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