Energy Production In Carbohydrates 4 Flashcards

1
Q

Where does the pyruvate reaction take place?

A

Mitochondrial matrix

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2
Q

What reaction takes place in pyruvate reaction?

A

Pyruvate + CoA + NAD+ -> acetyl CoA + CO2 + NADH + H+

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3
Q

What enzyme is used in pyruvate reaction?

A

Pyruvate dehydrogenase

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4
Q

What provides the cofactors for PDH?

A

B vitamins, therefore reaction is sensitive to vitamin B1 deficiency

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5
Q

Is the pyruvate reaction reversible?

A

Reaction is irreversible

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6
Q

What can inhibit the pyruvate reaction?

A

Acetyl CoA
NADH
ATP
Citrate

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7
Q

What can activate the pyruvate reaction?

A

CoASH
NAD+
ADP
Insulin

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8
Q

What can a PDH deficiency result in?

A

Lactic acidosis

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9
Q

Where does the Krebs cycle take place?

A

Mitochondria

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10
Q

What happens in the Krebs cycle?

A

Acetyl is converted to 2CO2
Oxidative as requires NAD+ and FAD
Some energy is produced as ATP/GTP

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11
Q

What is produced in the Krebs cycle for every glucose molecule?

A

Krebs cycle occurs twice for each glucose molecule
6 NADH
2 FADH2
2 GTP

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12
Q

How is the Krebs cycle regulated in general?

A

Regulated by energy availability (ATP/ADP ratio, NADH/NAD+ ratio)

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13
Q

How is the Krebs cycle regulated at isocitrate to C5?

A

Isocitrate dehydrogenase enzyme used

Stimulated by ADP, inhibited by NADH and ATP

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14
Q

How is the Krebs cycle regulated at alpha-ketoglutarate (C5) to succinyl-CoA (C4)?

A

Alpha-ketoglutarate dehydrogenase enzyme used

Inhibited by NADH, ATP and succinyl-CoA

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15
Q

What is the Krebs cycle a central pathway for?

A

Catabolism of sugars, fatty acids, ketone bodies, amino acids and alcohol

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16
Q

Can the Krebs cycle occur in the absence of O2?

A

No, cannot function

17
Q

Electron transport

A

Inner mitochondrial membrane highly impermeable
Electrons transferred through series of carrier molecules to O2, with release of energy
Some energy lost as heat
H+ gradient across inner mitochondrial membrane = proton motive force

18
Q

What is the equation for proton translocating ATPase (ATP synthase)?

A

ATP + 2H+ ADP + Pi + 2H+
LHS is in mitochondrial matrix, RHS is in cytoplasm
2 H+ travel from mitochondrial matrix across inner membrane to intermembrane space

19
Q

What happens in ATP synthesis?

A

Return of H+ is favoured energetically by electrochemical gradient
H+ can only return across membrane via ATP synthase which drives ATP synthesis

20
Q

What is oxidative phosphorylation?

A

Electron transport coupled to ATP synthesis
Electrons are transferred from NADH and FADH2 to molecular oxygen
Energy released used to generate proton gradient
Energy from dissipation of proton motive force is coupled to synthesis of ATP from ADP

21
Q

How is oxidative phosphorylation regulated?

A

Regulated by mitochondrial [ATP]
When [ATP] high, [ADP] low, no substrate for ATP synthase
Therefore inward flow of H+ stops
Conc of H+ in intermitochondrial space increases
Prevents further H+ pumping, stops electron transport
Reverses with low [ATP]

22
Q

Inhibition of oxidative phosphorylation

A

Inhibitors block electron transport

E.g. cyanide prevents acceptance of electrons by O2 as it binds more tightly than O2

23
Q

Uncoupling of oxidative phosphorylation

A

Uncoupled increase permeability of mitochondrial inner membrane to protons
Dissipate proton gradient, reduces proton motive force
No drive for ATP synthesis

24
Q

Efficiency of coupling of oxidative phosphorylation

A

Rest of energy lost as heat
Efficiency depends on tightness of coupling
Can be varied in some tissues

25
Q

Brown adipose tissue

A

Allows extra heat generation
Contains thermogenin (UCP1)
In response to cold, noradrenaline activates many processes including lipase to release fatty acids from triacylglycerol
Electron transport uncoupled from ATP synthesis, energy is released as extra heat
Found in newborn infants