump: ________________________________.

A

Cytochrome b/c complex or complex III

36
Q

Each of the proteins of the electron transport system has ___________________ groups that are responsible for carrying the electrons.

A

Prosthetic

37
Q

What are the most common prosthetic groups in proteins of the ETS?

A

Hemes

Iron-sulfur centers

38
Q

What are hemes?

A

Tetrapyrroles with an iron atom bound in their center; they are a cyclic ring system that contain an iron atom that can alternate between Fe(II) and Fe(III)

39
Q

In ___________________________, iron atoms are bound by the sulfhydryl groups of several cysteine residues.

A

Iron-sulfure centers

40
Q

What are electron transport proteins with heme prosthetic groups called?

A

Cytochromes

41
Q

In most electron transport proteins, as electrons pass through the protein, they cause conformational changes that result in _____________________________________________.

A

Protons being released on the outside of the membrane and then replaced from the inside

42
Q

How does transfer of electrons occur in ETS proteins?

A

Via small, mobile carriers, quinone and cytochrome c

43
Q

Which small, mobile carrier molecule mediates transfer from the dehydrogenase complex to the cytochrome b/c complex?

A

Quinone

44
Q

Which small, mobile carrier molecule mediates transfer of electrons from the cytochrome b/c complex to the oxidase complex?

A

Cytochrome c

45
Q

Many respiratory prokaryotes lack the cytochrome b/c complex as well as the periplasmic cytochrome c. How can these organisms be identified?

A

Oxidase test

46
Q

__________________ organisms have the cytochrome b/c complex and the soluble cytochrome c.

A

Oxidase-positive

47
Q

_____________________ organisms lack the cytochrome b/c complex and the soluble cytochrome c.

A

Oxidase-negative

48
Q

What is the terminal oxidase in oxidase-negative prokaryotes?

A

Quinol oxidase

49
Q

What is the oxidase complex found in oxidase-positive organisms?

A

Cytochrome c oxidase

50
Q

Many organisms that possess the cytochrome b/c complex, periplasmic cytochrome c, and cytochrome oxidase can also make quinol oxidase. Thus they have a ___________________ electron transport system.

A

Branched

51
Q

The ratios of various carriers in a branched ETS are often modulated in response to environmental conditions. In well-aerated conditions, the amount of quinol oxidase is ______, and the amounts of cytochrome b/c complex and cytochrome oxidase are ______.

A

Low

High

52
Q

In branched ETS, when oxygen is limited, quinol oxidase has a _________ affinity for oxygen than cytochrome oxidase and is therefore _______________________ at low oxygen concentrations.

A

Higher

More efficient

53
Q

Which organism did we discuss in class that has a branched ETS?

A

Paracoccus

54
Q

Under high oxygen, Paracoccus makes an oxidase-__________ ETS that pumps 10 H+ for each NADH oxidized.

A

Oxidase-positive

55
Q

Under intermediate oxygen, a _________ ETS is made with all components of both oxidase-positive and oxidase-negative chains.

A

Branched

56
Q

Under low oxygen, Paracoccus makes an oxidase-_________ electron transport chain that pumps six H+ per NADH.

A

Oxidase-negative

57
Q

Alternate dehydrogenase complexes are used for different compounds. ______________________________ is an alternate dehydrogenase complex that reduces quinone and is a TCA enzyme embedded in the cell membrane or mitochondrial membrane.

A

Succinate dehydrogenase

58
Q

____________________________ oxidizes succinate to fumarate.

A

Succinate dehydrogenase

59
Q

What is the prosthetic group in succinate dehydrogenase?

A

FAD

60
Q

The most common electron acceptor in respiration is oxygen; however, many prokaryotes are able to use nitrate or nitrite in the absence of oxygen. This process is called _______________________________________________ when nitrate is reduced to nitrite or ammonia.

A

Nitrate respiration

61
Q

Nitrate respiration dependes on an alternate oxidase confusingly called _________________________, which replaces the cytochrome oxidase or quinol oxidase under anaerobic conditions, allowing normal respiration in the absence of oxygen, so long as nitrate is present.

A

Nitrate reductase

62
Q

In nitrate respiration, ________________ serves as the terminal electron acceptor, using the membrane oxidase complex - nitrate reductase. The product, ______________, may be excreted or it may be further reduced to _______________ by a cytoplasmic ___________________________________ that does not conserve energy.

A

Nitrate (NO3-)

Nitrite (NO2-)

Ammoniua (NH3-)

Nitrite dehydrogenase

63
Q

When nitrate is reduced to the gaseous end-product N2, the process is called _______________________.

A

Denitrification

64
Q

Outline the denitrifcation process in Paracoccus.

A
  1. NADH is oxidized to NAD+ by complex I or NADH dehydrogenase
  2. Electrons are transferred to nitrate reductase, a quinol oxidase, where nitrate is converted to nitrite
  3. Electrons are transferred cytochrome b/c complex
  4. Electrons are transferred to cytochrome c and are carried to nitrite reductase, a cytochrome c oxidase, oxidizing NO2 to N2O
  5. Again electrons are transferred to cytochrome c and then nitrous oxide reductase, a cytochrome c oxidase, where N2O is converted to N2
65
Q

For nitrate respiration and denitrification, the anaerobic electron transport chain is a variant of the aerobic one, and the organisms that do this kind of anaerobic respiration are ____________________ _______________.

A

Facultative anaerobes

66
Q

For organisms that can engage in nitrate respiration and denitrification, they use their cytochrome oxidase or quinol oxidase to reduce oxygen under ________________ conditions while they repress nitrate reductase and other reductases. Under _______________ conditions, nitrate reductase, nitrite reductase, and so forth are derepressed and the organisms switch to ______________________ respiration.

A

Aerobic

Anaerobic

Anaerobic

67
Q

Can other compounds - besides nitrate - serve as terminal electron acceptors in anaerobic respirations?

A

Yes, there are many

68
Q

How many ATP are produced per NADH in Paracoccus assuming high oxygen concentrations?

A

~3.3 ATP per NADH

69
Q

How many ETS are present in E. coli?

A

Four

70
Q

The number of protons pumped in E. coli depends on the ETS present, which in turn depends on the concentration and ratios of dehydrogenases and oxidases present. These dehydrogenases and oxidases are “activated” or “repressed” depending on the concentration of _________________.

A

Oxygen

71
Q

Generally speaking, under what conditions is E. coli less efficient at pumping protons?

A

Low oxygen

72
Q
A

Microbiology (15 decks)

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