MEH - Metabolism and Exercise Flashcards by RG Cattermole

What two fuels are normally available in the blood for use?

Glucose (little free glucose - more glycogen stores)
Fatty acids (from triacylglycerol)

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What fuels are available under special conditions?

Amino acids
Ketone bodies
Lactate

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How is PFK regulated?

Hormonal - insulin stimulates

Allosteric - stimulated by high AMP

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How is TCA cycle regulated?

Stimulated by high ADP and NAD+

Inhibited by isocitrate dehydrogenase and NADH

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What is Fatty acid transport into mitochondria (carnitine shuttle) inhibited by?

Malonyl co A (intermediate in FA synthesis) Prevents newly synthesised FA from being immediately transported into mitochondria and oxidised

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Where are ketone bodies made?

Liver from acetyl co A

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When might you see ketone body formation?

Starvation

Diabetes - untreated

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What level should blood glucose be kept at?

3.6-6mmol/L

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What levels of glucose is hypoglycaemia?

<3mmol/L

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What are some symptoms of hypoglycaemia?

CNS problems
staggering
confusion
slurred speech
loss of consciousness
death

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How many g or kg store do we have of: Glycogen, fat, amino acid?

400g
10-15kg
6kg

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Where is glycogen made and stored?

Liver and muscle

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Which two hormones promote fuel storage and are therefore anabolic?

Insulin

Growth hormone

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Which 4 hormones promote fuel breakdown and are therefore catabolic?

Glucagon
Adrenaline
Cortisol
Thyroid

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Reduction of blood glucose stimulates what hormones? What do these hormones do?

Cortisol
Glucagon

Stimulate gluconeogenesis
Glycogenolysis

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Reduced insulin and effect of cortisol (inhibits insulin) stimulates what kind of fuel use?

Fatty acids

What two ways can fats be used to make energy in starvation? What happens when fat stores run out?

Glycerol - gluconeogenesis
Fatty acids - ketones

Need to break down proteins - ketogenic and glucogenic

How can loss of muscle mass in starvation lead to death?

Loss of respiratory muscles

Respiratory infection

Which 4 systems require adaptations during exercise?

Respiratory
Cardiovascular
Musculoskeletal
Temperature regulation

What does the metabolic response to excercise need to ensure it maintains?

Blood glucose to brain
Mobilise stores for fuel energy
Minimal disturbances to metabolic homeostasis but keep mobilisation equal to rate of utilisation
End products removed as quickly as possible

What are the first immediate sources of energy in exercise?

ATP - 2 seconds

Phosphocreatine - 5 seconds

What is the next source of energy? How is it used?

Glycogen - 2 mins in sprint or 1 hour of low intensity exercise

Glycolysis
Oxidative phosphorylation

What uses most of the ATP in muscles?

Myosin ATPase ~70%. Rest goes to other cellular processes like maintaining ionic gradients across the cell membrane.

How does adrenaline increase energy in exercise? Which enzyme?

Stimulates glycogenolysis

Glycogen phosphorylase

What is the principal organ for regulating blood glucose?

Liver

How does the liver increase glucose during exercise?

Glycogenolysis | Gluconeogensis

What is the cori cycle?

Liver recycles lactate from anaerobic metabolism and converts it to glucose

How does muscle take up glucose during exercise if theres no insulin promoting GLUT4 translocation to membrane?

There is an insulin independent process of glucose uptake (increased AMP stimulates AMPK resulting in signal cascade which increases GLUT4 translocation).

Why are fatty acids needed as fuel during prolonged excercise?

1) Liver doesn't produce enough glucose | 2) Need to maintain glucose levels for brain

Why is fatty acid metabolism slow?

Because it is limited by the carnitine shuttle Slow release from adipose tissue Low rate of ATP production but high capacity for sustained production

What are the problems with anaerobic metabolism?

Incomplete glucose metabolism Produces Lactate - reduces pH acidosis and fatigue Inefficient - only 2ATP

What fuel would a sprinter use for 100m?

Initial ATP and phosphocreatine then muscle glycogen

What fuel would a middle distance runner use?

60% aerobic 40% anaerobic Initial phosphocreatine and anaerobic glycogen metabolism Long middle phase aerobically from muscle glycogen Finish aerobic metabolism of glycogen --> lactate

What fuels would a marathon runner use?

95% aerobic Muscle glycogen Liver glycogen Fatty acids

How long does muscle glycogen stores last compared to liver glycogen? After how long does fatty acid fuel use occur in exercise?

Muscle - few minutes Liver - 1 hour 20-30mins fatty acid utilisation

How do hormones control the metabolic response to running a marathon?

Insulin - falls steadily (inhibited by adrenaline) Glucagon levels rise: Increased glycogenolysis (glycogen phosphorylase) Stimulates gluconeogenesis (PEPCK and fructose 1,6 bisphosphatase) Stimulates lipolysis (hormone sensitive lipase) Adrenaline and growth hormone rise rapidly Adrenaline stimulates glycogenolysis and lipolysis Growth hormone mobilised fatty acids (lipolysis) Cortisol rises slowly - stimulates gluconeogenesis and lipolysis

What are the benefits of exercise (6)? Star the ones that are important for diabetics

*Body composition changes - decreased fat increased muscle *Glucose tolerance improves - muscle glycogenesis *Insulin sensitivity of tissues increases *Blood triglycerides decrease *Blood pressure falls Psychological effects of well-being