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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
What is dietary fat packaged into?
Chylomicrons
26
What is glucose metabolised to in adipocytes?
Glycerol-3-Phosphate, and then used as the backbone for TAG synthesis
27
What does stimulation of lipoprotein lipase (LPL) by insulin do?
hydrolyses TAGs to release FA into tissues where they are resynthesized into TAGs
28
What happens when glucose undergoes glycolysis in the liver?
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
How is excess glucose carbon converted to fatty acids?
Via acetyl CoA
30
Where does the conversion of Glucose to Fatty acids take place?
Mainly in the liver but also in adipose
31
Does it require energy to convert Glucose to fatty acids
Yes
32
How are fatty acids exported?
As TAGS in VLDL
33
How are fatty acids delivered to adipose?
Via LPL activity and stored as TAGs
34
What overall stimulates the conversion of glucose to fatty acids?
Insulin
35
What is glycogen?
A branched polysaccharide
36
Where is glycogen stored ?
In the liver and muscle
37
Where may you find glycogen in the cell?
As granules in the cytoplasm
38
What type of bonds are in glycogen?
1-4 and,1-6 glycosidic bonds
39
What happens during glycogen synthesis?
Glucose is trapped in cell, and diverts from glycolysis
40
What is the starting substrate in the glycogen synthase reaction?
UDP-Glucose (UDP-G).
41
What happens to UDP in the glycogen synthase reaction?
It is released from UDP-Glucose, leaving the glucose unit to attach to the glycogen chain.
42
What intermediate is formed during the glycogen synthase reaction?
Oxonium ion intermediate.
43
What bond is formed when a glucose unit is added to glycogen?
A new glycosidic bond (α(1→4)).
44
What is the enzyme responsible for catalyzing the glycogen synthesis reaction?
Glycogen synthase.
45
What happens to the glycogen chain after the reaction?
It grows by one glucose unit, forming glycogen with "n+1 residues."
46
What is released during the formation of the glycosidic bond?
A hydrogen ion (H+).
47
What does stimulation of the insulin signalling pathway activate?
PKB (aka AKT), also activate a phosphatase (PP1)
48
WHat does PKB activation do?
Inactivates glycogen synthase kinase (GSK3)
49
What does GSK3 inactivation do?
Prevents glycogen synthase from being phosphorylated which keeps it active
50
What does activation of phosphatase (PP1) do?
Dephosphorylates glycogen synthase which also helps to keep it active
51
What enzyme is responsible for introducing branches in glycogen?
Branching enzyme.
52
What happens to the glycogen chain after branching occurs?
Both branching chains can grow
53
When and where does glycogen synthesis occur?
In liver and muscle immediately after a meal
54
What energy inputs does glycogen synthesis require?
ATP and UTP
55
What stimulates glycogen synthesis?
Insulin
56
What enzymes are required for Glycogen synthesis?
Glycogen synthase, and branching enzyme
57
What is the high energy precursor that glycogen is made from?
UDP-Glucose
58
What happens to excess glucose that isn't converted to glycogen?
Converted to acetyl-CoA and then into fatty acids by the FA synthase complex in liver
59
What is liver glycogen important for?
Maintaining blood glucose levels
60
How big are glycogen granules?
0.1 µm
61
How big are mitochondria?
10 µm
62
Where can muscle glycogen be used?
Only within muscle
63
Why can muscle glycogen only be used within muscle?
Muscle cells are missing glucose-6 phosphotase
64
What can help enhance glycogen stores?
Carb loading
65
What benefits does carb loading have?
- Has been shown to be beneficial for endurance athletes - Prolongs time to fatigue and protects against exercise-induced hypoglycaemia
66
What are glycogen storage diseases?
Inherited metabolic disorders involving a deficiency of one of the enzymes responsible for glycogen synthesis or breakdown
67
What can a glycogen storage disease lead to?
an abnormal accumulation or deficiency of glycogen in liver or muscles
68
What are some potential symptoms from glycogen storage diseases
hypoglycemia, ketosis, muscle cramps and fatigue, enlarged liver (hepatomegaly), growth retardation in children.

BIOC192 2024 (35 decks)

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