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BI374 Final > Fermentation > Flashcards

Fermentation Flashcards

1
Q

Define fermentation

A
  • anaerobic catabolism of organic compound which serves as electron donor and acceptor
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2
Q

Anaerobic prokaryotes re-oxidize ____ by respiration or _______.

A
  • NADH by fermentation
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3
Q

What does adding mineral oil do?

A
  • decreases O2 and inhibits growth of aerobic organisms
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4
Q

What happens in the absence of an external electron acceptor?

A
  • organic compounds can be catabolized ONLY by fermentation
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5
Q

only certain compounds are fermentable, what is required for most fermentations?

A
  • energy-rich organic intermediate formed that can yield ATP by substrate-level phosphorylation
  • redox balance
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6
Q

What is a means of disposing excess electrons?

A
  • production of H2, associated with presence of iron-sulfur protein ferredoxin
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7
Q

What is ferridoxin?

A
  • very low potential electron carrier
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8
Q

What is the transfer of electrons from ferredoxin to H2 catalyzed by?

A
  • hydrogenase
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9
Q

How do you protect from too much acidity?

A
  • remove electron acceptors
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10
Q

What is a key product of many fermentative processes?

A
  • pyruvate
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11
Q

What has fermentative metabolism?

A
  • acids and ethanol
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12
Q

What puts holes in swiss cheese?

A
  • propionibacterium
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13
Q

What are carbohydrate fermentations?

A
  • lactic
  • ethanol
  • butyric
  • mixed acid
  • propionic
  • homeoacetic
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14
Q

What does it mean that there is considerable diversity in fermentation?

A
  • product of one organisms fermentation is fermented by a second organism
  • some employ ion gradients as basis for energetics across membrane
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15
Q

What happens when inadequate energy is released?

A

Coupled to ATP synthesis directly by substrate-level phosphorylation

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16
Q

What compounds can still support growth of the organism with inadequate energy?

A
  • succinate and oxalate
17
Q

What ferments succinate?

A
  • propionigenium modestrum
18
Q

What does chemiosmotic ATP formation result from?

A
  • Na+ pump (decarboxylation of organic acids)
    -ex. decarboxylation of succinate coupled to export of sodium across cytoplasmic membrane
19
Q

What happens during oxalate decarboxylation?

A
  • decarboxylated to formate = build-up of proton motive force from exportation of formate
20
Q

Explain the anaerobic food chain

A
  • fermentation of amino acids, carbs, purines and pyrimidines to organic acids and alcohols followed by conversion to CO2, H2, and acetate
  • methanogens convert compounds to CH4 and CO2
21
Q

What is the fermentation pathway of Clostridium propionicum?

A
  • lactate oxidized to pyruvate
  • pyruvate oxidized to acetyl-CoA and CO2
  • acetyl-CoA converted to acetate and ATP by acetyl-P
  • lactate acquires CoA from propionyl-CoA
  • lactyl-CoA dehydrated to acrylyl-CoA –> reduced to propionyl-CoA
22
Q

What is the overall equation for fermentation of clostridium propionicum?

A
  • 2 lactate –> 2 propionate + acetate + CO2 + H2O (3ATP)
23
Q

What is the simplified pathway of fermentation of clostridium propionicum?

A
  • Lactate –> pyruvate = 3 ATP and acetate
  • feeds back on self, picks up CoA to generate propionate and CoA transfer
24
Q

How many moles of ATP per molecule of acetate are generated when bacteria are growing on glucose using the EMP pathway?

A
  • 2
25
Q

What does propionate fermentation by the Succinate-propionate pathway yield?

A
  • more ATP than acrylate pathway per mole propionate formed
26
Q

What are the characteristics of propionibacterium?

A
  • G+ve
  • anaerobic
  • non-spore forming
  • non-motile
  • rod
27
Q

What does acetate fermentation do?

A
  • generates acetate from different starting products
  • pyruvate feeds central metabolism
  • generates CO2 and ammonia = feeds other organisms
28
Q

What is syntrophism?

A
  • 2 organisms carry out chemical transformation that neither can complete individually
  • ex. nitrification (ammonia to nitrite, nitrite to nitrate)
29
Q

What does acetogenesis mean?

A
  • generation of acetate
30
Q

What does homofermentative mean?

A
  • single end product
31
Q

What does heterofermentative mean?

A
  • multiple end products
32
Q

what ferments glucose to lactate? what is it used as?

A
  • heterogenous group of anaerobes
  • only or major product of fermentation
33
Q

What does aerotolerant mean?

A
  • can tolerate presence of oxygen but not adapted to utilize it
34
Q

What makes gas during fermentative metabolism in the infant gut? what is better?

A
  • e. coli
  • bifidobacteria needed in gut
35
Q

What are the products of mixed acid fermentation?

A
  • succinate, lactate, acetate, ethanol, formate, CO2, H+
36
Q

What are enteric bacteria? give 3 examples

A
  • facultative anaerobes
  • e. coli., salmonella, shigella
37
Q

State and briefly describe 3 reasons why some microorganisms may use fermentative metabolism. Name 2 environmental niches where you may expect to find fermentative bacteria.

A
  • May be the only way they can attack or utilize nutrients
    -Environmental condition (no O2)
    - Absence of external electron acceptor (O2), organic compounds can only be catabolized by fermentation
    - Less energy produced but supports growth
  • Too much competition
    • Not enough resources for nutrition and survival any other way
  • Nature of compound
    • Easy for microorganism to utilize than others, some cannot be attacked
      Niches : gut of cow, wetland soil (ANOXIC AND DEVOID OF OXYGEN)

BI374 Final (12 decks)

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