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Semester 2-MEH > Session 2-Energy Production: Carbs > Flashcards

Session 2-Energy Production: Carbs Flashcards

1
Q

What is another name for the tricarboxylic acid cycle?

A

Krebs cycle

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2
Q

Where is pyruvate dehydrogenase (PDH) located?

A

Mitochondrial matrix

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3
Q

How many enzymes is PDH made up of?

A

5 enzymes

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4
Q

What does PDH deficiency lead to?

A

Lactic acidosis

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5
Q

What is PDH activated by? (5)

A 
Pyruvate
CoASH
NAD+
ADP
Insulin
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6
Q

What is PDH inhibited by? (4)

A

Acetyl-CoA
NADH
ATP
Citrate

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7
Q

True or false: PDH activators work by phosphorylation

A

FALSE - dephosphorylation

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8
Q

Which two reactions in the TCA cycle are irreversible?

A

1) isocitrate (C6) -> alpha-ketoglutarate (C5)

2) alpha-ketoglutarate (C5) -> succinyl-CoA (C4)

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9
Q

How many TCA cycles occur per glucose molecule?

A

2

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10
Q

How is the TCA cycle regulated?

A

Energy availability ie ATP/ADP ratio and NADH/NAD+ ratio

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11
Q

Which two enzymes are allosterically regulated by NADH and ATP in the TCA cycle?

A

1) isocitrate dehydrogenase

2) alpha-ketoglutarate dehydrogenase

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12
Q

True or false: TCA supplies biosynthetic processes

A

TRUE

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13
Q

True or false: TCA cycle is only catabolic

A

FALSE - also anabolic

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14
Q

TCA cycle is the central pathway in the catabolism of which substances? (5)

A 
Sugars
Fatty acids
Ketone bodies
AA
Alcohol
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15
Q

How is ATP produced in the TCA cycle?

A

Substrate level phosphorylation

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16
Q

True or false: TCA cycle can function in the absence of O2

A

FALSE

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17
Q

Where does electron transport and ATP synthesis occur?

A

Inner membrane of the mitochondria

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18
Q

Which coenzymes are re-oxidised in stage 4 of catabolism?

A

NADH

FADH2

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19
Q

What is O2 reduced to in stage 4 of catabolism?

A

Water

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20
Q

Why does stage 4 of catabolism occur in small steps?

A

To retain energy

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21
Q

Which two processes use reducing power to synthesise ATP?

A

1) Electron transport

2) Oxidative phosphorylation

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22
Q

What happens in electron transport?

A

Electrons on NADH and FADH2 are transferred through a series of carrier molecules to oxygen

23
Q

What happens in oxidative phosphorylation?

A

Free energy released is used to drive ATP synthesis

24
Q

True or false: the inner membrane of a mitochondrion is impermeable

A

TRUE

25
Q

What happens to electrons as they are passed from proton translocating complex (PTC) 1 to PTC3?

A

Lose energy

26
Q

In the electron transport chain, why do protons want to reenter the matrix and what prevents them from doing so?

A
  • Concentration gradient and electrical gradient

- Membrane is impermeable so can only enter through ATP synthase

27
Q

Approximately what % of energy is used to move H+ across the membrane in the electron transport chain?

A

~30%

28
Q

What is the H+ gradient across the inner mitochondrial membrane called?

A

Proton motive force (pmf)

29
Q

Where are electrons transferred to from NADH and FADH2?

A

Molecular oxygen

30
Q

Complete the sentence:

Energy from the dissipation of the pmf is coupled to the synthesis of ___ from ___

A

ATP

ADP

31
Q

True or false: electrons in FADH2 have more energy than in NADH

A

FALSE - other way round

32
Q

How many PTCs does NADH use?

A

3

33
Q

How many PTCs does FADH2 use?

A

2

34
Q

True or false: the greater the pmf, the _______ ATP is synthesised

A

More

35
Q

How is oxidative phosphorylation regulated?

A

When [ATP] is high ([ADP] is low), no substrate for ATP synthase so the inward flow of H+ stops. The concentration of H+ in the intermitochondrial space increases, preventing further H+ pumping. Electron transport is therefore stopped

36
Q

Complete the sentence:

Inhibitors ______ electron transport, preventing the acceptance of electrons by _________

A

Block

Oxygen

37
Q

Give examples of an inhibitor of oxidative phosphorylation

A

Cyanide

Carbon monoxide

38
Q

What do uncouplers of oxidative phosphorylation do?

A

Increase permeability of the inner mitochondrial membrane to protons. This dissipates the proton gradient, thereby reducing the pmf so there is no drive for ATP synthesis

39
Q

Give an example of uncouplers

A

Fatty acids

40
Q

What does the efficiency of coupling of oxidative phosphorylation depend on?

A

Tightness of coupling

41
Q

What controls the degree of coupling in brown adipose tissue and what does this allow?

A

Fatty acids

Allows extra heat generation

42
Q

What does brown adipose tissue contain that is usually inactive?

A

Thermogenin (UCP1) = naturally-occurring uncoupling protein

43
Q

What is activated in UCP1’s response to cold and noradrenaline? (2)

A

1) lipase which releases fatty acids from triacylglycerol

2) fatty acid oxidation -> NADH/FADH2 -> electron transport

44
Q

Apart from cold and noradrenaline, what else activates UCP1 and what effect does this have?

A
  • Fatty acids
  • UCP1 transports H+ back into mitochondria so electron transport is uncoupled from ATP synthesis and the energy of pmf is released as extra heat.
45
Q

In which organisms can brown adipose tissue be found in?

A

Newborn infants

Hibernating animals

46
Q

In what way are the enzymes used in oxidative phosphorylation different to those used in substrate level phosphorylation?

A

In oxidative, enzymes are membrane-associated whereas in substrate level, enzymes are soluble

47
Q

True or false: energy coupling occurs indirectly through the generation and subsequent utilisation of a proton gradient in substrate level phosphorylation

A

FALSE - ^ in oxidative

48
Q

How does energy coupling occur in substrate level phosphorylation?

A

Directly through formation of high energy hydrolysis bond

49
Q

True or false: oxidative phosphorylation can occur to a limited extent in the absence of O2

A

FALSE - ^ is substrate level

50
Q

Which is the major process for ATP synthesis?

A

Oxidative phosphorylation

51
Q

How many moles of ATP are produced per mole of glucose?

A

32

52
Q

The reaction catalysed by PDH is sensitive to the deficiency of which vitamin?

A

B1

53
Q

Which reaction does PDH catalyse?

A

Pyruvate -> acetyl-CoA + CO2

Semester 2-MEH (21 decks)

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