Glycogen

Question 1

Glycogen is the storage form of _________ in animals

Answer 1

carbohydrate

Question 2

where are the primary storage sites of glycogen

Answer 2

liver and skeletal muscle

Question 3

many glucoses bound together is called a what

Answer 3

polymer

Question 4

chains of glucose are connected by

Answer 4

alpha 1,4 glycosidic bonds

Question 5

branch points are formed by

Answer 5

alpha 1,6 glycosidic bonds

Question 6

branching occurs approximately every ____ glucoses

Answer 6

10

Question 7

what is the maximal size of a glycogen granule

Answer 7

55,000 glucose molecules

Question 8

what is proglycogen

Answer 8

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

Question 9

what is macroglycogen

Answer 9

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

Question 10

can skeletal muscle release glucose

Answer 10

no. it lacks the enzyme needed to release glucose.

Question 11

can liver release glucose

Answer 11

yes

Question 12

where is glycogen stored

Answer 12

CYTOSOL

Question 13

what is the initiation phase of glycogen synthesis

Answer 13

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

Question 14

how many ATP’s are broken down to make G6P

Answer 14

1

Question 15

___________ is broken down to create UDP glucose

Answer 15

pyrophosphate

Question 16

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

Answer 16

3

Question 17

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

Answer 17

gluco/hexokinase

Question 18

what enzyme elongates the chain and what bond does it form

Answer 18

glycogen synthase; alpha 1,4

Question 19

what enzyme branches the chain and what bond does it form

Answer 19

glucosyl 4:6 transferase; alpha 1,6

Question 20

Glycogen is broken down into glucose by what enzyme

Answer 20

glycogen phosphorylase

Question 21

G1P–>G6P

Answer 21

phosphoglucomutase

Question 22

the breakdown of glycogen will continue until when

Answer 22

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

Question 23

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

Answer 23

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

Question 24

Glycogen is regulated by what two enzymes

Answer 24

glycogen synthase and glycogen phosphorylase

Question 25

what stimulates glycogen phosphorylase

Answer 25

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

Question 26

what stimulates glycogen synthase

Answer 26

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

Question 27

glucagon shuts down glycogen _______ and activates glycogen_______

Answer 27

synthesis; breakdown

Question 28

what is the most potent stimulator of glycogen

Answer 28

glycogen levels within muscle

Question 29

what effects does exercise have on glycogen

Answer 29

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

Question 30

what happens to glycogen after intense exercise

Answer 30

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)

Question 31

explain the rapid phase of glycogen synthesis

Answer 31

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

Question 32

explain the slow phase of glycogen synthesis

Answer 32

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

Question 33

explain the insulin independent phase

Answer 33

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

Question 34

explain the insulin dependent phase

Answer 34

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

Question 35

If high glycemic carbohydrates are consumed after exercise what happens

Answer 35

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

Question 36

consumption of carbohydrate after exercise _______ glycogen synthesis

Answer 36

increases

Question 37

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

Answer 37

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

Question 38

what type of protein impacts muscle glycogen levels the most

Answer 38

whey protein hydrolysates

Question 39

intense workout compared to moderate burns more fat or carbs?

Answer 39

carbs

Question 40

explain the glycemic index

Answer 40

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)

Question 41

explain the glycemic load

Answer 41

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

Question 42

what happens to insulin during exercise

Answer 42

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

Question 43

Glucokinase has a ______ km than hexokinase

Answer 43

higher

Question 44

what is the main endogenous source of glucose

Answer 44

the liver

Question 45

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

Answer 45

insulin will not cause the liver to take in glucose

Question 46

what role does fructose play in glycogen synthesis

Answer 46

no benefit for muscle glycogen synthesis

Question 47

low doses of fructose _______ liver glycogen synthesis

Answer 47

increase

Question 48

Why are high levels of fructose not good

Answer 48

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

Question 49

what are the enzymes for glycogen synthesis

Answer 49

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

Question 50

what are the enzymes for glycogen breakdown

Answer 50

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

Question 51

what conditions will you experience glycogen synthesis

Answer 51

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

Question 52

what conditions will you experience glycogen breakdown

Answer 52

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