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Membranes > Fermentation > Flashcards

Fermentation Flashcards

1
Q

What is the difference between Fermentation and respiration?

A
  • fermentation has a lower ATP yield
  • no external electron acceptor therefore substrate has to be reduced and oxidised at the same time (redox disproportionation)
  • Electrons gained by the oxidation of the substrate is used to reduce another part of the substrate
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2
Q

What is substrate level phosphorylation?

A

directly phosphorylating ADP with a phosphate and energy provided from a coupled reaction

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3
Q

What is required or not required in substrate level phosphorylation?

A
  • no membrane required
  • no Fe required
  • can make exactly 1 ATP
    (excess delta G cant be used) (energy quantum is exactly 1 ATP)
  • only few reactions can be used (oxidative decarboxylation in glycolysis)
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4
Q

What is electron transport phosphorylation?

A
  • happens in respiration and fermentation
  • need electron transport chain from electron donor to electron acceptor
  • produces a proton or sodium motive force
  • needs membrane to establish conc gradient
  • have smaller energy quanta
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5
Q

What are the advantages of fermentation?

A
  • lack of oxygen or other electron acceptors
  • absence of Fe
  • faster throughput and generation of ATP growth
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6
Q

What are the disadvantages of fermentation?

A
  • lot less ATP produced
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7
Q

What is fermentation?

A

the chemical breakdown of a substance by bacteria, yeasts, or other microorganisms, not using an external electron acceptor

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8
Q

What are the advantages of respiration?

A
  • usually much higher ATP yield (depends on redox potential of e- acceptor)
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9
Q

What are the disadvantages of respiration?

A
  • longer metabolic pathway can make respiration slower
  • needs electron acceptor
  • needs Fe for cytochromes, FeS
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10
Q

What is respiration?

A

Oxidation of a substrate that is coupled to reduction of external electron acceptor

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11
Q

What is the solution for how during fermentation you cannot get rid of electrons?

A
  • oxidise one part of the substrate and reduce another

- can make extra ATP if can get rid of electrons as H2

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12
Q

Go over the pathway of ethanol fermentation by yeast.

A
  1. glycolysis occurs to produce pyruvate
  2. pyruvate becomes decarboxylated to generate acetaldehyde
  3. Acetaldehyde is reduced to ethanol
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13
Q

What are the products of ethanol fermentation in yeast?

A
  • carbon dioxide (oxidised)

- ethanol (reduced)

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14
Q

How does Zymomonas mobilis (bacterium) bypass the whole glycolysis step and create the pyruvate able to be fermented into ethanol?

A
  • oxidises glucose-6-phosphate

- splitting the oxidised product into G3P and pyruvate

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15
Q

How much ATP is made using the EMP pathway that yeast uses for glucose fermentation?

A

2 ATP

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16
Q

How much ATP is made using the EDP pathway that bacterium uses for glucose fermentation?

A

1 ATP

17
Q

Why does the bacterium not use the EMP pathway that yeast does?

A
  • it can grow as quickly as yeast due to the pathway being shorter
  • rate of ATP is therefore as good as yeast
18
Q

Go over the pathway of fermentation by Ruminococcus.

A
  1. glycolysis occurs to produce pyruvate
  2. NADH produced from pyruvate can be reduced to produce hydrogen
    - hydrogen conc needs to be kept low enough for this reaction to take place
  3. Pyruvate becomes decarboxylated to Acetyl-CoA
    BRANCHED (one oxidated and one reduced branch)
    one branch produces ethanol from acetyl coA to acetaldehyde to ethanol
    - this branch is used if NADH was not reduced in the previous step to H2.
    another branch produces acetate from acetyl coA to acetyl-P to acetate
    - this branch used if NADH was reduced in previous step
    - this branch also produces ATP (oxidated branch)
19
Q

How can you get 4ATP out of fermenting glucose in Ruminoccous albus?

A
  • get rid of electrons as hydrogens
  • oxidise all carbon to acetate and CO2
  • 1 ATP for every acetate made
  • reduce production of ethanol
20
Q

How do you transfer electrons from NADH to H2?

A
  • transfer electrons from NADh to reduce Ferredoxin (Fd)
  • replace NAD+ with Fd in the pyruvate decarboxylation step so its pyruvate:Fd not pyruvate-DH
  • use hydrogenase to produce H2 from reduced Fdred
21
Q

What do hydrogenase enzymes do? Link to structure

A
  • reduces protons to form hydrogens
  • 2H+ + 2e- —-> H2
  • contains Ni
  • some are proton pumps and are similar to complex 1
22
Q

What are the different mechanisms that can generate ATP?

A
  • sodium motive force (decarboxylation driven Na+ pump, Na+ driven ATP synthase)
  • light driven proton pump
  • product efflux couple proton translocation (lactic acid fermentation)
  • flavin based electron bifurcation

Membranes (19 decks)

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