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MICRB 265 > 5-3: Catabolism > Flashcards

5-3: Catabolism Flashcards

(72 cards)

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1
Q

How is metabolism modular

A

Set of interconnected modules
Metabolites are shuttled into limited number of pathways for energy generation, 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 the preferred energy source of chemoorganotrophs

A

Sugars like glucose

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4
Q

Only glucose 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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5
Q

Glucose is oxidized or reduced to CO2? Is it fast or slow?

A

Oxidation rxn
Slow and controlled, gradual breakdown into lower and lower energy molecules

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6
Q

Why is glucose to CO2 slow? What if it wasn’t?

A

High activation energy
If there wasn’t, a tremendous amount of energy would be released at once

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7
Q

Glycolysis is conserved in who?

A

All domains of life

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8
Q

Does glycolysis require oxygen

A

NO

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9
Q

Glycolysis has to be followed by

A

Respiration or fermentation

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10
Q

What are the energy investment steps of glycolysis

A

ATP required at steps one and three

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11
Q

What step produces two 3C molecules

A

Step four

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12
Q

Substrate level phosphorylation of what generates 2 ATP

A

1,3-bisphosphoglycerate followed by phosphoenolpyruvate

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13
Q

How much ATP is generated during glycolysis

A

2 in, 4 out = 2

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14
Q

What is left at the end of glycolysis

A

Pyruvate, which still has lots of E

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15
Q

Why does phosphoenolpyruvate release energy

A

High E phosphate bond broken to generate ATP

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16
Q

What happens to NAD+ or NADH at reaction six

A

NAD+ is reduced to NADH (redox rxn)

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17
Q

What goes into glycolysis

A

Glucose + 2NAD+ + 2Pi + 2 ADP

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18
Q

What comes out of glycolysis

A

2 pyruvate + 2NADH + 2ATP + 2H+ + 2H2O

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19
Q

What does glycolysis lack? How is this resolved?

A

Redox balance
Restored using fermentation or CAC (respiration)

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20
Q

Preferred pathway of chemoorganotrophs

A

Citric acid cycle (respiration)

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21
Q

What does the CAC require

A

available external electron acceptor

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22
Q

Citric acid cycle AKA

A

Kreb’s cycle, Tricarboxylic acid cycle

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23
Q

What is converted to what before entering the CAC

A

Pyruvate to acetyl-CoA

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24
Q

What can feed into the CAC

A

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

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25
Where does the CAC take place
mitochondria
26
Is the CAC only used for catabolic purposes
No, also provides key metabolic intermediates for anabolic rxns
27
Energy is extracted as what during the CAC via ____________
ATP, GTP Substrate level phosphorylation
28
Explain the pyruvate to acetyl-CoA reaction
Pyruvate + NAD+ + CoA = Acetyl-CoA + NADH + CO2
29
What products are in the CAC
NADH, CO2, NADPH, GTP/ATP, CoA, FADH2
30
** know where products are made in CAC
ok
31
How many ATP are generated per pyruvate
1
32
What goes into the CAC
Acetyl CoA + 2NAD+ + NADP+ + FAD + Pi + ADP + 2H2O
33
What comes out of the CAC per pyruvate
2CO2 + CoA + 2NADH + NADPH + FADH2 + ATP + 2H+
34
How many NADH and FADH2 are produced per glucose in the CAC
4 NADH, 2 FADH2 (glycolysis produces 2 pyruvate = 2 CAC cycles)
35
Did the CAC solve the redox imbalance from glycolysis
No, made it worse
36
Where does the electron transport chain take place
Cytoplasmic membrane
37
How does the ETC solve the redox imbalance
Regenerate oxidized forms of electron carriers (NAD+)
38
What is used to generate ATP in the ETC
Proton motive forces (protons pumped out of cell)
39
General explanation of ETC
Electrons passed down series of e carriers with increasingly +ve reduction potentials, until terminal e acceptor is reduced
40
Most efficient respiration? What is the terminal e acceptor?
Aerobic, O2
41
Key electron carriers in the ETC
NADH dehydrogenase and flavoproteins -> Iron-sulfur proteins -> Quinones -> Cytochromes ->
42
Explain NADH dehydrogenase & flavoproteins
NADH dehydrogenase take NADH electrons, transfer two e to flavoprotein, which contains FAD/FADH2
43
Explain quinones
Not proteins - small molecules Accept 2 e, transfer to next carrier Often link Fe/S protein to crytochromes
44
Explain iron-sulfur proteins
Metal cofactors, often multiple in ETC
45
Explain cytochromes
Proteins containing heme prosthetic groups Variable reduction potentials ETC contain multiple, last stop before terminal
46
Electrons in ETC transferred from _______________ to _______________ to ________________
Lower reduction potential carriers Higher reduction potential carriers Final electron acceptor (O2 if aerobic)
47
ETC needs a continuous source of what
Final electron acceptors, they get used up
48
Order of complexes the electrons go to
Complex 1 OR 2 to complex 3, to complex 4
49
Difference between complexes 1 and 2
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
50
How many protons are pumped per NADH
10
51
Is oxygen the only terminal acceptor in the ETC
No, different ones for anaerobic respiration
52
Examples of other common e acceptors
Nitrate (NO3) and sulfate (SO4 2-)
53
How is the ETC diverse
Microbe can have multiple different ETC, sometimes simultaneous Different terminal acceptors Different energy sources feed into
54
How does the ETC proton motive force generate ATP
ATP synthase
55
General overview of ATP synthase
Protons flow back along gradient, generate mechanical energy which powers ADP -> ATP
56
Parts of ATP synthase
F1 = connected to F0 through stalk F0 = protons flow through, in membrane
57
What powers addition of inorganic P to ADP
The conformational change of F1 driven by stalk rotation
58
How many H+ are pumped to produce an ATP
~3.3
59
How many ATP are produced by ETC / ATP synthase
ETC = 10 protons pumped ATP synthasev= 3.3 protons per ATP = 3 ATP per NADH
60
Summary on slide 27
ok
61
What do chemoorganotrophs do when glucose is not present
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
62
What is catabolite repression
When a better energy source (e.g. glucose) is around, enzymes using other energy sources are inhibited/not expressed
63
E. coli is a facultative anaerobe, meaning?
Can live/grow with or without O2
64
Under anaerobic conditions, e. coli respirates using
Nitrate or ferments
65
How is redox balance restored after glycolysis
Fermentation or respiration
66
How does fermentation generate ATP and redox balance
Substrate level phosphorylation Excretion of reduced fermentation products (regenerates NAD+)
67
Fermentation of glucose occurs under what conditions
Anaerobic
68
***review fermentation slides (31-37)
ok
69
Ethanol fermentation used for
Alcoholic beverages, bread
70
What can microbes ferment
Wide range of organic compounds (glucose, f.a., a.a., purines/pyrimidines)
71
Common theme of fermentation
Generate energy rich molecule than can be hydrolyzed to produce ATP, donate e to a metabolite (reduce it) and excrete it = redox balance
72
How many ATP does lactic acid fermentation generate vs how many does aerobic respiration generate
lactic acid = 2 aerobic = 38

MICRB 265 (34 decks)

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