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MICR2208 > 22 - Catabolism > Flashcards

22 - Catabolism Flashcards

1
Q

Fuel molecule

A

high energy molecules with energy stored in chemical bonds (e.g. glucose)

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2
Q

Glycolysis

A

Conversion of glucose to pyruvate.

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3
Q

TCA cycle

A

Conversion of pyruvate to CO2

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4
Q

what do all organisms require

A
  • Energy to make ATP
  • Electron source to make ATP
  • Carbon source to synthesise molecules
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5
Q

Catabolism

A
  • Larger, more complex molecules are broken down into smaller, simpler molecules with the release of energy
  • Fuelling reactions supply ATP, reducing power, and precursor metabolites
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6
Q

Anabolism

A

The synthesis of more complex molecules from simpler ones, with the input of energy

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7
Q

Important electron carrier pairs involved in catabolism

A
  • NAD+
  • FAD
  • Ubiquinone (coenzyme Q), flavoproteins, cytochromes
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8
Q

Why is ATP a high energy molecule

A

Because of the energy required to maintain the bonds between the bulky, negatively charged phosphate groups

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9
Q

What is the link between catabolism and anabolism

A

ATP

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10
Q

3 types of catabolism in chemoorganotrophs

A
  • Aerobic respiration (O2 as electron acceptor)
  • Anaerobic respiration (non O2 compound as electron acceptor)
  • Fermentation (Using organic compounds as electron acceptor)
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11
Q

3 steps of glucose catabolism

A
  1. Glycolysis (glucose –> pyruvate, produces ATP and NADH)
  2. TCA (Krebs) cycle (pyruvate –> CO2, produces ATP, NADH and FADH2)
  3. Electron transport chain (NADH, FADH2 –> ATP, O2 is terminal electron acceptor)
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12
Q

3 major pathways of Glycolysis

A
  1. Embden-Meyerhof pathway
  2. Pentose phosphate pathway
  3. Entner-Doudoroff pathway
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13
Q

Embden-Meyerhof pathway

A
  • Most common
  • Occurs in all major groups of microbes
  • Functions in the presence or absence of O2
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14
Q

Pentose phosphate pathway

A

-Alternative/complementary pathway for producing glycolysis intermediates

  • Most microbes have this
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15
Q

Entner-Doudoroff pathway

A
  • Some Gram-negative bacteria (e.g. Pseudomonas, Rhizobium)
  • Not used by eukaryotes of most Gram-positives
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16
Q

How are electrons harvested

A

NAD and FAD form redox pairs with fuel molecules during fuel molecule catabolism

17
Q

Harvesting electrons as reducing power example

A

NAD+ acquires reducing power when it reacts with malate in the TCA cycle. Malate is oxidised (loses electron) and NAD+ is reduced (gains electron)

18
Q

4 step process of ATP being synthesised by oxidative phosphorylation

A
  1. Electrons harvested by electron carriers during fuel molecule degradation enter an ETC
  2. Passage of electrons through the ETC by a series of interlinked electron carrier pairs
  3. Generation of a proton motive force from the electron transport chain
  4. Formation of ATP using the proton motive force by ATP Synthase
19
Q

What determines free energy released in ETC

A

The difference in reduction potential between the electron carrier redox pair and the terminal
electron acceptor redox pair

20
Q

ATP yield of glycolysis (substrate level
phosphorylation)

A

2

21
Q

ATP yield of TCA cycle (substrate level
phosphorylation)

A

2

22
Q

ATP yield of ETC (oxidative phosphorylation)

A

28 (7 times more than substrate level)

23
Q

Total ATP yield (in eukaryotes) during aerobic respiration

A

32

24
Q

Why does anaerobic respiration yield less energy

A

As the standard reduction potential is less positive than for O2

25
Q

Dissimilatory nitrate reduction

A

Use of nitrate as a terminal electron acceptor makes it unavailable for other uses

26
Q

Denitrification

A

Reduction of nitrate to nitrogen gas causes a loss of soil fertility

27
Q

Fermentation

A

Pyruvate acts as an electron acceptor, which:
- Regenerates NAD+ (requirement for maintenance of glycolysis)
- Ensures ATP formation by SLP is maintained
- Produces a variety of fermentation byproducts

28
Q

Types of lactic acid fermentation

A

Homolactic and heterolactic

29
Q

Homolactic

A

Mostly lactate produced

30
Q

Heterolactic

A

Lactate + ethanol + CO2

31
Q

Types of fermentation

A
  • Lactic acid fermentation
  • Alcohol fermentation (ethanol)
  • Mixed acid (lactate)
    – Butanediol
32
Q

How much energy does fermentation yield

A

only yields ATP by substrate level phosphorylation.

Produces 2 ATP per molecule of glucose (compared to 32 ATP by aerobic respiration).

Therefore microbial growth much slower

33
Q

What delivers electrons to ETC

A

NADH and FADH2

MICR2208 (26 decks)

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