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Biochemistry II Final 181 > Glycogen synthesis > Flashcards

Glycogen synthesis Flashcards

1
Q

What are the primary storage sites of glycogen storage?

A

Liver and Skeletal muscle

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2
Q

What kind of glycosidic bonds are the chains in glycogen?

A

alpha (1-4)

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3
Q

What ind of bonds are the branch points in Glycogen?

A

alpha (1-6)

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4
Q

What are many glucoses bound together called?

A

polymer or granule ( the polymer makes up the glycogen)

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5
Q

When does branching occur in glycogen?

A

every 10 gucose

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6
Q

What does branching in glycogen provide to glucose?

A

increased solubility ad access

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7
Q

What is Maltose?

A

two glucose bonded together by an alpha(1-4) bond

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8
Q

What is the maximal size of a glycogen granule?

A

55,000 glucose molecules

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9
Q

How many tiers of CHO are there in glycogen?

A

twelve

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10
Q

Does the density of carbohydrates increase exponentially with each tier of glycogen?

A

yes

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11
Q

What is the characteristic of the last tier of glycogen?

A

contains 19,000 glucoses (or 34.6% of total glucose)

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12
Q

What size are most glycogen granules?

A

mid-sized

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13
Q

What kind of glycogen is synthesized more rapidly following post-exercise glycogen depletion, reaching a plateau after 24 hours?

A

proglycogen

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14
Q

What glycogen is more sensitive to dietary carbohydrate?

A

proglycogen

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15
Q

Which glycogen synthesis is sower and more consistent?

A

macroglycogen

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16
Q

What glycogen is responsible for carbohydrate loading (supercompensation)?

A

maroglycogen

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17
Q

which glycogen synthesis may last for at least 48 hours post exercise?

A

macroglycogen

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18
Q

How much glycogen can a skeletal muscle hold?

A

400g

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19
Q

How much glycogen can the liver store?

A

100g (the muscle stores 4x what the liver holds)

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20
Q

What amount of glycogen do cells store besides the muscle and liver?

A

relatively small quantities

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21
Q

Why can’t muscle release glucose?

A

it lacks the enzyme to release glucose

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22
Q

Where is glycogen stored?

A

the cytosol

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23
Q

What enzymes phosphorylate glucose?

A

Hexokinase (muscle)

Glucokinase (liver)

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24
Q

What are the steps in initiation of glycogen synthesis?

A
  1. Glucose is turned into glucose 6p
  2. Glucose 6p is converted into glucose 1p
  3. Glucose 1p is combine with UTP to form UDP glucose
  4. Glycogenin is used to start a chain
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25
Q

What is Glycogenin?

A

Glycogenin is a protein that starts the glycogen chain with the amino acid tyrosine

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26
Q

What enzyme adds the glucose to the tyrosine on Glycogenin?

A

Glycogen Initiator Synthase

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27
Q

What enzyme is utilized to transform Glucose 6P to Glucose 1P?

A

phosphoglucomutase

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28
Q

What enzyme is used to make UDP-Glucose from UTP and Glucose 1P?

A

UDP-Glucose Pyophosphorylase

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29
Q

What enzyme adds glucose onto the initiated glycogen chain? (after the first glucose is added)

A

Glycogen synthase

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30
Q

What is the storage form of carbohydrates in animals?

A

Glycogen

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31
Q

The equivalence of how many ATP are used to attach glucose to glycogen?

A

3 (1 from ATP, 1 from UTP and 1 from pyrophosphate)

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32
Q

What enzyme elongates the glycogen chain by adding alpha(1-4) bonds?

A

Glycogen synthase

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33
Q

Where is elongation of the glycogen chain occurring?

A

Cytosol

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34
Q

What enzyme adds branch points to glycogen with alpha (1-6) bonds?

A

Glucosyl 4:6 transferase

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35
Q

Where does the enzyme Glucosyl 4:6 Transferase get the glucose chains to add a branch point?

A

5-8 carbon chains are taken from the end and attached to another glucose molecule in the chain (of glycogen)

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36
Q

How are highly branched structures achieved during glycogen synthesis?

A 
Glycogen Synthase can add (apha(1-4) bonds) glucose molecules to each end (the chain and branch point).  
Additionally alpha(1-6) can be added to growing chains (by 4:6 Transferase)
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37
Q

What are the main enzymes in glycogen regulation?

A 
glycogen synthase (makes glycogen)
glycogen phosphorylase (breaks down glycogen)
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38
Q

What stimulates glycogen synthase?

and in turns inhibits glycogen phosphorylase

A

Lots of ATP (High Energy Charge)
Lots of glucose
Insulin
Low Glycogen Levels

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39
Q

What inhibits glycogen synthase? (and in turn stimulates glycogen phosphorylase)

A 
Low ATP (Low Energy Charge)
Lots of ADP or AMP
Low Glucose
Glucagon (liver)
Muscle contraction (calcium)
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40
Q

What will Glucagon do to glycogen synthesis?

A

Shuts down glycogen synthesis and activates glycogen breakdown

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41
Q

Catecholmines work similarly to what hormone?

