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MICRB 265 > 5-3: Catabolism > Flashcards

5-3: Catabolism Flashcards

1
Q

How is metabolism modular

A

Set of interconnected modules
Metabolites are shuttled into limited number of pathways for energy generation and key biosynthesis rxns

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2
Q

What are the three ways to generate ATP

A
  1. Substrate level phosphorylation
  2. Oxidative phosphorylation
  3. Photophosphorylation
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3
Q

What is substrate level phosphorylation?

A

ATP generated as a product of an exergonic reaction

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4
Q

What is oxidative phosphorylation?

A

Energy generated from electron transfer reactions generates a PMF, which is then used to make ATP

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5
Q

What is photophosphorylation?

A

Energy captured from light is used to make a PMF, which is used to generate ATP

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6
Q

What is the preferred energy source of chemoorganotrophs

A

Sugars like glucose

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7
Q

Is it just glucose that can be used to generate energy?

A

No, many other organic compounds can also be used. Other sugars can be converted to glucose or intermediate of glycolysis/CAC

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8
Q

Why does direct combustion of glucose in cells not occur?

A

High activation energy and the reaction would release too much energy all at once

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9
Q

Glycolysis is conserved in what domains?

A

All domains of life

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10
Q

Does glycolysis require oxygen

A

NO

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11
Q

What two pathways can glycolysis be followed by?

A

Respiration or fermentation

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12
Q

What are the energy investment steps of glycolysis

A

ATP required at steps one and three

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13
Q

What step produces two 3C molecules

A

Step four

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14
Q

How much ATP is generated during glycolysis

A

2 in, 4 out = Net 2

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15
Q

What is left at the end of glycolysis

A

Pyruvate, which still has lots of E

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16
Q

What is the net reaction for glycolysis?

A

Glucose + 2NAD+ + 2Pi + 2 ADP -> 2 pyruvate + 2NADH + 2ATP + 2H+ + 2H2O

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17
Q

What does glycolysis lack? How is this resolved?

A

Redox balance
Restored using fermentation or CAC (respiration)

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18
Q

Preferred pathway of chemoorganotrophs

A

Citric acid cycle (respiration)

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19
Q

What does the CAC require

A

available external electron acceptor

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20
Q

Citric acid cycle AKA

A

Kreb’s cycle, Tricarboxylic acid cycle

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21
Q

What is converted to what before entering the CAC

A

Pyruvate to acetyl-CoA

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22
Q

What can feed into the CAC

A

Sugars, other organic molecules (lipids, aa, etc)

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23
Q

Where does the CAC take place

A

mitochondria

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24
Q

Is the CAC only used for catabolic purposes

A

No, also provides key metabolic intermediates for anabolic rxns

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25
Q

Energy is extracted as what during the CAC via ____________

A

ATP, GTP
Substrate level phosphorylation

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26
Q

Explain the pyruvate to acetyl-CoA reaction

A

Pyruvate + NAD+ + CoA = Acetyl-CoA + NADH + CO2

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27
Q

What products are in the CAC

A

NADH, CO2, NADPH, GTP/ATP, CoA, FADH2

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28
Q

** know where products are made in CAC

A

ok

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29
Q

How many ATP are generated per pyruvate

A

1

30
Q

What goes into the CAC

A

Acetyl CoA + 2NAD+ + NADP+ + FAD + Pi + ADP + 2H2O

31
Q

What comes out of the CAC per pyruvate

A

2CO2 + CoA + 2NADH + NADPH + FADH2 + ATP + 2H+

32
Q

How many NADH and FADH2 are produced per glucose in the CAC

A

4 NADH, 2 FADH2
(glycolysis produces 2 pyruvate = 2 CAC cycles)

33
Q

Did the CAC solve the redox imbalance from glycolysis

A

No, made it worse

34
Q

Where does the electron transport chain take place

A

Cytoplasmic membrane

35
Q

How does the ETC solve the redox imbalance

A

Regenerate oxidized forms of electron carriers (NAD+)

36
Q

What is used to generate ATP in the ETC

A

Proton motive forces (protons pumped out of cell)

37
Q

General explanation of ETC

A

Electrons passed down series of e carriers with increasingly +ve reduction potentials, until terminal e acceptor is reduced

38
Q

Most efficient respiration? What is the terminal e acceptor?

