Fuel Metabolism

Updated 2008-11-12 02:17


Question Answer
GLUT4insulin sensitive glucose transporter found on muscle and adipose tissue
Cori cycleexchange of glucose from liver for lactate from muscle
glucose-alanine cycleused to transfer nitrogen from muscle to liver
G6Pglucose 6 phosphate, liver uptakes glucose by converting it to G6P
glucokinaseenzyme that catalyses creation of G6P; activity increases with blood [glucose]
Acetyl CoA isEnd product of carbohydrate, AA and fat breakdown; goes into citric acid cycle to give H2O and CO2, or can produce fatty acids, or can produce ketone bodies
Ketone bodyalternative product of Acetyl CoA; can be used as energy by brain or muscle


Question Answer
<1 SecAllosteric activation, inhibition, competetive inhibition
secs to minsActivation of precursor proteins, activation/ inactivation by reversible covalent modification
mins to hoursSynthesis of new protein in response to signals (eg hormones)
days to weeksMajor changes to overall protein profile of a tissue (eg in response to diet & exercise), rebalancing of synthesis & breakdown
End product of carbohydrate, AA and fat breakdown isAcetyl CoA


Question Answer
fates of G6P?1. converted to glucose 2. converted to glycogen 3. converted to acetyl CoA, 4.degraded via pentose phosphate pathway to generate NADPH for biosynthesis of fatty acids
insuluin release is triggered byhigh blood glucose
insulin is produced bybeta cells of pancreas
Insulin's effect on muscleincreases glucose uptake, increases glycogen synthesis
Insulin's effect on adiposeincreases glucose uptake, increases lipogenesis, decreases lipolysis
Insulin's effect on liverincreases glycogen synthesis, increases lipogenesis, decreases gluconeogensis
Glucagon's effect on muscleno effect
Glucagon's effect on adiposeincreases lipolysis
Glucagon's effect on liverdecreases glycogen synthesis, increases glycogenlysis
Epinephrine's effect on muscleincreases glycogenlysis
Epinephrine's effect on adiposeincreases lipolysis
Epinephrine's effect on liverdecreases glycogen synthesis, increases glycogenlysis, increases gluconeogenesis
Epinephrine's effect on pancreasrelease of flucagon
Epinephrine binding to beta-adrenoreceptor on liver and muscle results inincreased intracellular cAMP, which leads to glycogen breakdown and gluconeogenesis
Epinephrine's binding to alpha-adrenoreceptor on liver works viaIP3 to increase intracellular Ca2+ which reinforces cell's response to cAMP
Epinephrine's binding to alpha and beta-adrenoreceptor on adipose leads toactivation of lipase which mobilises fatty acids

Signalling pathways

Question Answer
three major signal transduction pathways1. receptor tyrosine kinases with Ras signalling cascade 2. adenylate cyclase generates cAMP as a second messenger 3.phosphoinositide cleavage by phospholipase C (PLC) with inositol-1,4,5-trisphosphate(IP3) and 1,2-diacylglycerol (DAG) as well as Ca2+ as second messengers