Lecture 304: glycogen and dietary sources of glucose Flashcards
1
Q
pathways activated by insulin
A
- glycogenesis
- glycolysis
2
Q
pathways activated by glucagon
A
- gluconeogenesis
- glycogenolysis
3
Q
storage of glucose
A
- animals store glycogen
- plants store starch
4
Q
storage of glycogen is (un/ limited)
A
- limited!!
5
Q
glycogen stored in
A
- mostly skeletal muscles
- liver
- fat
6
Q
linkages that increase solubility of glycogen
A
alpha (1-6) linkages
7
Q
glycogenesis
A
- glycogen synthesis
- requires UTP [energy]
- activated by insulin [can come from glycolysis or gluconeogenesis]
- starting point is glucose-6-phosphate
8
Q
step 1
A
- G6P converted to G1P via phosphoglucomutase
- move phosphate group from C6 to C1
- reversible
9
Q
step 2
A
- 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
10
Q
step 3
A
- glycogen primer via glycogenin
- glycogen biosynthesis starts on glycogenin protein itself [-OH group on tyrosine residue]
- via alpha (1-4) linkages
- UDP released
11
Q
step 4
A
- 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]
12
Q
glycogenin
A
- only capable of making alpha (1-4) linkages
- starts glycogen biosynthesis
13
Q
glycogen phosphorylase
A
- cleaves (1-4) linkages = synthesis of G1P
- irreversible
- regulated
14
Q
polysaccharides
A
- glycogen
- starch
15
Q
carbohydrate digestion occurs in ___ and ___, but only ____ can absorb monosaccharides
A
- mouth and small intestine
- only small intestine can absorb monosaccharides
