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MEH > Energy Storage (Glycogen And Fat) > Flashcards

Energy Storage (Glycogen And Fat) Flashcards

1
Q

What are the tissues which have an absolute requirement for glucose?

A

Red blood cells
Neutrophils
Innermost cells of kidney medulla
Lens of eye

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2
Q

Why do RBCs have an absolute requirement for glucose?

A

No mitochondria so need glucose for glycolysis for energy

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3
Q

What levels of glucose in hypoglycaemia lead to confusion?

A

2.8mmol/L

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4
Q

What is the name of the polymer which is a store of glucose?

A

Glycogen

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5
Q

Where and how is glycogen stored?

A

Muscles (mainly skeletal)
Liver
Store as granules

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6
Q

How are glucose residues linked together?

A

By alpha 1-4 and alpha 1-6 glycosidic bonds

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7
Q

What are the 4 steps of Glycogenesis?

A

Glucose phosphorylated to glucose-6-phosphate by Hexokinase

Glucose 6-phosphate converted to Glucose 1 phosphate by phosphoglucomutase

Glucose 1-phosphate converted to UDP-glucose by G1P uridyltransferase

UDP-glucose added to glycogen to extend the length of glycogen

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8
Q

What are the 2 enzymes involved in the 4th step of Glycogenesis?

A

Glycogen synthase forms a 1-4 glycosidic bonds
Branching enzyme forms a 1-6 glycosidic bonds

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9
Q

Describe the 1st step of glycogenolysis in its 2 step process stating which enzymes could be involved

A

Phosphate is added to glycogen forming Glucose 1-phosphate and a shortened glycogen
The 2 enzymes involved depend on which glycosidic bond is being broken

Glycogen phosphorylase breaks a 1-4 glycosidic bond
Debranching enzyme breaks a 1-6 glycosidic bond

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10
Q

Describe the 2nd step of glycogenolysis stating which enzyme is involved:

A

Glucose 1-phosphate is converted into Glucose-6-phosphate by Phosphoglucomutase

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11
Q

How is the glucose-6-phosphate utilised in the muscle?

A

Enters glycolysis to produce energy

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12
Q

How is glucose 6 phosphate utilised in the liver?

A

Gets converted into glucose and is released into the blood

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13
Q

What enzyme catalyses the conversion of Glucose-6-phosphate into Glucose?

A

Glucose-6-Phosphatase

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14
Q

What is the function of the glycogen stores in the liver?

A

Acts as a buffer to blood glucose levels

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15
Q

What is the function of glycogen in the muscles?

A

Energy for the muscle since the muscles lack glucose-6-Phosphatase so the glucose-6-phosphate is trapper in the muscle

Enters glycolysis

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16
Q

What is the transporter which takes up glucose in skeletal muscle?

A

GLUT 4

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17
Q

What is the name of the transporter which takes up glucose in the liver?

A

GLUT 2

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18
Q

What are the 2 key enzymes that are regulated to control liver glycogen metabolism?

A

Glycogen synthase (synthesis)
Glycogen phosphorylase (degradation)

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19
Q

What are the affects of Glucagon and adrenaline on the activity of glycogen synthase and glycogen phosphorylase?

A

Glycogen synthase = decreased activity
Glycogen phosphorylase = increased activity

20
Q

What is the effect that insulin has on the activity of glycogen synthase and glycogen phosphorylase?

A

Glycogen synthase = increased activity
Glycogen phosphorylase = inhibited activity

21
Q

Why does glucagon have no affect on muscle glycogen?

A

Have no glucagon receptors

22
Q

Give 2 examples of Glycogen storage diseases

A

Von Gierkes disease
McArdle disease

23
Q

What is Von Gierkes disease?

A

Glucose-6-Phosphatase deficiency

24
Q

What is the problem with being deficient in glucose-6-Phosphatase in Von Gierkes disease?

