Energy Production In Carbohydrates 3 Flashcards

1
Q

What is allostery?

A

Activator/inhibitor binds at another site on enzyme

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2
Q

Metabolic pathway regulation

A

Irreversible steps can cause regulation
Reducing level of products, less substrate can get through pathways
Flux through pathways is regulated in response to need

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3
Q

Why are reversible steps not regulated?

A

Even when inhibited, reactions still come to an equilibrium so levels of product are unaffected

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4
Q

How does product inhibition work?

A

As pathway intermediates build so flux pathway will slow
Can block first enzyme in pathway, reduces entry of substrate and build up of intermediates in pathway - feedback inhibition

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5
Q

What does inhibiting the committing step do?

A

Allows substrate to be diverted into other pathways

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6
Q

Regulation of key enzymes

A

Can be inhibitory or stimulatory

E.g. catabolic pathways inhibited by high energy signals, activated by low energy signals

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7
Q

How does hormonal regulation work?

A

Hormone receptor binding
Activates signalling pathway
Protein kinase or protein phosphatase activated
Dephosphorylation/phosphorylation of target enzyme
Alters protein conformation/activity positively or negatively depending on target enzyme

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8
Q

What is feeding forward?

A

Early pathway substrate provides positive allosteric signal to stimulate a later enzyme to activate pathway

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9
Q

An example of phosphoregulation - adrenaline

A

Activates protein kinase A
Phosphorylation activates phosphorylase kinase
Phosphorylation of glycogen phosphorylase - stimulates glycogen breakdown

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10
Q

An example of phosphoregulation - insulin

A

Activates phosphatase 1
Dephosphorylaes/activates pyruvate dehydrogenase - stimulates glucose utilisation
Dephosphorylates glycogen phosphorylase

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11
Q

How does phosphofructokinase-1 regulate glycolysis?

A

Fructose-6-phosphate -> fructose-1,6-bisphosphate using phosphofructokinase-1, converting ATP to ADP
Allosteric regulation of phsophofructokinase-1 by ATP:AMP ratio

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12
Q

Allosteric regulation in muscle

A

Inhibited at high ATP

Stimulated at high AMP

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13
Q

Hormonal regulation in liver

A

Stimulated by insulin using protein phosphatase 1

Inhibited by glucagon using protein kinase A

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14
Q

What happens if there is a high NADH concentration in step 6 of glycolysis?

A

High energy levels
Causes product inhibition
Inhibition of glycolysis

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15
Q

Allosteric regulation of hexokinase by glucose-6-phosphate

A

Inhibition at step 6, high NADH=high energy level
Inhibition at step 4, PFK in response to high energy signals
Prevents metabolism of F1, 6-BP, backs up glycolytic intermediates, increased G-6-P
G-6-P negative regulator of hexokinase

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