Flashcards in Exercise and Metabolism Deck (18):
Describe type I muscle fibres
these are slow twitch fibres develop tension slowly and use aerobic oxidative metabolism and are rich in mitochondria
Describe type II muscle fibres
fast twitch muscle uses anaerobic metabolism and the main fuel is muscle glycogen (and phosphocreatine)
How is muscle glycogen breakdown associated with calcium?
phosphorylase kinase a (PKA) is activates via a calcium binding subunit (calmodulin) which subsequently causes the enzyme to active glycogenphosphorylase enzyme which converts glycogen to glucose-1-phosphate
How is the pyruvate dehydrogenase complex controlled?
by phosphorylation which is conducted by PDH kinase which response to ATP and NADH levels, when phosphorylated it is inactive, when not it is active. When calcium is present as it is in muscle contraction, this binds to the PDH kinase and causes the removal of the phosphate to activate PDH to allow aerobic respiration more so
How is the pyruvate dehydrogenase complex affected by the presence of calcium?
The binding of calcium causes the PDH kinase to remove the phosphate group and activate the enzyme to encourage entry into the TCA cycle (oxidative metabolism)
What is glycogen phosphorylase activated by?
AMP levels and PFK1
Describe a mechanism present in the cardia which works to activate PFK1
High levels of AMP stimulate AMP kinase enzyme which activates the PFK2 enzyme which follows the normal conversion of glucose-6-phosphate to fructose-6-phosphate but then converts this fructose-6-phosphate to fructose-2,6-bisphosphate (instead of fructose 1,6-bisphosphate) which is a strong allosteric stimulator of the PFK1 enzyme to encourage glycolysis
What facilitates the shift from glucose to fatty acid metabolism in prolonged exercise?
Describe how AMP kinase works to lower malonyl-CoA concentrations and increased fatty acid oxidation
AMPK phosphorylates acetyl CoA carboxylase which in turn activates the carnitine shuttle involved in transporting fatty acids into the mitochondrial for breakdown. Malonyl CoA is usually produced in fatty acid synthesis and is an inhibitor of the carnitine shuttle and therefore fatty acid synthesis is inhibited to stop this
Outline the metabolic adaptation occurring during fatigue
running out of glycogen, depletion of phosphocreatine, excessive rates of glycogen to lactic acid conversion which inhibits glycolysis and oxidative phosphorylation and there may be insufficient, inflexible or inefficient mitochondria.
What fuel does the brain use for respiration?
glucose predominantly, but if there is a shortage will use a combination of glucose and keto acids
What is ethanol metabolised to in the body?
Where does alcohol detoxification occur?
Describe the ways in which ethanol can be metabolised.
Cytosolic alcohol dehydrogenase pathway - main pathway where alcohol dehydrogenase enzyme produces NADH and H+ products alongside acetaldehyde.
Microsomal ethanol oxidising system - cytochrome p450 enzyme in SER
What happens after acetaldehyde is formed in the metabolism of alcohol?
It enters the mitochondria of the liver cell for further oxidation by aldehyde dehydrogenase to become acetate which is generally exported out of the liver for metabolism by other tissues
How does alcohol metabolism affect metabolism of carbohydrates and fats?
Fate of acetate depends on NADH:NAD+ ratio, and as alcohol dehydrogenase and aldehyde dehydrogenase consume NAD+ this causes a higher ration which inhibits the TCA cycle (it inhibits the malate shuttle) and inhibits gluconeogenesis (affects dehydrogenase reactions)
What is the role of glycogen phosphorylase?
break down glycogen to glucose-1-phosphate