A

Glucagon

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42
Q

What is the key enzyme responsible for the synthesis of glycogen?

A

Glycogen synthase

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43
Q

What is a far more potent regulator of glycogen synthase activity than insulin or muscle contraction?q

A

muscle glycogen concentration

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44
Q

When is glycogen synthase released from being bound to part of the glycogen protein complex?

A

when glycogen concentration decreases

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45
Q

What does intense exercise burn?

A

muscle and liver glycogen

46
Q

What effect does exercise have on glycogen synthesis?

A

Increases GLUT4 translocation
Increase GLUT transcription-translation (more transporters)
Stimulates glycogen synthesis after exercise (free glycogen synthase)
Increases insulin sensitivity after the exercise

47
Q

A single bout of resistance exercise decreased muscle glycogen by how much?

A

Type I fibers by 23%

Type II fibers by 42% (type 2 is responsible for hypertrophy)

48
Q

When does glycogen synthesis have an initial high rate?

A

after intense exercise

49
Q

How does glycogen synthesis change after intense exercise?

A
  1. Maximal activity during the first 30 minutes
  2. Rapid decline to about on fifth by 60 minutes
  3. reduced to about 1/9th by 120 minutes
50
Q

What are the two reasons we have huge glycogen synthesis after intense exercise?

A

Increased glucose uptake (GLUT4s)

Increased glycogen enzyme activity (glycogen synthase)

51
Q

Is the the rapid phase of glycogen synthesis insulin dependent or independent?

A

Insulin independed

52
Q

Is the the slow phase of glycogen synthesis insulin dependent or independent?

A

insulin depended

53
Q

When does rapid phase glycogen synthesis occur?

A

30-60 minutes after exercise
Occurs when muscle glycogen levels are relatively low (128-150 mmol/kg) AND carbohydrate is provided immediately after exercise

54
Q

When does slow phase glycogen synthesis occur?

A

Follow the rapid phase (for several hours)

55
Q

What must the slow phase of glycogen have?

A

carbohydrates available and insulin

56
Q

What are the two phases of increased glucose uptake? (think GLUT4)

A

Insulin-independent

Insulin-dependent

57
Q

When does insulin independent glucose uptake occur?

A

less than 3-6 hours minutes after after exercise

58
Q

What is stimulated from Insulin-independent glucose uptake?

A

AMPK pathway

59
Q

What is temporarily inhibited during Insulin-Independent Glucose uptake?

A

PI3K pathway (Phosphatiylinositol 3-kinase)

60
Q

When does Insulin dependent glucose uptake take?

A

3-6 to 48 hours post-exercise

61
Q

What effect will adding CHOs pos exercise do?

A

will increase insulin but will not have an additive effect on glycogen synthase

62
Q

What happens if high glycemic carbohydrates are consumed after exercise?

A

the resultant hyperinsulinemia leads to only a modest increase in glycogen synthase activity.

63
Q

Does exercise alone lead to a twofold increase for the first 30 minutes of recovery?

A

yes

64
Q

Why is it better to immediately eat after exercise?

A

Glycogen synthesis maybe up to 45% slower if food is consumed after two hours

65
Q

When do the number of glucose transporters associated with the sarcolemma return to pre-exercise concentration?

A

Two hours post-exercise (this is why glycogen synthesis slows down if you eat 2 hours after exercise)

66
Q

What is the difference of the rates of glycogen synthesis after exercise with/without food?

A

w/out food = 7-12 mmol/kg dw/h
w/ food = 20-50 mmol/kg dw/h
(eating after exercise increases glycogen synthesis a Minimum of 2x)

67
Q

If you do not eat after exercise where do the substrates come from for glycogen synthesis?

A

you catabolize amino acids to ,make glycogen

68
Q

When are diminishing returns achieved for glycogen synthesis?

A

after 500 kcal of glucose

69
Q

Can consuming more CHOs increase the rate of glycogen synthesis?

A

yes, glycogen synthesis will be increase up to 500kcal of glucose.

70
Q

What will ingestion of protein/amino acids in combination with moderate carbohydrate intake lad to?

A

higher muscle glycogen synthesis rates when compared to the same amount of carbohydrates alone

71
Q

When does the presence of protein/amino acids not increase glycogen synthase rates?

A

when total carbohydrate intake is very high

72
Q

Name the order of proteins from most glycogen synthesis increase to least increase.

A
  1. Whey protein hydrosylates (5.01mg/g)
  2. Whey protein (4.23mg/g)
  3. Branch chain amino acids (3.92mg/g)
  4. Casein hydrosylates (2.73mg/g)
73
Q

What is the difference between a trained cyclist (fit person) to an untrained individual in muscle glycogen storage?

A
  1. Muscle glycogen storage is 2 fold higher in cyclist

2. Glut4 continent is 3 times higher post exercise

74
Q

How is the glycemic load calculated?

A

glycemic index times the grams of carbohydrates in a serving of the food.

75
Q

What two things should be considered for carbohydrates in a meal?

A

the quantity and quality of the carbohydrates in a meal

76
Q

What does a higher glycemic load mean after consumption?

