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BIOC192 2024 > Lecture 32 - Coordinating Metabolism: Fuel Storage > Flashcards

Lecture 32 - Coordinating Metabolism: Fuel Storage Flashcards

1
Q

Why do we need fuel stores?

A

Because we can’t store ATP or transfer it to other tissues, it must be made in the cell requiring it at the time by oxidizing fuels

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2
Q

What is glucose stored as?

A

glycogen in liver and muscle

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3
Q

What are fatty acids stored as?

A

triacylglycerol droplets in adipose

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4
Q

Is there a protein store?

A

No

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5
Q

When may stored energy be required

A

between meals, overnight, for activity i.e. exercise

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6
Q

What is required to maintain glucose levels?

A

Fuel stores

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7
Q

How do we survive prolonged fasting or starvation?

A

With fuel stores

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8
Q

What is the energy equivalent in 15kg of TAG?

A

590000kJ

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9
Q

What can the liver NOT use for fuel?

A

Ketones

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10
Q

What fuels can muscles use?

A

All fuels

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11
Q

What can’t the brain use for fuel?

A

Fatty acids

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12
Q

Why can’t the brain use fatty acids?

A

They can’t cross the blood brain barrier (BBB)

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13
Q

What can’t RBCs use for fuel?

A

Fatty acids

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14
Q

Why can’t RBCs use fatty acids?

A

Because they don’t have mitochondria

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15
Q

What is adipose specialised in?

A

Storing and mobilising fats

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16
Q

Is there a limit on the amount of fat you store?

A

No unlimited

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17
Q

What are excess TAGs and glucose from diet converted to?

A

stored fat

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18
Q

What is TAG synthesis in adipocytes driven by?

A

Insulin

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19
Q

What things does insulin do to a adipocyte?

A
  • Promotes glucose uptake via GLUT4
  • Stimulates LPL
  • Stimulates glycolysis via hexokinase
  • Stimulates DNL
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20
Q

What does glucose provide to an adipocyte?

A

Glycerol-phosphate backbone, and provides acetyl-CoA for de novo lipogenesis (DNL)

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21
Q

What allows glucose uptake by adipose?

A

GLUT4

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22
Q

What allows glucose uptake by Liver?

A

GLUT2

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23
Q

Is GLUT 2 stimulated by insulin?

A

No

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24
Q

Is GLUT 4 stimulated by insulin?

A

Yes

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25
Q

What is dietary fat packaged into?

A

Chylomicrons

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26
Q

What is glucose metabolised to in adipocytes?

A

Glycerol-3-Phosphate, and then used as the backbone for TAG synthesis

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27
Q

What does stimulation of lipoprotein lipase (LPL) by insulin do?

A

hydrolyses TAGs to release FA into tissues where they are resynthesized into TAGs

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28
Q

What happens when glucose undergoes glycolysis in the liver?

A

Glucose undergoes glycolysis generating excess acetyl-CoA that can be synthesised into FAs via the FA synthase complex, then into TAGs, and packaged into VLDL particles

29
Q

How is excess glucose carbon converted to fatty acids?

A

Via acetyl CoA

30
Q

Where does the conversion of Glucose to Fatty acids take place?

A

Mainly in the liver but also in adipose

31
Q

Does it require energy to convert Glucose to fatty acids

A

Yes

32
Q

How are fatty acids exported?

A

As TAGS in VLDL

33
Q

How are fatty acids delivered to adipose?

A

Via LPL activity and stored as TAGs

34
Q

What overall stimulates the conversion of glucose to fatty acids?

A

Insulin

35
Q

What is glycogen?

A

A branched polysaccharide

36
Q

Where is glycogen stored ?

A

In the liver and muscle

37
Q

Where may you find glycogen in the cell?

A

As granules in the cytoplasm

38
Q

What type of bonds are in glycogen?

A

1-4 and,1-6 glycosidic bonds

39
Q

What happens during glycogen synthesis?

A

Glucose is trapped in cell, and diverts from glycolysis

40
Q

What is the starting substrate in the glycogen synthase reaction?

A

UDP-Glucose (UDP-G).

41
Q

What happens to UDP in the glycogen synthase reaction?

A

It is released from UDP-Glucose, leaving the glucose unit to attach to the glycogen chain.

42
Q

What intermediate is formed during the glycogen synthase reaction?

A

Oxonium ion intermediate.

43
Q

What bond is formed when a glucose unit is added to glycogen?

A

A new glycosidic bond (α(1→4)).

44
Q

What is the enzyme responsible for catalyzing the glycogen synthesis reaction?

A

Glycogen synthase.

45
Q

What happens to the glycogen chain after the reaction?

A

It grows by one glucose unit, forming glycogen with “n+1 residues.”

46
Q

What is released during the formation of the glycosidic bond?

A

A hydrogen ion (H+).

47
Q

What does stimulation of the insulin signalling pathway activate?

A

PKB (aka AKT), also activate a phosphatase (PP1)

48
Q

WHat does PKB activation do?

A

Inactivates glycogen synthase kinase (GSK3)

49
Q

What does GSK3 inactivation do?

A

Prevents glycogen synthase from being phosphorylated which keeps it active

50
Q

What does activation of phosphatase (PP1) do?

A

Dephosphorylates glycogen synthase which also helps to keep it active

51
Q

What enzyme is responsible for introducing branches in glycogen?

A

Branching enzyme.

52
Q

What happens to the glycogen chain after branching occurs?

A

Both branching chains can grow

53
Q

When and where does glycogen synthesis occur?

A

In liver and muscle immediately after a meal

54
Q

What energy inputs does glycogen synthesis require?

A

ATP and UTP

55
Q

What stimulates glycogen synthesis?

A

Insulin

56
Q

What enzymes are required for Glycogen synthesis?

A

Glycogen synthase, and branching enzyme

57
Q

What is the high energy precursor that glycogen is made from?

A

UDP-Glucose

58
Q

What happens to excess glucose that isn’t converted to glycogen?

A

Converted to acetyl-CoA and then into fatty acids by the FA synthase complex in liver

59
Q

What is liver glycogen important for?

A

Maintaining blood glucose levels

60
Q

How big are glycogen granules?

A

0.1 µm

61
Q

How big are mitochondria?

A

10 µm

62
Q

Where can muscle glycogen be used?

A

Only within muscle

63
Q

Why can muscle glycogen only be used within muscle?

A

Muscle cells are missing glucose-6 phosphotase

64
Q

What can help enhance glycogen stores?

A

Carb loading

65
Q

What benefits does carb loading have?

A
  • Has been shown to be beneficial for endurance athletes
  • Prolongs time to fatigue and protects against exercise-induced hypoglycaemia
66
Q

What are glycogen storage diseases?

A

Inherited metabolic disorders involving a deficiency of one of the enzymes responsible for glycogen synthesis or breakdown

67
Q

What can a glycogen storage disease lead to?

A

an abnormal accumulation or deficiency of glycogen in liver or muscles

68
Q

What are some potential symptoms from glycogen storage diseases

A

hypoglycemia, ketosis, muscle cramps and fatigue,
enlarged liver (hepatomegaly), growth retardation in children.

BIOC192 2024 (35 decks)

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