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Nutrition and Energy > 6. Glycolysis and Gluconeogenesis > Flashcards

6. Glycolysis and Gluconeogenesis Flashcards

1
Q

Where does NAD regeneration take place when conditions are anaerobic?

A

Mitochondria

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2
Q

NAD cannot pass the MM usually; how has it evolved to move between the MM and cytosol?

A

Glycerinophosphate shuttle

Malate-Aspartate shuttle

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3
Q

Explain the GP shuttle

A

NAD maintains glycolysis in cytosol
Dihydroxyacetonphosphate forms glycerin-3-phosphate
G-3-P enters mitochondria
G-3P reforms Dihydroxyacetonphosphate
Coenzyme FAD is reduced in this reaction
Dihydroxyacetonphosphate returns to cytosol

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4
Q

Explain the M-A shuttle

A 
OAA -> Malate
Malate into mitochondria
Malat -> OAA
NAD reduced
OAA -> Aspartate
Aspartate back into cytosol
Aspartate -> OAA
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5
Q

Explain NAD regeneration in anaerobic conditions

A

Reduced NAD during glycolysis formed when glyceraldehyde-3-phosphate -> 1,3-biphosphoglycerate

NAD reformed when pyruvate -> lactate

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6
Q

What is the fate of lactate?

A

Reforms pyruvate when oxygen becomes plentiful again

Forms glucose via gluconeogenesis in muscles

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7
Q

How long can the body survive without food?

A

30-40 days

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8
Q

Why is gluconeogensis important for erythrocytes and the brain?

A

Both have absolute glucose requirements

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9
Q

What level must BG be maintained at?

A

4-8mM

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10
Q

What is gluconeogenesis?

A

Formation of glucose from non-carbohydrates

Occurs in the liver, mainly

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11
Q

What is glycolysis?

A

Energy capture in the form of ATP and NADH from conversion of glucose into pyruvate

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12
Q

Substrates for gluconeogenesis

A 
Pyruvate
Lactate 
Amino Acids (only leucine and lysine are non-gluconeogenic)
Glycerol
OAA
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13
Q

Explain gluconeogenesis from fatty acids

A

Cannot occur from FFA

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14
Q

Explain gluconeogenesis from triglycerides

A

TG -> 3FFA + Glycerol

Glycerol -> Glyceraldehyde-3-phosphate -> fructose-1,6-bisphosphate

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15
Q

Explain the relationship between glycolysis and gluconeogenesis

A

Gluconeogensis is glycolysis in reverse apart from the three irreversible steps

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16
Q

How much ATP does gluconeogenesis require?

A

6

17
Q

Where are the ATP for gluconeogenesis obtained from?

A

Pyruvate carboxylase
PEP carboxykinase
Phosphoglycerate kinase

18
Q

How many NADH molecules does glyceraldehyde DH consume?

A

2

19
Q

Relationship between AMP and ATP

A

At high energy levels: ATP high, AMP low

20
Q

When does AMP stimulate glycolysis produce ATP?

A

Low energy levels

21
Q

What does AMP inhibit and why?

A

Gluconeogenesis; to prevent futile cycles and conserve energy

22
Q

How is glycolysis inhibited?

A

ATP at high energy levels

23
Q

What intermediates stimulate gluconeogenesis?

A

Citrate and Acetyl CoA

24
Q

Fructose-2,6-Bisphosphate is a regulatory molecule. How is it synthesised and subsequently broken down?

A

Synthesised by PFK2 from F-6-P

Broken down by FBPase2

25
Q

Explain the effects of Fructose-2,6-Bisphosphate on glycolysis and gluconeogenesis

A

Stimulates glycolysis

Inhibits gluconeogenesis

26
Q

Explain the effects of insulin on Fructose-2,6-Bisphosphate

A

Inhibits FBPase2, activates PFK2;

Raises F-2,6-BP levels

27
Q

Explain the effects of glucagon on Fructose-2,6-Bisphosphate

A

Inhibits PFK2, activates FBPase2;

Lowers F-2,6-BP

28
Q

How can lactate form glucose and what is this particular process known as?

A

Passed from an organ to the liver via blood to be used in gluconeogenesis - the Cori Cycle

29
Q

When do muscles produce alanine?

A

Anaerobic conditions by combining amino acids with pyruvate

30
Q

How does alanine lead to production of glucose? Where does it occur and why?

A

The alanine cycle - similar to Cori’s

Skeletal muscle; to eliminate nitrogen while replenishing the energy supply for muscle during starvation

31
Q

Which cycle is more productive out of Alanine and Cori cycle?

A

Cori

Nutrition and Energy (19 decks)

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