008 TCA Cycle and Organ Specific Shuttles Flashcards
other names for TCA
Tricarboxylic acid cycle (TCA)
citric acid cycle
krebs cycle
this cycle is amphibolic
meaning it has both catabolism and anabolism in the pathway
function of TCA cycle
oxidizing carbon fuels for harvesting high energy electrons
source of precursors for biosynthesis
takes place in the mitochondria
precursors of acetyl CoA
fats/LIPIDS (fatty acids and glycerol) polysaccharides/CARBS (glucose, other sugars) --> pyruvate PROTEINS (AA) essential amino acids ethanol acetic acid
three energy equivalent substances
NADH
FADH2
GTP
acetyl CoA
activated form of acetate
high energy bond embedded in thirster group
delta G= -7.5 kcal/mole
this catalyzes the decarboxylation of pyruvate into Acetyl CoA
pyruvate dehydrogenase complex (PDC)
this happens in the mitochondria using the pyruvate mitochondrial carrier (PMC)
steps 1 and 2
condensation and isomerization to generate isocitrate
step 3 and 4
irreversible oxidation and decarboxylations (NADH, CO2, and Succinyl CoA)
step 5
formation of succinate and GTP
steps 6-8
produce FADH2, NADH, and regenerate oxaloacetate
which steps are regulated and irreversible
steps 1,3, and 4
in a phosphate deficiency, PDC is always in
phosphorylated form (inactive)
glucose—>lactate rather than acetyl coA
results in lactic acidosis (high levels in blood of lactic acid)
central nervous system affected the most
when cellular ATP levels are low, activity of TCA is
increased
high cellular levels of ATP triggers the
inhibition mechanism of TCA cycle (mitochondrial ETC inhibition)
reactions that provides intermediates for pathways
anaplerotic reactions
two major anaplerotic reactions
- degradation of amino acids
2. carboxylation of pyruvate
molecules used in metabolic processes takes place in the mitochondria. they can penetrate the outer membrane but
cannot penetrate the inner membrane, require a shuttle system to cross. this is more regulated
reduced NADH cannot cross the mitochondrial membrane, so there are two shuttle systems
- malate-aspartate shuttle
2. glycerophosphate shuttle
malate-aspartate shuttle
operates in heart, liver and kidneys (energy consuming organs that work really hard)
generates reduced NADH in mito-matrix
reduced NADH enters ETC at Complex-1
glycerophosphate shuttle
operates in skeletal muscle and brain (instant energy, need it now!)
Generates reduced FADH2 in the inner mito membrane
reduced FADH2 joins to ETC at CoQ
