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Phase 1 - S2 Metabolism, Endocrinology, Haematology > TCA And Oxidative Phosphorylation > Flashcards

TCA And Oxidative Phosphorylation Flashcards

1
Q

What does Pyruvate Dehydrogenase do?

A

Catalyses the conversion of pyruvate to acetyl CoA, producing CO2 and NADH

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2
Q

Where is Pyruvate Dehydrogenase found

A

Mitochondrial matrix

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3
Q

Why is Pyruvate Dehydrogenase sensitivity to a vitamin B1 deficiency

A

The enzyme activity requires cofactors and B vitamins provide these factors

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4
Q

True or false: the reaction catalysed by pyruvate dehydrogenase is reversible

A

False. It’s irreversible making it a key regulatory step

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5
Q

What activates pyruvate dehydrogenase

A

Pyruvate, CoA, NAD+, ADP and Insulin (low energy signals)

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6
Q

What inhibits Pyruvate Dehydrogenase

A

Acetyl CoA, NADH, ATP, citrate (high energy signals)

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7
Q

True or False: Pyruvate cannot be formed from acetyl-CoA

A

True, the loss of CO2 is irreversible

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8
Q

What does a deficiency in pyruvate dehydrogenase lead to

A

Lactic acidosis (increase in blood lactate levels)

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9
Q

Where does the TCA cycle occur

A

Mitochondrial matrix

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10
Q

What does TCA stand for

A

Tricarboxylic Acid cycle

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11
Q

Outline the Kreb’s cycle

A
  • Acetyl CoA binds with the 4 carbon oxaloacetate to form the 6 carbon citrate
  • citrate is converted into the 6 carbon isocitrate
  • isocitrate dehydrogenase oxidises isocitrate causing the loss of CO2 and production of NADH
  • alpha-ketoglutarate is oxidised by alpha-ketoglutarate dehydrogenase causing the loss of CO2 and production of NADH
  • compound is modified releasing CoA and producing GTP
  • FADH2 is produced
    NADH produced to reform oxaloactetate
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12
Q

For 1 molecule of glucose what is produced in the TCA cycle

A

6 NADH
2 FADH2
2 GTP

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13
Q

What are isocitrate dehydrogenase and alpha-ketoglutarate dehydrogenase regulated by

A

High energy signals (ATP and NADH)

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14
Q

True of false: alpha-ketoglutarate dehydrogenase is inhibited by its product

A

True

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15
Q

How does the Kreb’s cycle allow for anabolic reactions

A

It supplies intermediates for biosynthetic processes

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16
Q

Give some example of interconversions allowed by the Kreb’s cycle

A
  • citrate to fatty acids
  • alpha-ketoglutarate into amino acids
  • oxaloacetate into glucose and amino acids
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17
Q

Does the Kreb’s cycle occur in the absence of oxygen

A

No, as the NADH and FADH2 cant offload their hydrogen and so there are no free NAD+ and FAD to pick up hydrogen so the TCA stops

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18
Q

By the end of the Kreb’s cycle how much ATP has been produced per glucose

A

4 ATP

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19
Q

Where does oxidative phosphorylation occur

A

Inner mitochondrial membrane

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20
Q

What happens to NADH and FADH2 in oxidative phosphorylation

A

They are reoxidised

21
Q

Outline the electron transport which occurs before oxidative phosphorylation

A

NADH and FADH2 offload their electrons through a series of protein translocating complexes. As the electrons are transferred through the chain to oxygen they release energy which move hydrogen across the membrane

22
Q

Energy from what allows the Hydrogen ions to pass into the intermitochondrial space

A

Energy is released when the electrons are transferred through the protein carrier molecules

23
Q

Why are the electrons transferred through more than one carrier molecule in steps

A

So that energy is contained and you have more control on the production so less energy is wasted

24
Q

How many hydrogen ions travel through the membrane due to 1 molecule of NADH offloading it’s electron pair

A

6

25
Q

How many hydrogen ions are transferred through the carrier molecules when 1 molecule of FADH2 offloads it’s electron pair

A

4

26
Q

Why does NADH allow to movement of more hydrogen ions

A

It’s a higher energy molecule

27
Q

What proportion of the energy released by the movement of electrons is used to pump hydrogen ions across the membrane

A

30% the rest is lost as heat

28
Q

Why is a hydrogen ion gradient allowed to build up

A

The inner mitochondrial membrane is very impermeable so hydrogen ions can move through easily, they had to move through the carrier molecules

29
Q

What is the proton motive force

A

The hydrogen ion gradient across the inner mitochondrial membrane

30
Q

What does ATP synthase catalyse

A

The production of ATP from ADP + Pi as hydrogen ions flow through the enzymes down their electrochemical gradient

31
Q

How many protein translocation complexes do NADH and FADH2 use

A

NADH -3

FADH2 -2

32
Q

What happens if the proton motive force is increased

A

More ATP is synthesised

33
Q

Oxidation of 2 moles of NADH and FADH2 produce how many moles of ATP

A

NADH- 5

FADH2 - 3

34
Q

What happens to oxidative phosphorylation if ATP concentration is high

A

There is a low ADP concentration so there’s no substrate for ATP synthase so the inward flow of hydrogen ions stops and the H+ conc in the intermitochondrial space increases stopping the electron transport chain

35
Q

What regulates electron transport and oxidative phophorylation

A

ATP concentrations

36
Q

What does an inhibitor of oxidative phosphorylation do

A

Blocks the electron transport by preventing the acceptance of electrons by oxygen

37
Q

Give an example of an oxidative phosphorylation inhibitor

A

Cyanide and carbon monoxide

38
Q

What are uncouplers

A

Molecules that increase the permeability of the inner mitochondrial membrane to protons so dissipate the proton gradients reducing the proton motive force so there’s no drive for ATP synthesis

39
Q

Give 3 examples of uncouplers

A

Fatty acids, dinitrophenol and dinitrocresol

40
Q

What are oxidative phosphorylation diseases

A

Genetic defects in proteins encoded by mtDNA which lead to a decrease in electron transport and ATP synthesis

41
Q

What naturally occurring uncoupling protein does brown adipose tissue contain

A

Thermogenin

42
Q

How does brown adipose tissue produce extra heat

A

In response to the cold and noradrenaline lipase releases fatty acids from triacylglycerol and then go on to activate thermogenin (or is oxidised).

43
Q

What does thermogenin do?

A

Transports H+ back into the mitochondria so the energy from the proton motive force is released as extra heat

44
Q

What mechanism of ATP production is the major process in cells requiring large amounts of energy

A

Oxidative phosphorylation

45
Q

Which mechanism for ATP production can occur in the absence of oxygen (to some extent)

A

Substrate level phosphorylation

46
Q

How does energy coupling occur in substrate level phosphorylation

A

Directly through the formation of high energy from hydrolysis bonds (phosphoryl group transfer)

47
Q

How does energy coupling occur in oxidative phosphorylation

A

Energy coupling occurs indirectly through generating and using the proton motive force

48
Q

Where does substrate level phosphorylation take place

A

In the cytoplasm and mitochondrial matrix

49
Q

What is the net yield of ATP from 1 molecule of glucose following the Kreb’s cycle (taking into account the NADH and FADH produced)

A

32

Phase 1 - S2 Metabolism, Endocrinology, Haematology (22 decks)

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