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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is glucose stored as?

A

glycogen in liver and muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are fatty acids stored as?

A

triacylglycerol droplets in adipose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Is there a protein store?

A

No

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

When may stored energy be required

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is required to maintain glucose levels?

A

Fuel stores

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How do we survive prolonged fasting or starvation?

A

With fuel stores

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the energy equivalent in 15kg of TAG?

A

590000kJ

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What can the liver NOT use for fuel?

A

Ketones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What fuels can muscles use?

A

All fuels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What can’t the brain use for fuel?

A

Fatty acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why can’t the brain use fatty acids?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What can’t RBCs use for fuel?

A

Fatty acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why can’t RBCs use fatty acids?

A

Because they don’t have mitochondria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is adipose specialised in?

A

Storing and mobilising fats

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

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

A

No unlimited

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are excess TAGs and glucose from diet converted to?

A

stored fat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is TAG synthesis in adipocytes driven by?

A

Insulin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What things does insulin do to a adipocyte?

A
  • Promotes glucose uptake via GLUT4
  • Stimulates LPL
  • Stimulates glycolysis via hexokinase
  • Stimulates DNL
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What does glucose provide to an adipocyte?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What allows glucose uptake by adipose?

A

GLUT4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What allows glucose uptake by Liver?

A

GLUT2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Is GLUT 2 stimulated by insulin?

A

No

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Is GLUT 4 stimulated by insulin?

A

Yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is dietary fat packaged into?

A

Chylomicrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is glucose metabolised to in adipocytes?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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 conversation 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 synthase 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.