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Bacterial Physiology (BIOL 471) > Ch. 15 > Flashcards

Ch. 15 Flashcards

1
Q

What are the 4 unifying themes of fermentation?

A
  1. O2 is not needed
  2. Electron acceptor is usually either pyruvate or pyruvate derivative
  3. NADH must be oxidized to NAD+ without an ETC
  4. ATP yield per glucose is significantly reduced (no ETC)
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2
Q

Define fermentation.

A

A pathway in which NADH is reoxidized by metabolites produced by the pathway

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3
Q

What are fermentations named after?

A

The major end products they generate

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4
Q

What are the 6 main classes of carbohydrate fermentations?

A
  1. Lactic
  2. Ethanol
  3. Butyric
  4. Mixed acid
  5. Propionic
  6. Homoacetic
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5
Q

Why are strict anaerobes killed by oxygen?

A
  • Toxic products of oxygen reduction are produced when single electrons are added to oxygen sequentially
  • These toxic products accumulate in the cell
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6
Q

What toxic products are produced by oxygen reduction?

A
  • Hydroxyl radical (OH•)
  • Superoxide radical (O2-)
  • Hydrogen peroxide (H2O2)
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7
Q

Why don’t aerobic and aerotolerant organisms acumulate superoxide radicals or hydrogen peroxide, but strict anaerobes do?

A
  • Aerobes/aerotolerants have superoxide disumutase and catalase
  • Strict anaerobes don’t have these enzymes that break down the toxic products
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8
Q

What reaction does superoxide dismutase catalyze?

A

O2- + O2- + 2H2 –> H2O2 + O2

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9
Q

What reaction does catalase catalyze?

A

H2O2 + H2O2 –> 2H2O + O2

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10
Q

How do most fermenting bacteria make most or all of their ATP?

A

Substrate-level phosphorylations

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11
Q

How do anaerobes generate a Δp (needed for solute transport, motility, etc.)?

A
  1. Reversing membrane-bound ATPase
  2. Reducing fumarate
  3. Carrying out a periplasmic oxidation of electron donors
    - W. succinogenes
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12
Q

Explain what is happening in the figure (energy conservation in anaerobic bacteria).

A
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13
Q

Fermentation pathways themselves produce the electron acceptors for the electrons produced during oxidations. What are these electron acceptors called?

A

Electron sinks
- Because they dispose of the electrons removed during the oxidations
- The reduced products are excreted into the medium

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14
Q

What are fermentation processes categorized by? (as in what is their defining characteristic)

A

Excretion of large quantities of reduced organic compounds (alcohols, organic acids, solvents, hydrogen gas)

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15
Q

What is the anaerobic food chain?

A

The fermentation of amino acids, carbs, purines, and pyrimidines to organic acids and alcohols and the conversion of these compounds to CO2/CH4/H2
- By prokaryotes

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16
Q

What is the importance of the anaerobic food chain in the carbon cycle?

A

Regenerates gaseous carbon

17
Q

Some anaerobic bacteria use protons as the major electron sink. They include _____.

A

obligate proton-reducing acetogens

18
Q

Define/describe lactic acid bacteria.

A

A heterogeneous group of aerotolerant anaerobes that ferment glucose to lactate as the sole or major product of fermentation

19
Q

Lactic acid bacteria include what genera?

A
  • Lactobacillus
  • Sporolactobacillus
  • Streptococcus
  • Leuconostoc
  • Pediococcus
  • Bifidobacterium
20
Q

Where are lactic acid bacteria found?

A
  • Living on the skin of animals, in the gastrointestinal tract, and in other place (e.g. mouth and throat)
  • Some genera live in vegetation and in dairy products
21
Q

Lactic acid bacteria metabolize glucose only fermentatively and derive most of their ATP from ____.

A

substrate-level phosphorylation

22
Q

What are the 2 major types of lactate fermentation? What glucose metabolism pathway does each one use?

A
  1. Homofermentative
    - Glycolysis
  2. Heterofermentative
    - PPP
23
Q

What is the only product of homolactate fermenation?

A

Lactate

24
Q

In homolactate fermentation, bacteria use what pathway to oxidize glucose to pyruvate?

A

Glycolytic pathway

25
Q

Explain how bacteria use homolactate fermentation to produce lactate.

A
  • Bacteria use the glycolytic pathway to oxidize glucose to pyruvate
  • Results in 2 ATPs per mole of glucose via the oxidation of phosphoglyceraldehyde
  • The NADHs produced in the oxidative step are used to reduce the pyruvate, forming lactate
26
Q

What is the overall reaction of homolactate fermentation?

A

glucose + 2 ADP + 2 Pi –> 2 lactate + 2 ATP

27
Q

How much ATP is made per mole of lactate produced in homolactate fermentation?

A

1 ATP per mole of lactate produced
- Since ATP yield per pyruvate is 1

Bacterial Physiology (BIOL 471) (15 decks)

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