Integration of Metabolism Flashcards
why is energy intake sporadic
people eat different amounts of food everyday at different intervals
brain metabolic features
continuous high ATP requirement
glucose + some ketone bodies e.g. beta-hydroxybutyrate
cant use fatty acids
ketone body metabolism not as effective
hypo vs hyperglycaemia on the brain
hypo = faintness/coma
hyper = irreversible brain damage
light exercise muscle metabolism (when O2 not limiting)
oxidative phosphorylation
fat breakdown
ketone body oxidation
vigorous exercise muscle metabolism (when O2 limiting)
glycogenolysis
lactate formation (for glycolysis to continue)
heart metabolic features
constant atp requirement
fully aerobic using TCA substrates like FFAs and KBs
liver metabolic features
high metabolic activity
interconverts nutrient types
maintains blood glucose 4.0mM - 5.5mM
stores glucose as glycogen + key role in lipoprotein metabolism
what is gluconeogenesis essentially
glucose made from pyruvate
what enzymes need to be bypassed + why
hexokinase, phosphofructokinase + pyruvate kinase
reversal of their actions normally is energetically unfavourable (delta G = -90kJ/mol)
what enzymes are used to bypass in gluconeogenesis
mitochondria: pyruvate carboxylase
cytosol: phosphoenolpyruvate carboxylase, F-1,6-biphosphatase + G6-phosphatase
energetically favourable: -38kJ/mol
fats as fuel sources
FA: A-CoA (TCA) + KB (brain)
G: DHAP => gluconeogenesis
controlling metabolic pathways
earlier = more control
occurs at irreversible steps
by product inhibition of enzymes, signalling molecules
michaelis constant (Km)
concentration of substrate when enzyme function is half the maximal rate (Vmax)
hexokinase 1
in muscle
low Km - 0.1mM
active at low concs of glucose so even when glucose is low, still making ATP via glycolysis
inhibited by glucose-6-phosphate
irreversible
hexokinase 4
in liver
high Km - 0.4mM
active only on high concs of glucose
not inhibited by G6P
glucose-6-phosphatase used to reverse