A

Liver can no longer act as a storage of glucose for the blood
Glucose 6 phosphate cannot be converted to glucose so it gets stuck in the liver
Can lead to hypoglycaemia

25
Q

What enzyme is deficient in McArdle disease?

A

Muscle glycogen phosphorylase

26
Q

What is Gluconeogenesis?

A

The production of new glucose

27
Q

When does Gluconeogenesis take place ?

A

After 8 hours of fasting (once liver glycogen stores are depleted)

28
Q

Where does Gluconeogenesis take place?

A

Liver
Small amount in kidney cortex

29
Q

What are the 3 major precursors for Gluconeogenesis?

A

Lactate
Glycerol
Glucogenic amino acids

30
Q

What are the 3 key enzymes involved in Gluconeogenesis?

A

PEPCK
Fructose 1,6-bisphosphatase
Glucose-6-Phosphatase

31
Q

Which are the 2 key regulatory enzymes of Gluconeogenesis?

A

PEPCK
Fructose 1,6-bisphosphatase

32
Q

What affect does Glucagon and cortisol have on PEPCK and Fructose 1,6-bisphosphatase and so their affect on Gluconeogenesis?

A

PEPCK = increased amount
Fructose 1,6-bisphosphatase = increased amount and activity

STIMULATES GLUCONEOGENESIS

33
Q

What affect does Insulin have on PEPCK and Fructose 1,6-bisphosphatase and so their affect on Gluconeogenesis?

A

PEPCK = Decrease amount
Fructose 1,6-bisphosphatase = decreased amount and activity

INHIBITS GLUCONEOGENESIS

34
Q

What type of control is the storage and utilisation of TAGs under?

A

Hormonal

35
Q

What do adipocytes do?

A

Store Triacylglycerols and cholesterol esters

36
Q

Quick overview on how TAG are metabolised

A

TAG broken down in small intestine to Glycerol and fatty acids
Converted back into TAG and packaged into Chylomicrons
Chlyomicrons transport TAG via lymph
Chylomicrons then enter blood then transfer TAG to tissues to generate energy via fatty acid oxidation
Or TAG stored in adipose tissue
Hormone sensitive Lipase breaks down TAG
Fatty acids transported as FA albumin complex to tissues for B oxidation

37
Q

What is Lipogenesis?

A

Fatty acid synthesis

38
Q

Where does Fatty acid synthesis mainly occur?

A

Liver

39
Q

Where does fatty acid synthesis take place in the cell?

A

In cytoplasm

40
Q

Describe briefly fatty acid synthesis

A

Glycolysis makes pyruvate (cytoplasm)
Pyruvate moves into mitochondria forming citrate
Citrate moves out of mitochondria back into cytoplasm
Citrate cleaved back into Acetyl CoA and Oxaloacetate
Acetyl CoA made into Malonyl CoA by enzyme Acetyl CoA carboxylase
Fatty acid synthase complex builds fatty acids by adding 2 carbon units from Malonyl CoA

41
Q

What is the key enzyme which converts Acetyl-CoA into Malonyl-CoA?

A

Acetyl-CoA carboxylase

42
Q

What is the enzyme complex that builds the fatty acid chain by adding 2 carbons every cycle from Malonyl-CoA?

A

Fatty acid synthase complex

43
Q

How does Fatty acid oxidation differ to Fatty acid synthesis?

A

Ox = removes 2 Cs every cycle as Acetyl CoA
Synthesis = add 2 Cs every cycle as Malonyl CoA

Ox = produces Acetyl CoA
Synthesis = Consumes Acetyl CoA

Ox= mitochondria
Synthesis = cytoplasm

Ox = produces NADH and FADH2
Synthesis = require NADPH

44
Q

What is hormone sensitive Lipase?

A

Enzyme regulated by hormones which breaks down Triacylglycerols

45
Q

Which hormones influence Hormone sensitive Lipase?

A

Glucagon and Adrenaline = Stimulates
Insulin = inhibits

MEH (33 decks)

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