A

a greater expected elevation in blood glucose and in the insulinogenic effect of the food

77
Q

What is associated with increased risk of type 2 diabetes and coronary heart disease with respect to glycogen synthesis?

A

Long-term consumption of a diet with a relatively high glycemic load

78
Q

During what phase are high GI (glycemic index) meals more effective at replenishing muscle glycogen?

A

during the second phase of recovery (slow phase)

79
Q

What are the 2 benefits of low GI pre-exercise meals?

A
  1. Blood glucose levels tend to be higher in the latter phases of prolonged exercise when subjects are fed low GI compared with high GI pre-exercise meals
  2. Low insulin during exercise allows increased FFA concentrations
80
Q

What happens to insulin after beginning to exercise?

A

insulin levels rapidly fall and reach low values regardless of the GI of the pre-exercise meal.

81
Q

What can be used to recover from exhaustive exercises other than a meal?

A

glucose and Glucose/fructose (2:1 ratio) solutions

82
Q

What can a low dose fructose infusion cause?

A

a threefold increase in net hepatic glycogen synthesis exclusively through stimulation of glycogen synthase flux

83
Q

How can glucose tolerance be improved in a glucose containing meal?

A

by adding very low doses of fructose to the meal

84
Q

How is the glycemic load calculated?

A

glycemic index times the grams of carbohydrates in a serving of the food.

85
Q

What two things should be considered for carbohydrates in a meal?

A

the quantity and quality of the carbohydrates in a meal

86
Q

What does a higher glycemic load mean after consumption?

A

a greater expected elevation in blood glucose and in the insulinogenic effect of the food

87
Q

What is associated with increased risk of type 2 diabetes and coronary heart disease with respect to glycogen synthesis?

A

Long-term consumption of a diet with a relatively high glycemic load

88
Q

During what phase are high GI (glycemic index) meals more effective at replenishing muscle glycogen?

A

during the second phase of recovery (slow phase)

89
Q

What are the 2 benefits of low GI pre-exercise meals?

A
  1. Blood glucose levels tend to be higher in the latter phases of prolonged exercise when subjects are fed low GI compared with high GI pre-exercise meals
  2. Low insulin during exercise allows increased FFA concentrations
90
Q

What happens to insulin after beginning to exercise?

A

insulin levels rapidly fall and reach low values regardless of the GI of the pre-exercise meal.

91
Q

What can be used to recover from exhaustive exercises other than a meal?

A

glucose and Glucose/fructose (2:1 ratio) solutions

92
Q

What can a low dose fructose infusion cause?

A

a threefold increase in net hepatic glycogen synthesis exclusively through stimulation of glycogen synthase flux

93
Q

How can glucose tolerance be improved in a glucose containing meal?

A

by adding very low doses of fructose to the meal

94
Q

What has a higher Km, glucokinase or hexokinase?

A

Glucokinase

95
Q

Is glucokinase inhibited by Glucose 6 phosphate?

A

No

96
Q

Small amounts of fructose cause the release of what from a regulatory protein?

A

glucokinase

97
Q

What causes glucokinase to be inhibited by F6P?

A

F6P binds to the regulatory protein

98
Q

What happens when F1P binds to the regulatory protein?

A

Glucokinase is set free and is activated

99
Q

In the fasted state what is the main endogenous source of glucose?

A

the Liver is the main endogenous source of glucose (2 mg/kg/min)

100
Q

What occurs following glucose consumption in Liver glucose metabolism?

A

Liver consumes glucose

Liver removes approximately one-third of an oral carbohydrate load

101
Q

Will insulin cause the liver to take in glucose during normal blood glucose range?

A

Nope

102
Q

Where is the primary site of fructose disposal?

A

Liver

103
Q

How much fructose is extracted by the liver?

A

50% on the first pass

70% total

104
Q

What enzymes are highly expressed in the liver that are essential for fructose metabolism?

A

Fructokinase

Triokinase

105
Q

Does fructose have a benefit for muscle glycogen synthesis?

A

no :(

106
Q

Does fructose benefit liver glycogen synthesis?

A

yes, low doses increase liver glycogen synthesis

107
Q

Why are high levels of fructose not good?

A

Liver has a high uptake

Increased Fat, Lactate and Glycerol formation

108
Q

What are the enzymes for Glycogen synthesis?

A 
Hexokinas and glucokinase
phosphoglucomutase
UDP Glucose Pyrophorylase
pyrophosphatase
Glycogen initiator synthase
Glycogen synthase
Glucosyl 4:6 Transferase
109
Q

What enzymes are used for glycogen breakdown?

A

Glycogen phosphorylase
phosphoglucomutase
Glucosyl (4:4) Transferase
amylo-alpha-(1,6)-glucosidase

110
Q

What conditions stimulate glycogen synthesis?

A 
High blood glucose
Insulin
Fructose (in liver)
Low glycogen content 
High Energy Charge
ATP
111
Q

What stimulates Glycogen breakdown?

A 
Low blood glucose (in liver)
Glucagon (in liver)
Low energy charge
ADP, AMP
Calcium (muscle contraction)

Biochemistry II Final 181 (3 decks)

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