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Fundamentals Of Living Cells > Carbohydrate Metabolism > Flashcards

Carbohydrate Metabolism Flashcards

1
Q

What is the critical blood glucose level?

A

2.5 mM

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2
Q

What are the symptoms of hypoglycaemia?

A 
Muscle weakness
Loss of coordination
Mental confusion
Sweating 
Hypoglycaemic coma and death
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3
Q

What are the hyperglycaemic symptoms?

A

Non enzymatic modification of proteins which could lead to cataracts
Hyperosmolar coma

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4
Q

What is glycogensis

A

Glycogen synthesis

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5
Q

How much glycogenesis takes place (in grams) in the liver and skeletal muscle?

A

100g in liver

300-400g in skeletal muscle

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6
Q

When does glycogenesis take place?

A

When blood glucose levels are high

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7
Q

What is glycogen?

A

Branched polymer of glucose

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8
Q

How is glycogen formed?

A

Alpha 1-4 and 1-6 glycosidic bonds

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9
Q

Where is glycogen formed

A

On a protein primer called glycogenin

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10
Q

What is glycogenesis regulated by?

A

Glycogen synthase

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11
Q

How are the branched points formed?

A

by a branching enzyme

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12
Q

What enzyme performs G6P-G1P

A

Phosphoglucomutase

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13
Q

What enzyme performs G1P+UTP->UDP

A

UDP glucose pyrophosphorylase

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14
Q

What enzyme adds more glucose residues to the glycogenin?

A

Glycogen synthase

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15
Q

How long is the original glycogen chain before branching happens?

A

11 glucose residues

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16
Q

Why is glycogen formed?

A

Glucose is osmotically active so it cant be stored (affects the water potential of the cells)

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17
Q

What is glycogenolysis?

A

Glycogen breakdown

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18
Q

Where does glycogenolysis happen?

A

Liver, muscle and (sometimes) kidney

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19
Q

When does glycogenolysis happen?

A

When glucose levels are low

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20
Q

What is glycogenolysis stimulated by?

A

Glucagon, Adrenaline, noradrenaline, growth hormone

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21
Q

What enzyme breaks the 1-4 glycosidic bonds between the glucose residues?

A

Phosphorylase

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22
Q

What does the breakdown of 1-4 glycosidic bonds produce?

A

G1P

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23
Q

What does phosphoglucomutase facilitate?

A

G1P-G6P

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24
Q

What enzyme removes the last 3 glucose residues on a branch?

A

Transferase

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25
Q

Where do the last 3 glucose residues go when they are debranched?

A

Added to the non-reducing end of the chain

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26
Q

What enzyme breaks the 1-6 glycosidic bonds?

A

Alpha 1-6 glucosidase

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27
Q

What happens to the glucose when it is freed from the glycogen?

A

Phosphorylated by hexokinase in the muscle to form G6P

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28
Q

What breaks down the glucose chains to produce G1P?

A

Phosphorylase

29
Q

In the liver what enzyme does the G6P->glucose reaction?

A

G6-phosphatase

30
Q

What are the products of glycolysis?

A

G1P, glucose

31
Q

What is glycogen phosphorylase?

A

Large multi-subunit enzyme that plays a key role in glycogenolysis

32
Q

What is glycogen phosphorylase regulated by?

A

Allosteric interactions that signal the energy state of the cell

33
Q

What are the two isoforms of glycogen phosphorylase?

A

Active - phosphorylase A

Inactive - phosphorylase B

34
Q

What is phosphorylase A phosphorylated by?

A

Phosphorylase B kinase

35
Q

What inhibits phosphorylase?

A

Insulin

36
Q

What stimulates phosphorylase in the liver?

A

Glucagon

37
Q

What stimulates phosphorylase in the muscle?

A

Adrenaline

38
Q

What weakly stimulates phosphorylase?

A

Cortisol

39
Q

In muscle what can glycogen phosphorylase B be activated by?

A

5’AMP

40
Q

What blocks 5’ AMP activation?

A

ATP and G6P

41
Q

In the liver what is phosphorylase A inhibited by?

A

Glucose

42
Q

When and how is glycogen synthase activated?

A

In times of plenty of glucose, by insulin

43
Q

When and how is glycogen phosphorylase activated?

A

When blood glucose is low, by glucagon, adrenaline and noradrenaline

44
Q

What does the pentose phosphate pathway start and end with?

A

Starts with G6P and ends with ribose 5 phosphate

45
Q

What is ribose 5 phosphate included in?

A

Nucleotide and Nucleic acid synthesis

46
Q

Where is NADPH formed?

A

In the pentose phosphate pathway

47
Q

What is GSH used in?

A

In the protective mechanism of the self and to oxidative stress

48
Q

What is NADPH important to?

A

The formation of GSH and fatty acids

49
Q

What molecules do gluconeogenesis?

A

Triglycerides
Lactate
Amino acids

50
Q

What is gluconeogenesis?

A

Creation of new glucose

51
Q

Where does gluconeogenesis take place?

A

Mainly in the liver and the kidney, but also a bit in the intestine

52
Q

When does gluconeogenesis take place?

A

When the blood glucose levels are very low (fasting or starving)

53
Q

What is gluconeogenesis the reverse of?

A

Glycolysis

54
Q

What enzyme takes pyruvate to oxaloacetic acid?

A

Pyruvate carboxylase

55
Q

What enzyme takes oxaloacetic acid to phosphoenol pyruvate?

A

Phosphoenol pyruvate carboxykinase

56
Q

What enzyme reverses phosphofructokinase?

A

Fructose 1-6 bisphosphate

57
Q

What enzyme reverses hexokinase?

A

Glucose-6-phosphatase

58
Q

Where are the fatty acids fed into the TCA cycle?

A

Glycerol components feed in where F1-6 bisphosphate is split

59
Q

Where is pyruvate synthesised?

A

In the cytosol

60
Q

Where does pyruvate carboxylase work?

A

In the mitochondria

61
Q

3 most important substrates are

A

Amino acids (Alanine)
Lactate
Glycerol from triglycerides

62
Q

What is gluconeogenesis used for?

A

To maintain blood glucose

63
Q

What is the daily requirement for blood glucose?

A

160g

64
Q

What is the daily requirement for blood glucose in the brain?

A

120g

65
Q

What are the total body reserves of glucose?

A

210g

66
Q

What does the gluconeogenic pathway do?

A

Pyruvate to glucose

67
Q

Where does the gluconeogenic pathway take place?

A

Mostly in the liver and a little in the kidney

68
Q

Where does the gluconeogenic pathway take place during starvation?

A

Kidney productions rise to 40% and a little in the liver

Fundamentals Of Living Cells (41 decks)

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