Carbohydrate metabolism Flashcards
Four ways to regulate/modulate metabolic pathways
Substrate availability, allosteric activation/inhibition, covalent modification of enzyme, and induction/repression of enzyme synthesis
Two classes of glucose transporters
- Na+/glucose cotransporter
2. Facilitative glucose transporters
GLUT1 importance
Basal glucose uptake, housekeeping, very low Km - transports glucose from the lumen of intestine into the cell
GLUT2 importance
Very high Km, means that when blood sugar rises up then you are able to sense it
Two phases of glycolysis
Preparatory phase, pay-off phase
three steps that regulate glycolytic flux through pathway
Glucokinase, Phosphofructokinase, Acetyl-CoA PKA mediated Phos. Steps with the biggest changes in Gibbs free energy are those that are irreversible
PFK-1 is sensitive to energy levels in what way?
In presence of ATP it is less active, and in the presence of AMP it is more active
Major allosteric regulators for most of metabolic enzymes
ATP, ADP
warburg effect
cancer cells with perfectly functioning mitos that can choose to rely on glycolysis as major path of emitting ATP
two major shuttle systems for reducing equivalents into mito
glycerol 3-phosphate shuttle, malate-aspartate shuttle
goals of reducing equivalent shuttle systems (2)
- Transfer reducing equivalent in NADH to mitos
2. Generate NAD+ to keep glycolysis running under aerobic conditions
end result of glycolysis
production of pyruvate
what happens to pyruvate after glycolysis?
it can go into the TCA cycle (Mitos), or go into gluconeogenesis or lactic acid
pentose phosphate pathway generates
nucleic acids from 6 garbon glucose that you’ve eaten
two major functions of PPP
- Generate 5-carbon riboxe
2. Generates NADPH, needed for reducitve biosynthesis and recycling
Gatekeeper controlling how much Acetyl-CoA flows into TCA
Pyruvate dehydrogenase
three irreversible steps in TCA which are highly regulated
Citrate synthase, isocitrate dehydrogenase, and KDH (alpha-ketogluterate dehydrogenase)
two major roles of the TCA cycle
- Generate energy (ATP and NADH)
2. Provide substrates for biosynthetic process
what happens to glucose when it enters the cell?
PPP, glycolysis, TCA, gluconeogenesis
what are the building blocks of de novo generated glucose
amino acids and glycerol
what is the benefit to making glucose from scratch?
you need to maintain blood sugar within a narrow range
primary substrates for gluconeogenesis
amino acids, pyruvate, lactate, glycerol
atkins diet works by
carbohydrate starvation, so your liver is always turning on gluconeogenic pathways, requires the breakdown of free fatty acids leading to weight loss
where does gluconeogenesis happen?
80% in liver, 20% in kidney
