Flashcards in Biochemistry Deck (74)
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1
What is glycogenesis?
Synthesis of glycogen from glucose
2
What is glycogenolysis?
Breakdown of glycogen to form glucose
3
Glycogenolysis occurs by hydrolysis. True/False?
False
Occurs by phosphorolysis
4
Where is glycogen stored in the body?
Liver
Muscle cells
5
What is the role of muscle glycogen?
Not used to maintain blood glucose; provides energy via glycolysis and TCA cycle during physical activity
6
Which bonds link glucose molecules to form glycogen?
Alpha-1,4-glycosidic bonds
7
Which bonds create branches in the glycogen chain?
Alpha-1,6-glycosidic bonds
8
Glycogen formation can be started by two glucose monomers joining together. True/False?
False
Glucose residues can only be added to an existing glycogen chain
9
What is required to begin glycogen formation?
Glycogenin
10
What is Glycogenin?
A glycogen primer containing 4 glucose monomers
11
Which enzyme effectively adds glucose monomers to Glycogenin to produce glycogen?
Glycogen synthase
12
When enough glucose is present, glycogen synthesis begins: glucose-6-phosphate is converted to what?
Glucose-1-phosphate
13
What is formed from glucose-1-phosphate in glycogen synthesis?
UDP-glucose
14
What is UDP-glucose?
Essentially an active form of glucose
15
Glycogen synthase adds only one glucose at a time to UDP-glucose to ultimately form glycogen. True/False?
True
16
How often are branches introduced into the glycogen chain?
Every 10 glucose molecules
17
When does glycogenolysis occur?
Between meals to maintain blood glucose levels
18
Which enzyme catalyses glycogenolysis?
Glycogen phosphorylase
19
Glycogen phosphorylase cleaves off only one glucose at a time from glycogen. True/False?
True
20
What are the 2 regulatory actions of insulin upon glycogen synthesis?
Stimulates glycogen synthesis
Inhibits glycogen phosphorylase
21
What are the 2 regulatory actions of glucagon upon glycogenolysis?
Stimulates glycogen breakdown
Inhibits glycogen synthase
22
What is gluconeogenesis? When does it occur?
Synthesis of glucose from non-carbohydrate precursors
Occurs when glycogen stores are completely depleted
23
Where does gluconeogenesis mainly occur?
Liver
24
Name the 3 main precursors for gluconeogenesis
Lactate (lactic acid)
Amino acids
Glycerol
25
Which TCA cycle intermediate is needed for gluconeogenesis? Why is it needed?
Oxaloacetate (4C)
Accepts acetyl groups from fat breakdown
26
Describe the Cori Cycle
Blood transports lactate to liver
Liver converts lactate to glucose
Glucose is released into blood
27
Which type of amino acids can be used to synthesise new glucose?
Glucogenic amino acids
28
Which type of amino acids cannot be used to synthesise new glucose?
Ketogenic amino acids
29
What effect do insulin and glucagon have on gluconeogenesis?
Insulin inhibits gluconeogenesis
Glucagon stimulates gluconeogenesis
30