A

Aerobic, O2

39
Q

Key electron carriers in the ETC

A

NADH dehydrogenase and flavoproteins ->
Iron-sulfur proteins ->
Quinones ->
Cytochromes ->

40
Q

Explain NADH dehydrogenase & flavoproteins

A

NADH dehydrogenase take NADH electrons, transfer two e to flavoprotein, which contains FAD/FADH2

41
Q

Explain quinones

A

Not proteins - small molecules
Accept 2 e, transfer to next carrier
Often link Fe/S protein to crytochromes

42
Q

Explain iron-sulfur proteins

A

Metal cofactors, often multiple in ETC

43
Q

Explain cytochromes

A

Proteins containing heme prosthetic groups
Variable reduction potentials
ETC contain multiple, last stop before terminal

44
Q

Electrons in ETC transferred from _______________ to _______________ to ________________

A

Lower reduction potential carriers
Higher reduction potential carriers
Final electron acceptor (O2 if aerobic)

45
Q

ETC needs a continuous source of what

A

Final electron acceptors, they get used up

46
Q

Order of complexes the electrons go to

A

Complex 1 OR 2
to complex 3, to complex 4

47
Q

Difference between complexes 1 and 2

A

Complex 1 starts with NADH = 4 more protons pumped per 2e = more E
Complex 2 starts with FADH2 (higher reduction potential) and pumps fewer protons

48
Q

How many protons are pumped per NADH

A

10

49
Q

Is oxygen the only terminal acceptor in the ETC

A

No, different ones for anaerobic respiration

50
Q

Examples of other common e acceptors

A

Nitrate (NO3) and sulfate (SO4 2-)

51
Q

How is the ETC diverse

A

Microbe can have multiple different ETC, sometimes simultaneous
Different terminal acceptors
Different energy sources feed into

52
Q

How does the ETC proton motive force generate ATP

A

ATP synthase

53
Q

General overview of ATP synthase

A

Protons flow back along gradient, generate mechanical energy which powers ADP -> ATP

54
Q

Parts of ATP synthase

A

F1 = connected to F0 through stalk
F0 = protons flow through, in membrane

55
Q

What powers addition of inorganic P to ADP

A

The conformational change of F1 driven by stalk rotation

56
Q

How many H+ are pumped to produce an ATP

A

~3.3

57
Q

How many ATP are produced by ETC / ATP synthase

A

ETC = 10 protons pumped
ATP synthasev= 3.3 protons per ATP

= 3 ATP per NADH

58
Q

Summary on slide 27

A

ok

59
Q

What do chemoorganotrophs do when glucose is not present

A

They are flexible, can use other organic molecules
Pathway called B-oxidation can convert f.a. to acetyl-CoA
A.a can be converted to entry points of CAC

60
Q

What is catabolite repression

A

When a better energy source (e.g. glucose) is around, enzymes using other energy sources are inhibited/not expressed

61
Q

E. coli is a facultative anaerobe, meaning?

A

Can live/grow with or without O2

62
Q

Under anaerobic conditions, e. coli respirates using

A

Nitrate or ferments

63
Q

How is redox balance restored after glycolysis

A

Fermentation or respiration

64
Q

How does fermentation generate ATP and redox balance

A

Substrate level phosphorylation
Excretion of reduced fermentation products (regenerates NAD+)

65
Q

Fermentation of glucose occurs under what conditions

A

Anaerobic

66
Q

***review fermentation slides (31-37)

A

ok

67
Q

Ethanol fermentation used for

A

Alcoholic beverages, bread

68
Q

What can microbes ferment

A

Wide range of organic compounds (glucose, f.a., a.a., purines/pyrimidines)

69
Q

Common theme of fermentation

A

Generate energy rich molecule than can be hydrolyzed to produce ATP, donate e to a metabolite (reduce it) and excrete it = redox balance

70
Q

How many ATP does lactic acid fermentation generate vs how many does aerobic respiration generate

A

lactic acid = 2
aerobic = 38

MICRB 265 (34 decks)

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