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Metabolism > Storage > Flashcards

Storage Flashcards

1
Q

How is glycogen stored in muscles?

A

As intra- and intermyofibrillar glycogen granules

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2
Q

How is glycogen stored in the liver?

A

As granules within hepatocytes

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3
Q

Which glycosidic bonds form the branches in glycogen?

A

alpha -1,6 glycosidic bonds

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4
Q

Where do the glycogen chains originate from?

A

The dimer of the protein glycogenin.

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5
Q

How often do branch points occur in glycogen?

A

Every 8-10 residues

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6
Q

Which molecule is needed to begin glycogenesis?

A

Glucose-6-phosphate

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7
Q

What is the sequence of molecules for glycogenesis?

A

Glucose -> glucose-6-phosphate -> glucose-1-phosphate -> UDP-glucose -> glycogen

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8
Q

What is the role of phosphoglucomutase?

A

Conversion of glucose-6-phosphate to glucose-1-phosphate at the beginning to glycogenesis.

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9
Q

What are the main enzymes required for glycogenesis?

A

Glycogen synthase

Branching enzyme

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10
Q

What are the main enzymes required for glycogenolysis?

A

Glycogen phosphorylase

Debranching enzyme

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11
Q

Can phosphoglucomutase be used reversibly?

A

Yes

It is used in glycogenesis and glycogenolysis.

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12
Q

What is the end point of glycogenolysis in muscle and liver?

A

Glucose-6-phosphate is created in both circumstances but in the muscles G6P is immediately used for glycolysis whereas in the liver it is converted back to glucose.

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13
Q

What is the effect of glucagon on glycogen?

A

liver: activates glycogen breakdown by increases phosphorylation by glycogen phosphorylase
muscle: glucagon has no effect

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14
Q

What is the effect of insulin on glycogen?

A

Activates glycogen synthesis by increasing dephosphorylation by glycogen synthase.

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15
Q

Does AMP activate glycogen phosphorylase?

A

Yes

but only in the muscle not in the liver.

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16
Q

What is the difference between the glycogen phosphorylase of the liver and the one of the muscle?

A

They are coded for by different genes

17
Q

What is Von Gierke’s disease?

A

glucose-6-phosphatase deficiency

glycogen storage disease

18
Q

What is McArdle disease?

A

muscle glycogen phosphorylase deficiency

glycogen storage disease

19
Q

When does gluconeogenesis begin?

A

Beyond 8 hours of fasting

20
Q

What are the precursors of gluconeogenesis?

A

lactate, glycerol and glucogenic amino acids

21
Q

What is the Cori Cycle?

A

The conversion of glucose to lactate in muscle which is then reversed in the liver.

22
Q

What are the key enzymes of gluconeogenesis?

A

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

23
Q

What is the role of PEPCK?

A

PEPCK is the enzyme used to reverse step 10 of glycolysis through the production of oxaloacetate. This is because the enzyme of step 10 is irreversible.

24
Q

What does fructose-1,6-bisphosphatase do?

A

the opposite of phosphofructokinase

reversal of step 3 of glycolysis

25
Q

What kind of reaction synthesises TAG?

A

esterification

26
Q

How is TAG stored?

A

In anhydrous form as it is hydrophobic.

Within adipocytes.

27
Q

What is hyperplasia?

A

An increase in cell number

28
Q

Where does fatty acid synthesis occur?

A

Liver

29
Q

Why is acetyl coA converted to citrate during fatty acid synthesis?

A

Acetyl-CoA is too big to leave the mitochondria so must be converted to citrate first. Citrate is then cleaved in the cytoplasm.

30
Q

What is the role of acetylcoA carboxylase?

A

Prodution of malonyl coA from acetyl coA

31
Q

What is the role of the fatty acid synthase complex?

A

Building fatty acids by the sequential addition of 2 carbon units.
Requires ATP and NADH.

32
Q

What increases the activity of the fatty acid synthase complex?

A

Insulin and citrate

33
Q

What decreases the activity of the fatty acid synthase complex?

A

Glucagon
Adrenaline
AMP

34
Q

By which mechanism do hormones change the activity of enzymes?

A

Covalent modification

35
Q

By which mechanism do citrate and AMP alter enzyme activity?

A

Allosteric

36
Q

Which tissues have an absolute requirement for glucose?

A

erythrocytes, leukocytes, testes, kidney medulla and lens and cornea of eye

Metabolism (17 decks)

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