MEH - Metabolism and Exercise Flashcards
What two fuels are normally available in the blood for use?
Glucose (little free glucose - more glycogen stores) Fatty acids (from triacylglycerol)
What fuels are available under special conditions?
Amino acids
Ketone bodies
Lactate
How is PFK regulated?
Hormonal - insulin stimulates
Allosteric - stimulated by high AMP
How is TCA cycle regulated?
Stimulated by high ADP and NAD+
Inhibited by isocitrate dehydrogenase and NADH
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
Where are ketone bodies made?
Liver from acetyl co A
When might you see ketone body formation?
Starvation
Diabetes - untreated
What level should blood glucose be kept at?
3.6-6mmol/L
What levels of glucose is hypoglycaemia?
<3mmol/L
What are some symptoms of hypoglycaemia?
CNS problems staggering confusion slurred speech loss of consciousness death
How many g or kg store do we have of: Glycogen, fat, amino acid?
400g
10-15kg
6kg
Where is glycogen made and stored?
Liver and muscle
Which two hormones promote fuel storage and are therefore anabolic?
Insulin
Growth hormone
Which 4 hormones promote fuel breakdown and are therefore catabolic?
Glucagon
Adrenaline
Cortisol
Thyroid
Reduction of blood glucose stimulates what hormones? What do these hormones do?
Cortisol
Glucagon
Stimulate gluconeogenesis
Glycogenolysis
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
