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Ellie's MEH > Sesh 4- Energy Storage > Flashcards

Sesh 4- Energy Storage Flashcards

1
Q

List 4 types of cells that have an absolute requirement for glucose

A
  1. Red blood cells
  2. Neutrophils
  3. Cells in lens of eye
  4. Innermost cells of renal medulla
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2
Q

Where is glycogen stored?

A

As granules in skeletal muscle and the liver

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3
Q

What is the purpose of glycogen in the liver?

A

Can be mobilised to maintain blood glucose levels

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4
Q

What is the purpose of glycogen in skeletal muscle?

A

Can enter glycolysis in muscle, to generate ATP for muscle contraction

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5
Q

Why can’t glycogen stored in skeletal muscle be mobilised to help maintain plasma glucose levels?

A

Muscles lacks glucose-6-phosphatase that converts G-6-P to glucose

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6
Q

Give 2 reasons why glycogen’s branched structure is advantageous

A
  1. Less osmotic effect as stored as 1 molecule

2. Lots of places for enzymes to act for quick glucose release

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7
Q

What does phosphoglucomutase do?

A

Converts G-6-P to G-1-P in the 2nd step of glycogenesis

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8
Q

Which 2 enzymes catalyse the final step of glycogenesis?

A
  1. Branching enzyme forms alpha-1,6, bonds

2. Glycogen synthase forms alpha-1,4 bonds

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9
Q

What are the 2 enzymes involved in the first step of glycogenolysis?

A
  1. Debranching enzyme

2. Glycogen phosphorylase

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10
Q

What effect does glucagon have on the enzymes involved in glycogen metabolism?

A

Phosphorylates enzymes which…

  • reduces glycogen synthase activity
  • increases glycogen phosphorylase activity
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11
Q

What effect does insulin have on the enzymes involved in glycogen metabolism?

A

Dephosphorylates enzymes which…

  • increases glycogen synthase activity
  • reduces glycogen phosphorylase activity
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12
Q

What effect does glucagon have on muscle glycogen stores?

A

None, as muscle doesn’t have glucagon receptors.

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13
Q

How is muscle glycogen phosphorylase activated?

A

Allosterically by AMP

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14
Q

What is von Gierke’s disease?

A
  • Congenital deficiency of glucose-6-phosphatase

- Cannot convert G-6-P from liver to glucose, so get hepatomegaly

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15
Q

What is McArdle disease?

A
  • Congenital deficiency in muscle glycogen phosphorylase

- Can’t mobilise glucose from muscle glycogen, so present with sever lethargy

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16
Q

Roughly how long after fasting does gluconeogenesis kick in?

A

8 hrs, once liver glycogen stores have been depleted

17
Q

Name the 2 places gluconeogenesis can occur

A
  1. Liver (mainly)

2. Renal cortex

18
Q

What are the 3 major precursors for gluconeogenesis?

A
  1. Lactate
  2. Glycerol
  3. Amino acids (mainly alanine)
19
Q

What is the role of PEPCK in gluconeogenesis?

A

Converts oxaloacetate to PEP in 1st stage

20
Q

What is the role of fructose 1,6, bisphosphatase in gluconeogenesis?

A

Converts fructose 1,6-bisphosphate to fructose-6-phosphate

21
Q

What is the role of glucose-6-phosphatase in gluconeogenesis?

A

Converts G-6-P to glucose in final step

22
Q

Which 2 enzymes are the major control points of gluconeogenesis?

A
  1. PEPCK

2. Fructose-1,6 bisphosphatase

23
Q

What are the effects of glucagon and cortisol on gluconeogenesis?

A

Both stimulate it by:

  • Increasing amount of PEPCK
  • Increasing amount and activity of fructose-1,6-bisphosphatase
24
Q

What are the effects of insulin on gluconeogenesis?

A

Inhibits it by:

  • Reducing amount of PEPCK
  • Reducing amount and activity of fructose-1,6-bisphosphatase
25
Q

How long after feeding would glycogenolysis occur?

A

Between 2 and 10 hrs

26
Q

Do adipocytes increase in size or number first when having to store excess lipid?

A

Size

27
Q

Which hormone is released by adipocytes that signals the status of fat stores?

A

Leptin

28
Q

Where is the main site of lipogenesis?

A

The liver

29
Q

What is the key regulatory enzyme of lipogenesis and what does it do?

A

Acetyl CoA carboxylase catalyses conversion of acetyl Co A to malonyl CoA.

30
Q

What effect does insulin have on acetyl CoA carboxylase activity?

A

De-phosphorylates it to increase its activity (i.e. stimulates lipogenesis)

31
Q

What effect does citrate have on acetyl CoA carboxylase?

A

Allosterically stimulates it

32
Q

What is the importance of malate shuttling in lipogenesis?

A

Produces NADPH needed to protect against oxidative stress and to provide fatty acid synthase complex with reducing power.

33
Q

Where in the cell does lipogenesis occur?

A

Cytosol

34
Q

Does beta oxidation of fatty acids or fatty acid synthesis require a higher input of ATP?

A

Fatty acid synthesis (beta oxidation only needs small amounts of ATP to activate fatty acids)

35
Q

How much TAG is normally stored in a 70Kg man?

A

15 Kg

36
Q

Where is the most glycogen in the body stored?

A 
Skeletal muscle (300g) 
NB: Liver only stores ~100g

Ellie's MEH (12 decks)

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