Carbohydrate Metabolism Glycogen and Gluconeogenesis

Question 1

Glycogenesis

Answer 1

synthesis of glycogen from glucose monomers

Question 2

Glycogenolysis

Answer 2

breakdown of glycogen to form glucose monomers

Question 3

what is glycogen

Answer 3

main storage form of glucose in liver and muscle cells

Question 4

what types of links make straight chains and branches in glycogen
how is glycogen packaged within cells

Answer 4

straight chains - alpha 1-4 glycosidic links
branches - alpha 1-6 glycosidic links
packaged in granules

Question 5

how many glucose residues make up a glycogen primer

Answer 5

at least 4

Question 6

what protein attaches to a glycogen primer

Answer 6

glycogenin

Question 7

when making glycogen, what is made to prevent glucose-6-phosphate from entering glycolysis
what enzyme does this

Answer 7

glucose-1-phosphate
phosphoglucomutase

Question 8

what is UDP-glucose

Answer 8

an activated form of glucose (activated intermediate)

Question 9

what is the difference between liver glycogen and muscle glycogen roles

Answer 9

depends on the enzymes present in either tissue
liver - broken down between meals and released into the blood to maintain blood glucose levels
muscle - not able to be released into the blood, broken down to provide energy for that muscle cell during short bursts

Question 10

glucose-1-phosphate -> UDP-glucose enzyme
side product

Answer 10

UDP-glucose pyrophosphorylase
pyrophosphate ion

Question 11

UDP-glucose -> glycogen enzyme
side product

Answer 11

glycogen synthase
UDP

Question 12

where is energy stored in nucleotides

Answer 12

the phosphate ester linkage

Question 13

what happens to pyrophosphate when it is released
why is this important

Answer 13

it is hydrolysed by pyrophosphatase to 2 inorganic phosphate
drives the reaction in the forward direction towards UDP-glucose synthesis

Question 14

what is the rate-limiting enzyme of glycogenesis

Answer 14

glycogen synthase

Question 15

which enzyme extends existing branches of glycogen
which enzyme introduces branches to glycogen

Answer 15

glycogen synthase
transglycosylase

Question 16

how often does transglycosylase introduce alpha 1-6 glycosidic branches to glycogen

Answer 16

approx. every 10 glucose residues

Question 17

what hormone acts when blood glucose is higher than normal
what cells secrete it

Answer 17

insulin
pancreatic beta cells

Question 18

what hormone acts when blood glucose is lower than normal
what cells secrete it

Answer 18

glucagon
pancreatic alpha cells

Question 19

glycogen -> glucose-1-phosphate enzyme

Answer 19

glycogen phosphorylase

Question 20

what is the rate-limiting enzyme of glycogenolysis

Answer 20

glycogen phosphorylase

Question 21

why does glycogenolysis require an inorganic phosphate

Answer 21

glycogen phosphorylase uses Pi to make glucose-1-phosphate

Question 22

why can liver glucose-6-phosphate be made into glucose and released into the bloodstream but muscle glucose-6-phosphate cannot

Answer 22

in the liver, different enzymes are present so it can be dephosphorylated

Question 23

what is gluconeogenesis

Answer 23

synthesis of glucose within the body from non-carbohydrate precursors

Question 24

what are the precursors to glucose in gluconeogenesis

Answer 24

lactate
amino acids
glycerol

Question 25

why does gluconeogenesis require energy?

Answer 25

it requires the addition of phosphates

Question 26

how many unique enzymes are involved in gluconeogenesis (ie how many that are not also involved in glycolysis)

Answer 26

4

Question 27

what type of reaction is gluconeogenesis

Answer 27

anaplerotic

Question 28

what type of amino acids can be used in gluconeogenesis

Answer 28

glucogenic

Question 29

what type of amino acids cannot be used in gluconeogenesis

Answer 29

ketogenic