Outline of what this flashcard set covers (in red)
What is Hypoglycaemia?
Low blood glucose levels
What is Hyperglycaemia?
High blood glucose levels
What are the symptoms of Hypoglycaemia? (8)
Shakiness or tremors
Sweating
Irritability or mood changes
Loss of coordination
Rapid heartbeat
Blurred vision
Weakness or fatigue
Severe cases may lead to Hypoglycaemic coma and death
What are the symptoms of Hyperglycaemia? (8)
Increased thirst (polydipsia)
Frequent urination (polyuria)
Fatigue
Blurred vision
Slow wound healing
Increased hunger (polyphagia)
Non-enzymatic modification of proteins
Severe cases may lead to Hyperosmolar coma
What is the value when blood glucose is considered critically low?
2.5mM
Picture overview of the processes that occur in the Liver
Where does glycogenesis take place?
-Liver (100g)
-skeletal muscle (300-400g)
When does glycogenesis take place?
When blood glucose levels are high
Why does glycogenesis take place?
Glycogen is a safe way to store glucose
What regulates glycogen synthesis?
Insulin
What bonds does glycogen have?
-alpha-1,4-glycosidic bonds
-alpha-1,6-glycosidic bonds
Outline the steps of glycogen synthesis:
What does the branching enzyme do in glycogen synthesis?
-The branching enzyme transfers a segment of the growing chain and attaches it to an earlier part of the chain
-Forming an alpha-1,6-glycosidic bond
Why does the body store glucose in the form of glycogen? (3)
• Cannot store glucose as it is osmotically active
• 400mM glucose is stored as 0.01μM glycogen, so storage efficient
• The branched structure of glycogen means it can be rapidly mobilised
Glycogen synthesis requires a protein primer called what?
Glycogenin
Glucose is activated by the reaction with...?
UTP (Uridine triphosphate)
What enzyme forms the alpha 1-4 glycosidic bonds?
Glycogen synthase
What are the FOUR things that stimulate glycogenolysis (breakdown)?
-Glucagon
-Adrenalin
-Noradrenaline
-Growth hormone
Picture outlining the steps in glycogen breakdown:
Glycogenolysis yields two products, what are they?
-Glucose 1-phosphate
-Glucose
Three enzymes are required for glycogenolysis; What are these enzymes?
-Phosphorylase
-Transferase
-Debranching enzyme
What does phosphorylase do in glycogenolysis?
Breaks the a1-4 links
What does transferase do in glycogenolysis?
Moves 3 glucose residues to an existing chain
What does Debranching enzyme a1-6 do in glycogenolysis?
Hydrolyses the remaining alpha-1,6-glycosidic bond at the branch point
Phosphoglucomutase converts what into what?
Converts G1P to G6P
Glucose 6 phosphatase converts G6P to glucose in the liver and kidney, but not in...?
Muscle
What is Glycogen Phosphorylase? Role?
An enzyme involved in glycogenolysis, the breakdown of glycogen into glucose
How is Glycogen Phosphorylase regulated?
• By allosteric interactions that signal the energy state of the cell
• Also by reversible phosphorylation regulated by hormones such as insulin, glucagon, adrenalin and noradrenalin
• Regulation of glycogen phosphorylase differs in muscle and liver
What converts Glycogen phosphorylase b (inactive) to Glycogen phosphorylase a (active)?
Phosphorylase b kinase
Outline the steps in the conversion of Glycogen phosphorylase b (inactive) to Glycogen phosphorylase a (active)?
When does 5'-AMP form?
When ATP is depleted
In muscle, glycogen phosphorylase b can be activated by 5'-AMP without undergoing what?
Phosphorylation
5'-AMP is a good indicator of what?
Low ATP energy levels
ATP, which is abundant when energy levels are sufficient, competes with 5'-AMP for the same binding site on glycogen phosphorylase. When ATP binds what is prevented?
Prevents unnecessary glycogen breakdown when energy stores are adequate.
In the liver, glycogen phosphorylase exists in what form?
Phosphorylase a
When glucose is generated due to ATP, glucose inhbits a molecule; What is this molecule? Why?
-Activated phosphorylase kinase a in the liver
-Feedback inhibition prevents excessive glycogen breakdown when glucose levels are sufficient
Ca2+ ions activate what?
Phosphorylase b kinase
-In muscle, mediating glycogenolysis during muscle contraction
In the liver, a-adrenergic activation stimulates what?
Ca2+ release
When is Glycogen synthase activated and what is it stimulated by?
-Activated in times of plenty of glucose
-Stimulated by Insulin
When is Glycogen phosphorylase activated and what is it stimulated by?
-Activated when blood glucose is low
-Stimulated by Glucagon, Adrenaline and noradrenaline
What specific molecules activate and inactivate Glycogen synthase? (3)
– Activated by ATP and G6P
– Inactivated by phosphorylation (by protein kinase A)
– Activated by dephosphorylation (by protein phosphatase-1)
What specific molecules activate and inactivate Glycogen phosphorylase?
– Inactivated by ATP and G6P
– Activated by phosphorylation (by phosphorylase b kinase
– Inactivated by dephosphorylation (by protein phosphatase-1)
Outline the steps in the Pentose Phosphate Pathway:
What is Gluconeogenesis?
A metabolic pathway that involves the synthesis of glucose from non-carbohydrate precursors.
Where does Gluconeogenesis take place?
-60% in the liver
-40% in the kidney
-Small amount in the intestine
When does Gluconeogenesis take place?
-When blood glucose levels are low fasting, starvation
Outline the steps of gluconeogenesis: (HINT: Kind of the reverse of glycolysis)
Outline the steps of gluconeogenesis at the membrane of cells (diagram answer)
Three most important substrates for gluconeogenesis are what?
-Amino acid (alanine)
-Lactate
-Glycerol (from triglycerides)
What is the daily requirement of glucose in the body? How much does your brain need?
-Daily requirement is 160g
-The brain needs 120g
What is the total body reserves of glucose at any given time?
210g