Glycogenesis

Question 1

glycogenesis

Answer 1

glucose converted to glycogen

Question 2

why do we need glycogenesis

Answer 2

to ensure a reserve of quick energy

Question 3

major sites of glycogen synthesis and storage

Answer 3

liver and skeletal muscle
some glycogen in kidneys and heart

Question 4

liver glycogen unique role

Answer 4

can be broken down to glucose to reenter the bloodstream
maintains blood glucose homeostasis

Question 5

skeletal muscle glycogen storage role

Answer 5

majority of glycogen stores bc skeletal muscle is so common

Question 6

which tissue has the greatest concentration of glycogen?

Answer 6

liver

Question 7

glycogen stores in muscle: problem

Answer 7

an energy source that can’t directly contribute to blood glucose levels
muscles don’t have enzyme that converts phosphorylated glucose back into free glucose

Question 8

how does glucose enter the cell?
(step 1 of glycogenesis)

Answer 8

glucose is phosphorylated by hexokinase in muscle or glucokinase in liver to become glucose-6-phosphate

ATP to ADP

Question 9

glycogen is made up of

Answer 9

G6P (blood glucose) + gluconeogenic precursors = glycogen

Question 10

hexokinase type 1 and 2 location

Answer 10

muscle, brain, adipose tissue

Question 11

glucokinase (hexokinase type 4) location

Answer 11

liver and pancreas

Question 12

hexokinase inhibition

Answer 12

allosterically inhibited by G6P (its product)
when cell has enough G6P, glucose entry into cell is slowed

Question 13

glucokinase inhibition

Answer 13

not inhibited by G6P

Question 14

hexokinase Km

Answer 14

low Km
function at max velocity at fasting blood glucose concentrations

Question 15

glucokinase Km

Answer 15

high Km
functions at max velocity only when glucose levels are high (such as following a high-carbohydrate meal)

Question 16

hexokinase and insulin

Answer 16

not induced by insulin in normal individuals

Question 17

glucokinase and insulin in normal individuals

Answer 17

induced by insulin in normal individuals

Question 18

hexokinase and insulin in insulin-resistant individuals

Answer 18

not induced by insulin

Question 19

glucokinase and insulin in insulin-resistant individuals

Answer 19

not induced by insulin

Question 20

which form of glycogen synthase (dephosphorylated or phosphorylated) is more active

Answer 20

dephosphorylated
insulin promotes dephos

Question 21

what promotes dephosphorylation of glycogen synthase

Answer 21

insulin
this is how insulin stimulates glycogenesis

Question 22

what is induced by insulin?

Answer 22

glucokinase!

Question 23

what is an alternate source of glucose for glycogensis?

Answer 23

newly synthesized glucose from gluconeogenesis

Question 24

step 2 of glycogenesis

Answer 24

transfer phosphate from carbon 6 of glucose to carbon 1
enzyme: phosphoglucomutase

Question 25

step 3 of glycogenesis

Answer 25

uridine monophosphate combined with G1P to form UDP-glucose
energy from UTP to UMP (hydrolysis of anhydride bond)

Question 26

in what form is glucose incorporated into glycogen?

Answer 26

UDP-glucose

Question 27

step 4 of glycogenesis

Answer 27

UDP-glucose to glycogen
enzyme: glycogen synthase

Question 28

what does glycogen synthase require

Answer 28

preformed glycogen as a primer

Question 29

how is initial glycogen formed

Answer 29

glucose residue binds to glycogenin

Question 30

when is glycogen synthase active

Answer 30

when it is dephosphorylated

Question 31

when is glycogen synthase inactive

Answer 31

phosphorylated

Question 32

insulin and glycogen synthesis

Answer 32

insulin stimulates dephosphorylation of glycogen synthase (activates it)

Question 33

after 6 or 7 glucose molecules are added to glycogen chain,

Answer 33

branching of chain

Question 34

branching enzyme

Answer 34

transfers 6 or 7 glucoses to C-6-OH group
forms alpha(1-6) bonds bc glycogen synthase can’t

Question 35

why is branching important

Answer 35

increases molecule’s solubility and compactness
makes nonreducing ends of chains available so glucose can be cleaved rapidly and used for energy (glycogenolysis)

Question 36

glycogenesis energy use

Answer 36

consumes energy bc an ATP and UTP are consumed for each molecule of glucose introduced