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Biochem Exam 2 > Glycogen > Flashcards

Glycogen Flashcards

1
Q

Glycogen is the storage form of _________ in animals

A

carbohydrate

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2
Q

where are the primary storage sites of glycogen

A

liver and skeletal muscle

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3
Q

many glucoses bound together is called a what

A

polymer

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4
Q

chains of glucose are connected by

A

alpha 1,4 glycosidic bonds

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5
Q

branch points are formed by

A

alpha 1,6 glycosidic bonds

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6
Q

branching occurs approximately every ____ glucoses

A

10

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7
Q

what is the maximal size of a glycogen granule

A

55,000 glucose molecules

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8
Q

what is proglycogen

A

it is more sensitive to dietary carbohydrate and synthesized more rapidly following post exercise glycogen depletion

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9
Q

what is macroglycogen

A

synthesis is slower and more constant. synthesis may last for at least 48 hours post exercise. responsible for carbohydrate loading

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10
Q

can skeletal muscle release glucose

A

no. it lacks the enzyme needed to release glucose.

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11
Q

can liver release glucose

A

yes

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12
Q

where is glycogen stored

A

CYTOSOL

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13
Q

what is the initiation phase of glycogen synthesis

A

glucose–> G6P–>G1P. G1P is combined with UTP and that makes UDP glucose. Now it is ready to be added onto the chain. To initiate a chain, glycogenin is used by the enzyme glycogen initiator synthase

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14
Q

how many ATP’s are broken down to make G6P

A

1

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15
Q

___________ is broken down to create UDP glucose

A

pyrophosphate

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16
Q

how many ATP’s are broken down to attach one glucose

A

3

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17
Q

what is the very first enzyme glucose meets when it enters a cell?

A

gluco/hexokinase

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18
Q

what enzyme elongates the chain and what bond does it form

A

glycogen synthase; alpha 1,4

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19
Q

what enzyme branches the chain and what bond does it form

A

glucosyl 4:6 transferase; alpha 1,6

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20
Q

Glycogen is broken down into glucose by what enzyme

A

glycogen phosphorylase

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21
Q

G1P–>G6P

A

phosphoglucomutase

22
Q

the breakdown of glycogen will continue until when

A

until there are four glucose molecules left prior to a branch point, phosphorylase is no longer effective at breaking down glycogen

23
Q

what are the two enzymes required to break down the glycogen branches

A

glucosyl (4:4) transferase (removes the outer three glucose molecules) and amylo alpha (1,6) glucosidase (removes the last glucose of the branch. Then glycogen phosphorylase can begin again until it gets 4 away from the next branch point

24
Q

Glycogen is regulated by what two enzymes

A

glycogen synthase and glycogen phosphorylase

25
Q

what stimulates glycogen phosphorylase

A

low ATP, high AMP/ADP, low glucose, glucagon (liver), muscle contraction (calcium)

26
Q

what stimulates glycogen synthase

A

high energy charge, lots of glucose, insulin, low glycogen levels

27
Q

glucagon shuts down glycogen _______ and activates glycogen_______

A

synthesis; breakdown

28
Q

what is the most potent stimulator of glycogen

A

glycogen levels within muscle

29
Q

what effects does exercise have on glycogen

A

intense exercise burns muscle and liver glycogen. increases GLUT4 translocation, increases GLUT4 transcription-translation, stimulates glycogen synthesis after exercise and increases insulin sensitivity after the exercise

30
Q

what happens to glycogen after intense exercise

A

glycogen synthesis has an initial high rate. maximal activity during the first 30 minutes, and rapid decline to about one fifth by 60 minutes. reduced to about one ninth by 120 minutes. Two reasons: 1. increased glycose uptake (GLUT4’s) 2. increased glycogen enzyme activity (glycogen synthase)

31
Q

explain the rapid phase of glycogen synthesis

A

30-60 min post-exercise. Insulin independent. occurs when muscle glycogen levels are relatively low and carbohydrate is provided immediately after exercise

32
Q

explain the slow phase of glycogen synthesis

A

follows the rapid phase (several hours). Insulin dependent. much slower rate of glycogen synthesis. must have carbs available and insulin

33
Q

explain the insulin independent phase

A

also called rapid phase. less than 3-6 hours post-exercise. AMPK pathway stimulated. PI3K pathway is temporarily inhibited

34
Q

explain the insulin dependent phase

A

also called slow phase. 3-6 to 48 hours post-exercise.

35
Q

If high glycemic carbohydrates are consumed after exercise what happens

A

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

36
Q

consumption of carbohydrate after exercise _______ glycogen synthesis

A

increases

37
Q

ingestion of protein/amino acids in combination with moderate carbohydrate intake post exercise leads to what

A

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

38
Q

what type of protein impacts muscle glycogen levels the most

A

whey protein hydrolysates

39
Q

intense workout compared to moderate burns more fat or carbs?

A

carbs

40
Q

explain the glycemic index

A

increase in blood glucose level over the base-line level during a 2 hour period following the consumption of a defined amount of carbohydrate compared with the same amount of carbohydrate in a reference food (white bread or glucose)

41
Q

explain the glycemic load

A

glycemic index times the grams of carbs in a serving of the food. Considers both quantity and quality of carb in the meal. the higher the GL, the greater the expected elevation in blood glucose and in the insulinogenic effect of the food. This is what you don’t want happening before bed or a workout. By the time you go to bed your blood glucose is crashing. bigger the meal the harder the crash. smaller meals before bed will help blood glucose slowly return instead of crashing

42
Q

what happens to insulin during exercise

A

within minutes of the start of exercise, insulin levels rapidly fall and reach the same low values, regardless of the GI of the pre-exercise meal

43
Q

Glucokinase has a ______ km than hexokinase

A

higher

44
Q

what is the main endogenous source of glucose

A

the liver

45
Q

when blood glucose is in the normal range what effect will insulin have on the liver

A

insulin will not cause the liver to take in glucose

46
Q

what role does fructose play in glycogen synthesis

A

no benefit for muscle glycogen synthesis

47
Q

low doses of fructose _______ liver glycogen synthesis

A

increase

48
Q

Why are high levels of fructose not good

A

liver has a high uptake (50% on first pass) increased fat, lactate and glycerol formation. HFCS and sucrose are not that different

49
Q

what are the enzymes for glycogen synthesis

A

hexo/glucokinase, phosphoglucomutase, UDP glucose pyrophosphorylase, pyrophosphatase, glycogen initiator synthase, glycogen synthase, glucosyl 4:6 transferase

50
Q

what are the enzymes for glycogen breakdown

A

glycogen phosphorylase, phosphoglucomutase, glucosyl (4:4) transferase, amylo alpha (1,6) glucosidase

51
Q

what conditions will you experience glycogen synthesis

A

high blood glucose, insulin, fructose*, low glycogen content, high energy charge, ATP

52
Q

what conditions will you experience glycogen breakdown

A

low blood glucose, glucagon, low energy charge, ADP/AMP, calcium (muscle contraction)

Biochem Exam 2 (6 decks)

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