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Module 104 - Nutrition, metabolism & excretion > T2 L8 Regulation of carbohydrate metabolism > Flashcards

T2 L8 Regulation of carbohydrate metabolism Flashcards

1
Q

What does glycolysis produce?

A

Energy in the form of ATP by substrate level & oxidative phosphorylation
Glycerol-3-phosphate for fat synthesis
Acetyl CoA for fat & cholesterol synthesis
Amino acids

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2
Q

What does PFK-1 do?

A

Phosphofructokinase 1 catalyses the first step in glycolysis

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3
Q

What are some non-carbohydrate precursors that are used for de novo glucose synthesis?

A

Lactate from glycolysis
Amino acids from protein breakdown
Glycerol from fat metabolism (not fatty acids)

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4
Q

Where does gluconeogenesis occur?

A

Liver

Kidneys

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5
Q

What is the function of gluconeogenesis?

A

Maintains blood glucose during fasting, starvation or when glycogen reserves are depleted to preserve glucose-dependent cerebral function & red blood cell metabolism

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6
Q

What are some enzymes that regulate gluconeogenesis?

A

Pyruvate carboxylase
Phosphoenolpyruvate carboxykinase
Fructose-1,6-bisphosphate
Glucose-6-phosphatase

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7
Q

What does gluconeogenesis require?

A

Energy from the metabolism of fatty acids released from adipose tissue
Carbon skeletons from lactate, amino acids or glycerol released from triglycerides by lipolysis in adipose tissue

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8
Q

What does ATP do to glycolysis?

A

It inhibits glycolysis
Sign of high energy levels in the muscle
Prevents glucose being used by glycolysis when ATP is available
Co-ordinates glycolysis with glycogen breakdown via phosphorylase

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9
Q

What does AMP do to glycolysis?

A

It is present when ATP is depleted such as during muscle contraction or anoxia
Competes with ATP
Increases glycolysis & energy production
Co-ordinates glycolysis with glycogen breakdown via phosphorylase

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10
Q

What converts Fru-6-PO4 to Fru-1,6-(PO4)2?

A

6-phosphofructose-1-kinase

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11
Q

What converts Fru-1,6- (PO4)2 to Fru-6-PO4?

A

Fructose-1,6-bisphosphate

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12
Q

Why does H+ increase during anoxia or anaerobic muscle contraction?

A

Due to lactic acid production

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13
Q

What does H+ do to PFK-1?

A

It regulates it
H+ inhibit glycolysis to prevent cellular pH falling too low & damaging cellular machinery
In the heart H+ can be overcome by a high AMP which leads to cellular damage & chest pains experienced in heart attacks & angina

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14
Q

How can PFK-1 be regulated?

A

H+ ions

Nutrients such as fructose-6-phosphate, fructose-2,6-bisphosphate, citrate

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15
Q

What does fructose-6-phosphate do to PFK-1?

A

It activates it
Sign of high rate of glucose entry or glycogen breakdown
Stimulates glycolysis to allow utilisation for energy production or fat synthesis

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16
Q

What does fructose-2,6-bisphosphate do to PFK-1?

A

Activates it
Sign of high rate of glucose entry or glycogen breakdown
Most potent allosteric activator known
Stimulates glycolysis to allow utilisation for energy production or fat synthesis

17
Q

What does citrate do to PFK-1?

A

It inhibits it
Signals TCA cycle overload - more acetyl CoA than can be oxidised
Or signals fatty acid oxidation & the need to conserve glucose by inhibiting glycolysis

18
Q

What does F-6-P do to fructose-2,6-bisphosphate?

A 
It activates it
Increase in glucose concentration
Increase in glycogen breakdown in the muscle
AMP - increased contraction
Glycolysis is activated
19
Q

What does citrate do to fructose-2,6-bisphosphate?

A

Inhibits it
Increased fatty acid oxidation - TCA cycle overload
Glycolysis is inhibited

20
Q

How is glycolysis inhibited?

A

Presence of sufficient energy ATP
Fatty acid oxidation
H+ ions - lots of lactate present

21
Q

How is glycolysis activated?

A

Low levels of energy - AMP

Lots of glucose or its metabolites

22
Q

How is gluconeogenesis stimulated in the short term?

A

Glucagon & adrenaline by changes in protein phosphorylation or mobilisation of fatty acids & production of acetyl CoA

23
Q

How is gluconeogenesis stimulated in the long term?

A

Occurs through enzyme induction by glucagon, glucocorticoids & thyroid hormones

24
Q

How is gluconeogenesis acutely inhibited?

A

By insulin via dephospho rylation & suppression of lipolysis

25
Q

How is gluconeogenesis inhibits in the long term?

A

Suppression of gluconeogenic enzymes

26
Q

What is the equation for the conversion of ammonia to urea?

A

NH3 + CO2 + 2H2O + 3ATP + aspartate –> urea + fumarate + 2ADP + AMP + 2Pi + PPi

27
Q

Where is fumarate converted to oxaloacetate?

A

In the cytoplasm

Generates substrate for gluconeogenesis

28
Q

How is glycolysis regulated?

A

At the level of glucose transport into the cell, PFK-1 & pyruvate kinase

Module 104 - Nutrition, metabolism & excretion (31 decks)

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