Lecture 304: glycogen and dietary sources of glucose

Question 1

pathways activated by insulin

Answer 1

• glycogenesis

- glycolysis

Question 2

pathways activated by glucagon

Answer 2

• gluconeogenesis

- glycogenolysis

Question 3

storage of glucose

Answer 3

• animals store glycogen

- plants store starch

Question 4

storage of glycogen is (un/ limited)

Answer 4

• limited!!

Question 5

glycogen stored in

Answer 5

• mostly skeletal muscles
• liver
• fat

Question 6

linkages that increase solubility of glycogen

Answer 6

alpha (1-6) linkages

Question 7

glycogenesis

Answer 7

• glycogen synthesis
• requires UTP [energy]
• activated by insulin [can come from glycolysis or gluconeogenesis]
• starting point is glucose-6-phosphate

Question 8

step 1

Answer 8

• G6P converted to G1P via phosphoglucomutase
• move phosphate group from C6 to C1
• reversible

Question 9

step 2

Answer 9

• convert G1P + UTP to UDP-Glc and pyrophosphate
• irreversible [costs 2 high energy bonds from UTP and pyrophosphate]
• side rxn of pyrophosphate pulls rxn forward to synthesis of G1Pase

Question 10

step 3

Answer 10

• glycogen primer via glycogenin
• glycogen biosynthesis starts on glycogenin protein itself [-OH group on tyrosine residue]
• via alpha (1-4) linkages
• UDP released

Question 11

step 4

Answer 11

• UDP-Glc + glycogen primer converted to glucose via glycogen synthase
• glycogen synthase and branching enzyme work together to form glycogen [~60,000 glucose polymers added]

Question 12

glycogenin

Answer 12

• only capable of making alpha (1-4) linkages

- starts glycogen biosynthesis

Question 13

glycogen phosphorylase

Answer 13

• cleaves (1-4) linkages = synthesis of G1P
• irreversible
• regulated

Question 14

polysaccharides

Answer 14

• glycogen

- starch

Question 15

carbohydrate digestion occurs in ___ and ___, but only ____ can absorb monosaccharides

Answer 15

• mouth and small intestine

- only small intestine can absorb monosaccharides

Question 16

alpha-amylase

Answer 16

• digests alpha (1-4) linkages

- end result is maltose

Question 17

isomaltase

Answer 17

• digests alpha (1-6) linkages

- end result is glucose

Question 18

lactose

Answer 18

• glucose + galactose via lactase

Question 19

sucrose

Answer 19

• glucose + fructose via sucrase

Question 20

maltose

Answer 20

• 2 glucose via maltase

Question 21

monosaccharides that can enter the cell

Answer 21

• all can enter the cell

Question 22

majority of linkages

Answer 22

alpha (1-4) linkages

Question 23

UDP-glucose

Answer 23

activated glucose

Question 24

intermediate of both glycolysis and glycogenesis

Answer 24

glucose-6-phosphate

Question 25

glycogen synthase

Answer 25

- synthesizes all additional (1-4) linkages - irreversible - regulated - requires UDP-glu

Question 26

branching enzyme

Answer 26

- synthesizes all of (1-6) linkages - allows multiple chains of (1-4) linkages - doesn't require UDP-glu

Question 27

debranching enzyme

Answer 27

- cleaves (1-6) linkages | - product = glucose

Question 28

brain can only transport

Answer 28

glucose

Question 29

metabolizes majority of ___ and ____

Answer 29

- galactose | - fructose