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MEH > Energy Storage > Flashcards

Energy Storage Flashcards

1
Q

Which tissue have an absolute requirement for glucose?

A

Red blood cells
Neutrophils
Kidney medulla
Lens of eye

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2
Q

What glucose stored as?

A

Glycogen

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3
Q

What is glycogen stored as?

A

Granules

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4
Q

What are the two types of structure on a glycogen molecule?
At what bond?

A

Branch points A-16

Chains A-14

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5
Q

What does glycogen originate from?

A

A dimer of the protein glycogenin

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6
Q

What is the process of glycogen production?

A

Glycogenesis

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7
Q

What is the process of glycogen breakdown?

A

Glycogenolysis

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8
Q

What is the importance of the structure of glycogen?

A

Multiple points where enzymes can release glucose monomers

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9
Q

What are the key enzymes in glycogenesis?

A

Hexokinase - glucokinase in liver

Glycogen synthase
Branching enzyme

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10
Q

What does hexokinase catalyse?

A

Glucose to glucose 6 phosphate

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11
Q

What are the functions of glycogen synthase and branching enzyme?

A

Synthase - extends the chain

Branching - makes it branched

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12
Q

What are the two key enzymes in glycogenolysis that break down glycogen into glucose 1 phosphate?

A

Glycogen phosphorylase

De-branching enzyme

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13
Q

What do different enzymes in glycogen synthesis and degradation allow?

A

Simultaneous inhibition

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14
Q

What happens to glucose 6 phosphate in muscle cells?
Why?

A

Used in glycolysis

They lack g6phosphatase - so it cannot be broken down into glucose

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15
Q

What happens to glucose 6 phosphate in liver cells?

A

Broken down by g6phosphatase into glucose

Glucose is transported in the blood to other tissues

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16
Q

What does glycogen act as in liver cells?

A

Buffer of blood glucose levels

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17
Q

What are the two rate limiting enzymes in glycogen metabolism - in the liver?
In which recess are they in?

A

Glycogen synthase - synthesis
Glycogen phosphorylase - degradation

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18
Q

What hormones regulate liver glycogen metabolism?

A

Glucagon, adrenaline

Insulin

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19
Q

Describe the effect of glucagon and adrenaline on glycogen metabolism

A

Synthase - decreases
Phosphorylase - increases

20
Q

Describe the effect of insulin on glycogen metabolism

A

Synthase - increases
Phosphorylase - decreases

21
Q

What is the difference between the regulation of glycogen metabolism in muscle and liver cells?

A

Glucagon has no effect in muscle cells

AMP is an allosteric activator of glycogen phosphorylase

22
Q

How do glycogen storage diseases arise?

A

Deficiency or dysfunction of enzymes of glycogen metabolism

23
Q

Describe the effects of excess and diminished glycogen storage

A

Excess - tissue damage

Diminshed - hypoglycaemia and poor exercise tolerance

24
Q

Explain two key examples of glycogen storage diseases

A

Von gierke - g6phosphatase deficiency

McArdle - muscle glycogen phosphorylase deficiency

25
Q

What word describes the synthesis of glucose

A

Gluconeogenesis

26
Q

When does gluconeogenesis occur?
Where?

A

Beyond 8 hours of fasting

Liver and to a lesser extent in the kidneys

27
Q

What are the three main precursors of gluconeogenesis?

A

Lactate

Glycerol - from adipose tissue from the breakdown of triglycerides

Amino acids

28
Q

What are the three key enzymes in gluconeogenesis?

A

G6Phosphatase
F16biphosphatase
PEPCK

29
Q

What are the two regulatory enzymes in gluconeogenesis?
What are they in response to? (3)

A

Fructose16bisphosphatase
PEPCK

Starvation, prolonged exercise, stress

30
Q

What are the two hormones that effect gluconeogenesis?

A

Glucagon, cortisol
Insulin

31
Q

Describe the effect of insulin on gluconeogenesis

A

PEPCK and F16BP decreases
Inhibits

32
Q

Describe the effect of glucagon and cortisol on gluconeogenesis

A

PEPCK and F16BP increases
Stimulated

33
Q

What is the three step timeline of glucose utilisation?

A

Glucose consumed from food
Glycogenolysis
Gluconeogenesis

34
Q

What is excess ‘energy’ stored as?
Where?

A

Triacylglycerol

Adipose tissue

35
Q

Why is triacylglycerol stored in adipose tissue?

A

Hydrophobic
So stored in anhydrous form

36
Q

What is the storage of triacylglycerols controlled by?
When are they mobilised?

A

Hormone

Prolonged excercise, starvation, pregnancy

37
Q

What is a key feature of adipocytes?

A

Organelles pushed to the edge

38
Q

Where does fatty acid oxidation not occur?

A

Cells lacking mitochondria

Brain - do not pass blood brain barrier

39
Q

What is the process of fatty acid synthesis?
Where does it occur?

A

Lipogenesis

Liver

40
Q

What are the 5 steps of lipogenesis?

A
  1. Glycolysis - glucose to pyruvate
  2. Pyruvate enters mitochondria and forms acteylCoA and oxaloacetate
  3. AcetylCoA and oxaloacetate condense to form citrate
  4. Citrate enters cytoplasm and is broken into oxaloacetate and acetylCoA
  5. AcetylCoA is converted to malonly CoA by AcetylCoA carboxylase
  6. Fatty acid synthase complex aids the addition of 2C units provided by malonylCoA
41
Q

What two things does lipogenesis require?

A

ATP
NADPH

42
Q

What is the key regulatory enzyme in liver lipogenesis?
What hormones control it?

A

AcetylCoA carboxylase

Insulin + citrate - increase
Glucagon and adrenaline + AMP - decrease

43
Q

What 4 differences between fatty acid oxidation and synthesis?

A

O - removes C2 S - add C2
O - in mitochondria S - in cytoplasm
O - insulin inhibits S - insulin stimulates
O - oxidative (produces NADH, FAD2H) S - reductive (requires NADPH)

44
Q

What is the process of triacylglycerols being broken down?
Into what?

A

Lipolysis

Glycerol
Fatty acids

45
Q

What happens to glycerol during lipolysis?

A

Travels to liver
Source of C for gluconeogenesis

46
Q

What happens to fatty acids during lipolysis?

A

Travels complexed with albumin
To muscle and tissues

For B oxidation

MEH (10 decks)

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