L18: Glucose homeostasis Flashcards
role of glucose
source of energy
required for synthetic reactions
pentose phosphate pathway
advantages of glucose
water soluble
can cross BBB
oxidised anaerobically
disadvantages of glucose
low yield of ATO
osmotically actice
high conc- can damage cells
sources of blood glucose
- diet
- liver glycogen
- liver gluconeogenesis
role of glycogen in the liver
maintain blood glucose under control of insulin and glucagon
what is muscle sensitive to?
adrenaline, calcium, AMP, ATP
Product of glycogen synthesis - ‘activation’ of glucose
UDP GLUCOSE
product of glycogen breakdown
glucose + Pi
2 controls in the pathway of regulation of glucose metabolism
Allosteric control, hormonal control
regulation of glycogen metabolism by glucagon/ adrenaline and function of hormones
hormone binds cell surface receptor & activates internal signalling pathway that activates protein kinase
gluconeogenesis
glucose is synthesised from non-carbs sources in the liver
which sources can glucose be synthesised from during gluconeogenesis
- lactate
- glycogenic amino acids
- glycerol
why can’t glucose be synthesised from free fatty acids
pyruvare dehydrogenase is irreversible
what are the irreversible reactions in glycosis catalysed by?
- hexokinase/glucokinase
- phosphofructokinase
- pyruvate kinase
what enzymes are involved in the reversal of hexokinase & phosphofructokinase reactions ?
glucose-6-phosphatase
fructose 1,6-biphosphatase
2 steps of reversal of pyruvate kinase reaction
- pyruvate carboxylated in pyruvate carboxylate, yielding oxaloacetate, requiring ATP
- oxaloacetate converted into PEP by PEP carboxykinase, requiring GTP which releases CO2
what does pyruvate carboxylase reaction allow of glucose
Regeneration of glucose from pyruvate
describe the ‘cori cycle’
lactate from muscle is converted to glucose in the liver, and glucose is returned to muscle and used in glycolysis
what enzyme converts lactate to pyruvate?
lactate dehydrogenase
role of blood glucose maintenance
maintain physiological blood glucose concs needed to preserve function of brain & other tissues dependent on glucose
role of insulin, glucagon, glucose and adrenaline in blood glucose maintenance
signal & coordinate activities of liver, adipose tissue, muscle tissue
Is insulin a anabolic/catabolic hormone
anabolic
is glucagon an anabolic/catabolic hormone
catabolic
define anabolic pathway
requires energy; build up large molecules from smaller ones
define catabolic pathway
releases energy; break down large molecules into smaller ones
what does insulin promote
promote synthesis & storage
what does glucagon promote?
promotes degradation of stored fuel
metabolic effects of insulin in liver
- activates glycogen synthesis
- increase amino acid uptake
- increase fatty acid synthesis
- inhibits gluconeogenesis
metabolic effects of insulin in muscle
- activates glycogen synthesis
- increase amino acid uptake
metabolic effects of glucagon
- increase in blood glucose
- increase in circulating fatty acids & ketone bodies
- decrease in plasma amino acids
