TOPIC A/1: Glucose metabolism Flashcards
Define metabolism
the entire set of enzyme catalysed transformations of organic molecules in living cells
sum of anabolism and catabolism.
How are enzymes regulated by amount
Increasing or reducing the amount of active enzyme by lifespan, inducing/repressing, compartmentalisation
How are enzymes regulated by activity
Increasing or reducing the activity of an enzyme by concentration, allosteric modulation, phosphorylation and regulatory molecules
Outline hormone regulation
Hormones are released into bloodstream and bind to chemical receptors to elicit a cell response
Glycolysis
futile cycle 1
Hexokinase
Low G6P stops inhibition
Low F6P stops compartmentalisation
Gluconeogenesis
bypass reaction 3
G6Pase
no enzyme = no reaction
Glycolysis
futile cycle 2
Phosphofructokinase-1
Low ATP and citrate stops inhibition
High AMP, ADP and fructose 2,6-bisphosphate stops inhibition by ATP
Gluconeogenesis
bypass reaction 2
Fructose 1,6-bisphosphatase-1
Low AMP and Fructose 2,6-bisphosphate stops inhibition
Glycolysis
futile cycle 3
Pyruvate kinase
Low ATP, Acetyl-CoA, fatty acids and alanine stop inhibition
Low glucagon stops inhibition by phosphorylation
High fructose 1,6-bisphosphate activates
Gluconeogenesis
bypass reaction 1
Pyruvate carboxylase and PEP carboxykinase
Oxaloacetate intermediate
Basic glycogenesis - glycogenolysis pathway
Glucose
UDP-glucose Glycogen
Glucose 1-Phosphate
Glucose 6-Phosphate (enzyme only in liver)
muscle = Pyruvate,
liver = Glucose.
2 ways of regulating glycogenesis
Insulin signalling
Glycogen synthase regulation
Explain insulin signalling of glycogenesis
levels too high insulin secreted increased glucose transport to muscle increased muscle hexokinase activity activation of glycogen synthase
Explain glycogen synthase regulation of glycogenesis
dephosphorylation activates glycogen synthase (from b to a form)
dephosphorylation = PP1
phosphorylation = CKII and GSK3
Regulation of PP1 for glycogenesis
activated by:
insulin
glucose
G6P (allosteric binds to synthase increasing affinity for PP1)
inhibited by:
glucagon
epinephrine
Regulation of CK11 and GSK3
GSK3 inhibited by:
Insulin
2 ways of regulating glycogenolysis
glucagon/epinephrine signalling pathway (hormonal regulation)
glycogen phosphorylase regulation
What is the enzyme responsible for glycogenesis
glycogen synthase
What is the enzyme responsible for glycogenolysis
glycogen phosphorylase
Explain glycogen phosphorylase regulation of glycogenolysis
phosphorylation causes activation (less active b to a form)
phosphorylation = phosphorylase b kinase
dephosphorylation = PP1
regulation of phosphorylase b kinase
activated by:
glucagon in liver
epinephrine with Ca and AMP (allosteric) in muscle
regulation of PP1 for glycogenolysis
activated by:
glucose binding to phosphorylase a to expose phosphoryl groups
explain hormonal regulation of glycogenolysis
epinephrine in muscles
glucagon in liver
G6P in muscle into glycolysis
G6P in liver to glucose for blood glucose levels
glucagon and epinephrine both pathway regulation
activate glycogen phosphorylase, inhibit synthase
GLYCOGEN BREAKDOWN
