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BGM1002-Biochemistry > BGM1002/L24 Gluconeogenesis > Flashcards

BGM1002/L24 Gluconeogenesis Flashcards

1
Q

What are normal blood glucose levels?

A

4-6mmol/L

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2
Q

What 2 hormones are involved in blood glucose homeostasis?

A

Insulin and glucagon

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3
Q

Why must blood glucose levels be regulated? (3)

A

Glucose is preferred energy source of brain and CNS
Only fuel source of RBC
Breakdown in blood glucose homeostasis causes problems

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4
Q

What is the only fuel source of RBCs?

A

Glucose

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5
Q

Define blood glucose homeostasis.

A

Maintenance of blood sugar levels within narrow physiological limits

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6
Q

What percentage of glucose does the brain use?

A

75% or 120g

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7
Q

How much glucose is circulating the body at a given time?

A

20g

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8
Q

How much glucose is readily available as glycogen at any given time?

A

190g

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9
Q

How long would stored glucose last in the body?

A

1 day

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10
Q

When does hypoglycaemia occur? (3)

A

Starvation
Insulin overdose
During and after exercise

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11
Q

What results from hyperglycaemia? (3)

A

Low glucose levels inside cells
Hyperosmolar hyperglycaemic state
Long-term complications

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12
Q

When does hyperglycaemia occur? (2)

A

Post-prandial (meal)
Inadequate insulin administration

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13
Q

When is gluconeogenesis initiated?

A

2 hours post-prandially

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14
Q

Give an advantage of gluconeogenesis.

A

Preserves glycogen for emergencies

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15
Q

What is the maximum period that gluconeogenesis occurs for?

A

8-12 hours

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16
Q

Where does gluconeogenesis occur?

A

High-intensity exercise principally in liver

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17
Q

Name 3 sources for gluconeogenesis.

A

Pyruvate/lactate
Glycerol
Citric acid cycle intermediates
Amino acids

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18
Q

When is lactate produced in cells? (2)

A

When pyruvate is not needed for Krebs cycle
When pyruvate cannot be fed into the cycle due to lack of oxygen

19
Q

What organ is responsible for most lactate production?

A

Skeletal muscle

20
Q

Why must lactate be transported to the liver?

A

It cannot be used for anything else
It is converted to glucose to be (re)used

21
Q

What can pyruvate be converted into in skeletal muscle?

A

Alanine

22
Q

How many pyruvate molecules are used to create a glucose molecule?

A

2

23
Q

Name 3 energy unfavourable reactions in glycolysis that must be overcome in gluconeogenesis.

A

Pyruvate -> PEP
F-1,6-bisphosphate -> F-6-P
G-6-P -> Glucose

24
Q

What is step 1 in gluconeogenesis?

A

Pyruvate -> phosphoenolpyruvate

25
Q

Name the intermediates in step 1 of gluconeogenesis.

A

Pyruvate -> oxaloacetate
Oxaloacetate -> malate

26
Q

What enzyme converts pyruvate to oxaloacetate?

A

Pyruvate carboxylase

27
Q

What enzyme converts oxaloacetate to PEP?

A

PEP carboxykinase

28
Q

Why must oxaloacetate be converted to malate in step 1 of gluconeogenesis?

A

To exit mitochondria

29
Q

Name any additional molecules required to convert pyruvate to oxaloacetate.

A

CO2 + Biotin + ATP -> Biotin + ADP + Pi

30
Q

Name any additional molecules required to convert oxaloacetate to PEP.

A

GTP -> GDP + CO2

31
Q

What is step 2 of gluconeogenesis?

A

Fructose-1,6-bisphosphate -> Fructose-6-phosphate

32
Q

What enzyme is required to convert F-1,6-phosphate to F-6-phosphate?

A

Fructose-1,6-bisphosphatase

33
Q

What additional molecules are required in step 2 of gluconeogenesis?

A

H2O -> Pi

34
Q

Name step 3 of gluconeogenesis.

A

Glucose-6-phosphate -> glucose

35
Q

What enzyme is required for step 3 of gluconeogenesis?

A

Glucose-6-phosphatase

36
Q

What additional molecules are required for step 3 of gluconeogenesis?

A

H2O -> Pi

37
Q

What is the net cost of gluconeogenesis in the form of ATP and GTP?

A

4ATP and 2 GTP

38
Q

Where does the ATP for gluconeogenesis come from?

A

Lipid oxidation
Amino acid catabolism

39
Q

What are the effects of overexpression of phosphoenolpyruvate carboxykinase in mice?

A

Enhanced exercise capacity (6k vs 0.2k)
Ate 60% more than controls
1/2 body weight and 10% body fat of controls
Increased mitochondria
High triglyceride concentration
Extended lifespan (+2yrs)

40
Q

What are the effects of a high-protein, carbohydrate-free diet in humans?

A

42% increase in energy expenditure
Body uses amino acids as pre-cursors for gluconeogenesis

41
Q

How is gluconeogenesis regulated?

A

Allosterically of enzymes for irreversible steps in the liver

42
Q

When is gluconeogenesis activated?

A

When cells have a surplus of energy

43
Q

Why do AMP and ADP inhibit gluconeogenesis?

A

Low energy status
Need to send pyruvate into TCA cycle to get energy

44
Q

Why do citrate and acetyl CoA activate gluconeogenesis?

A

Indicate high energy status
Plenty of biosynthetic precursors
Favours converstion of pyruvate into G6P for glycogen synthesis

BGM1002-Biochemistry (29 decks)

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