Metabolic pathways: gluconeogenesis Flashcards

1
Q

When does gluconeogenesis occur?

A

During prolonged starvation

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2
Q

What is gluconeogenesis?

A

Synthesis of glucose

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3
Q

What are the precursors of gluconeogenesis?

A

Lactate- synthesised by skeletal muscle

Amino acids- derived from muscle protein by proteolysis

Glycerol- derived from triglycerides by lipolysis in adipose tissue

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4
Q

Where does energy come from?

A

Oxidation of fatty acids released from adipose tissue

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5
Q

Where does gluconeogenesis occur?

A

Liver, small amount in the kidney

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6
Q

What are the three irreversible reactions in glycolysis?

A

the 1st, 3rd last reaction

Catalysed by
Hexokinase
Phosphofructokinase
Pyruvate kinase

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7
Q

What is requires for gluconeogenesis?

A

Additional enzymes to bypass irreversible stages

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8
Q

How many enzymes are required to bypass irreversible reactions?

A

4 liver enzymes

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9
Q

What does glucogenogenesis proceed via?

A

The synthesis of oxaloacetate in mitochondria

  • the TCA cycle intermediate which accepts acetyl groups
  • important for accepting acetyl groups for fat breakdown
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10
Q

How many pyruvate are needed to make a glucose molecule?

A

2

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11
Q

What is important about glugoneogenesis ?

A

Very energy expensive

  • 4ATP
  • 2GTP are consumed to make one glucose
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12
Q

Where does lactate come from?

A

Formed in fast-twitch muscle under conditions of heavy exercise

Blood transports lactate to liver

Converted back to pyruvate

Costs 6ATP to form glucose

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13
Q

What is the significance of lactate as a precursor?

A

Allows muscle to continue for at least a while

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14
Q

What are the two groups of amino acids?

A

Keto-genic = cannot be used for making glucose

Glucogenic= can be used for making glucose

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15
Q

What happens if gluconeogenesis removes oxaloacetate?

A

The TCA cycle cannot acept further acetyl groups

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16
Q

How is gluconeogenesis regulated?

A

System level by hormones
>glucagon
>insulin

At the level of individual cells

17
Q

How is glycolysis and glucomeogenesis regulated at cellular level?

A

High AMP or ADP means low energy

High ATP means high energy

Fructose 2,6-bisphosphate
>high in fed state
>low in starved state

Citric acid, alanine, acetyl CoA
-high when intermediates or building blocks are abundant