Metabolism 2 Flashcards
glycolysis: which is the most important step?
the one catalyzed by PFK-1: allosteric enzyme (F6P to F16BP)
glycolysis: penultimate product? regulates?
PEP - allosteric inhibitor of PFK-1 via feedback inhibition
hormonal regulation of glycolysis: direct? how?
indirect: via PFK-2 that makes F26BP instead of F16BP
PFK-2’s actions of PFK-1?
ACTIVATES PFK-1 allosterically
how is PFK2 regulated?
insulin stimulates PFK2 (so stimulates glycolysis). glucagon inhibits PFK2 (so inhibits glycolysis)
glycogen: definition? stored where?
polymer of glucose molecules which are linked by glycosidic bonds (less reactive than glucose, 1-OH inactivated). stored in liver, cardiac and skeletal muscle.
glycogen metabolism in the liver: fed vs. fasted state?
fed: glucose taken from blood into liver cells and stored as glycogen. fasted: liver breaks down its glycogen stores and releases glucose into blood stream for other tissues to use
glycogen metabolism in skeletal/cardiac muscle: fed vs. fasted state?
fed: glucose taken from blood stream into muscle cells, stored as glycogen. fasted (exercise): skeletal muscle uses glycogen stores to provide glucose for ATP production via glycolysis
first step of glycogen synthesis is also?
also the first reaction of glycolysis: glucose to G6P then can be catabolized to pyruvate or stored as glycogen
glycogen synthesis: RLS?
glycogen synthase; last step to make glycogen
glycogen breakdown: RLS? then next step?
glycogen phosphorylase. in muscle: glycolysis: converted into glucose via G6Pase then exported. muscle: glycolysis. since it doesn’t have G6Pase
hormonal regulation of glycogen metabolism: liver?
insulin (fed signal) activates phosphatases, dephosphorylate glycogen synthase (Activate) and glycogen phosphorylase (inhibit) = glucose is stored. glucagon activates kinases, so inhibits glycogen synthase and activates phosphorylase = glucose is released.
skeletal and cardiac muscle: hormonal regulation of glycogen metabolism
insulin: activates phosphatases so activates glycogen synthase, inhibits glycogen phosphorylase = glucose is stored. glucagon: muscle cells don’t have glucagon receptors, don’t respond.
gluconeogenesis? what? where? catabolic or anabolic? opposite of?
synthesizes glucose. almost exclusively in liver. anabolic: reverse of glycolysis
why is liver the only gluconeogenic organ?
glucose 6 phosphate is only found in the liver (converts G6P to glucose) so only liver can complete gluconeogenesis
gluconeogenesis regulated ___ with ___?
reciprocally with glycolysis.
gluconeogensesis regulation: what does insulin do? results?
insulin activates PFK2, increases F26BP, which inhibits F16BPase (gluconeogenesis) and activates PFK 1 (glycolysis)
adipocytes: ability to synthesize TAGs? depends on?
unlimited ability to synthesize and store TAGs: only depends on supply of FAs and glycerols
Why do we have fat?
more efficient store of energy than carbohydrate; twice calories per gram; also excludes water since it’s non-polar and hydrophobic = 6X more effective
TAG synthesis: regulation? breakdown of TAGs also called? regulation?
not regulated; only depends on supply. lipolysis - regulated via hormone sensitive lipase
catabolism of fatty acids: also called? two major sites?
beta-oxidation. liver (make ketone bodies) and skeletal muscle (to make its own ATP).
fatty acids are delivered from ____ (in what form). cross cell membrane via ____. then transported where in what form?
delivered from blood bound to serum proteins; cross via passive transporter proteins. transported into mitochondrial matrix as acyl coA
