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Metabolism > Carbohydrate metabolism 1 > Flashcards

Carbohydrate metabolism 1 Flashcards

1
Q

What makes glucose from glycogen

A

Liver

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2
Q

Where does gluconeogenesis take place

A

Liver and Kidney

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3
Q

Where are the main stores of glycogen

A

Skeletal muscle and liver

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4
Q

What are the two ends of glycogen

A
  • one reducing end

- one non reducing end on every branch

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5
Q

What benefit does the non-reducing end have

A

rapid mobilization

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6
Q

Where is the alpha 1-4 linkage found in glycogen

A

ON main chain

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7
Q

Where is the alpha 1-6 linkage found in glycogen

A

On the branches

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8
Q

What are the main enzymes associated with glycogen degradation

A
  • glycogen phosphorylase
  • GLycogen debranching enzyme
  • Phosphoglucomutase
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9
Q

What does glycogen phosphorylase do

A

Turns glycogen into glucose 1-phosphate and remaining glycogen by raw cleavage of alpha 1-4 bonds until 4 glycosyl units remain on branch point (limit dextrin)

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10
Q

What does glycogen phosphorylase cause

A

Allosteric interactions and covalent modifications

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11
Q

What are glycogen phosphorylase inhibitors

A

ATP, G6, GLUCOSE

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12
Q

What is the glycogen phosphorylase activator

A

AMP

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13
Q

what is the glycogen deb ranching enzyme like

A

Bifunctional with separate active sites

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14
Q

What does he glycogen deb ranching enzyme do

A

Breaks alpha 1-4 glycosidic bond and then adds that to the end of the glycogen branch
-then removes the remaining branch using amylo alpha 1-6 glucosidase

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15
Q

What does phosphoglucomutase do

A

Turns glucose 1-phosphate to glucose 1,6 diphosphate, then that to glucose 6 phosphate

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16
Q

What can happen to glucose 6 phosphate

A

Can continue along the glycolytic pathway or the pentose pathway

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17
Q

What can glucose 6 phosphate by hydrolysed by and where

A

By glucose 6 phosphatase to glucose in the bloodstream

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18
Q

What can glycogen be turned into

A

Glucose 6-phosphate

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19
Q

What can happen to glucose 6 phosphate

A
  • Turned to glucose
  • Turned to ribose 5 phosphate (pentose phosphate pathway)
  • Undergo glycolysis to turn into pyruvate
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20
Q

What can happen to pyruvate

A
  • Can be turned into glucose-6 phosphate by gluconeogenesis
  • Can be turned to amino acids
  • Can be turned into acetyl CoA
  • Can turned into lactate
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21
Q

What can happen to acetyl-CoA

A

Can go onto the citric acid cycle

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22
Q

What happens to glucose 6 phosphate produced by gluconegenesis

A

Can’t be hydrolysed to glucose but can be converted to G1P for incorporation into glycogen

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23
Q

What does glycogen synthase do

A

Makes alpha 1-4 linkages

-only extends existing chains

24
Q

What does glycogenin do

A

Attach to glucose

25
Q

How are glucose levels regulated in the liver

A
  • Glycogenesis accelerates during well fed states

- Glycogenolysis accelerates during fasting

26
Q

How are glucose levels regulated in skeletal muscles

A
  • Glycogenesis accelerates during rest periods

- Glycogenolysis accelerates during exercise

27
Q

How are glycogen synthase and glycogen phosphorylase regulated

A
  • Hormonally regulated via phosphorylation/dephosphorylation

- Allosterically regulated

28
Q

How do hormones act

A

Through changes to phosphorylation state of enzymes

29
Q

What acts through a second messenger model

A

Cyclic AMP

30
Q

What does adrenaline act on

A

MUScle and liver

31
Q

What does glucagon act on

A

Liver

32
Q

What is the role of Calcium in muscle and glucose regulation

A
  • During contraction, released and binds to Calmodulin subunit of phosphorylase kinase (and activates it)
  • Phosphorylase kinase can then activate glycogen phosphorylase causing glycogen degredation
33
Q

What does phosphorylase kinase do to glycogen phosphorylase

A

Activates it causing glycogen degredation

34
Q

What is the active form of glycogen synthase

A

Dephosphorylated

35
Q

How is glycogenolysis regulated hormonally

A

-Ca2+ in muscle
-AMP in muscle
-

36
Q

How does AMP regulate glycogenolysis

A

Its present in muscle in extreme conditions of anoxia and depletion of ATP

-amp activates glycogen phosphorylase b without it being phosphorylated

37
Q

How is glycogenesis regulated hormonally

A

By glycogen synthase (active form is dephosphorylated)

38
Q

What enzymes are allosterically regulated for regulation of glucose

A
  • glycogen synthase

- glycogen phosphorylase

39
Q

When is gluconeogenesis inhibited

A

-Substrate and energy levels high

40
Q

When is glycogenolysis increased

A

-GLucose and energy levels are low

41
Q

Does allosteric regulation or hormonal regulation override the other

A

Allosteric can override hormone-mediated covalent regulation

42
Q

IN a high energy state, what are the concentrations of

  • glucose
  • G6P
  • ATP

like

A
  • glucose = high
  • G6P = high
  • ATP = high
43
Q

IN a low energy state, what are the concentrations of

  • glucose
  • G6P
  • ATP
  • muscle AMP

like

A
  • glucose = low
  • G6P = low
  • ATP = low
  • Muscle AMP = high
44
Q

In a high energy state, what do G6P and ATP (and glucose in liver) inhibit

A

Glycogen phosphorylase

45
Q

In a high energy state, what is activated by G6P

A

Glycogen synthase

46
Q

In a high energy state, what predominates

A

Glycogen synthesis

47
Q

IN a low energy state, what is activated by AMP

A

Muscle glycogen phosphorylase

48
Q

What predominates in a low energy state

A

GLycogenolysis

49
Q

What is glycogenolysis in muscle activated by

A

Calcium

50
Q

what does muscle contraction from

A

Increased cytosolic calcium

51
Q

What protein acts as a glucose acceptor

A

GLycogenin

52
Q

Which end of the enzymes dismantle glycogen

A

From the non-reducing end

53
Q

How is G6P converted to G1P

A

Phosphoglucomutase

54
Q

How is G1P converted to UDP glucose

A

UDP-glucose pyrophosphorylase

55
Q

What is G1P converted to

A

UDP glucose

56
Q

What is UDP glucose turned into

A

Glucose 1-phosphate molecules stuck together by main chain

57
Q

What molecule turns UDP glucose into Glucose 1 phosphate molecules stuck together by main chain

A

Glycogen synthase

Metabolism (11 decks)

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