Metabolism 2

Question 1

glycolysis: which is the most important step?

Answer 1

the one catalyzed by PFK-1: allosteric enzyme (F6P to F16BP)

Question 2

glycolysis: penultimate product? regulates?

Answer 2

PEP - allosteric inhibitor of PFK-1 via feedback inhibition

Question 3

hormonal regulation of glycolysis: direct? how?

Answer 3

indirect: via PFK-2 that makes F26BP instead of F16BP

Question 4

PFK-2’s actions of PFK-1?

Answer 4

ACTIVATES PFK-1 allosterically

Question 5

how is PFK2 regulated?

Answer 5

insulin stimulates PFK2 (so stimulates glycolysis). glucagon inhibits PFK2 (so inhibits glycolysis)

Question 6

glycogen: definition? stored where?

Answer 6

polymer of glucose molecules which are linked by glycosidic bonds (less reactive than glucose, 1-OH inactivated). stored in liver, cardiac and skeletal muscle.

Question 7

glycogen metabolism in the liver: fed vs. fasted state?

Answer 7

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

Question 8

glycogen metabolism in skeletal/cardiac muscle: fed vs. fasted state?

Answer 8

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

Question 9

first step of glycogen synthesis is also?

Answer 9

also the first reaction of glycolysis: glucose to G6P then can be catabolized to pyruvate or stored as glycogen

Question 10

glycogen synthesis: RLS?

Answer 10

glycogen synthase; last step to make glycogen

Question 11

glycogen breakdown: RLS? then next step?

Answer 11

glycogen phosphorylase. in muscle: glycolysis: converted into glucose via G6Pase then exported. muscle: glycolysis. since it doesn’t have G6Pase

Question 12

hormonal regulation of glycogen metabolism: liver?

Answer 12

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.

Question 13

skeletal and cardiac muscle: hormonal regulation of glycogen metabolism

Answer 13

insulin: activates phosphatases so activates glycogen synthase, inhibits glycogen phosphorylase = glucose is stored. glucagon: muscle cells don’t have glucagon receptors, don’t respond.

Question 14

gluconeogenesis? what? where? catabolic or anabolic? opposite of?

Answer 14

synthesizes glucose. almost exclusively in liver. anabolic: reverse of glycolysis

Question 15

why is liver the only gluconeogenic organ?

Answer 15

glucose 6 phosphate is only found in the liver (converts G6P to glucose) so only liver can complete gluconeogenesis

Question 16

gluconeogenesis regulated ___ with ___?

Answer 16

reciprocally with glycolysis.

Question 17

gluconeogensesis regulation: what does insulin do? results?

Answer 17

insulin activates PFK2, increases F26BP, which inhibits F16BPase (gluconeogenesis) and activates PFK 1 (glycolysis)

Question 18

adipocytes: ability to synthesize TAGs? depends on?

Answer 18

unlimited ability to synthesize and store TAGs: only depends on supply of FAs and glycerols

Question 19

Why do we have fat?

Answer 19

more efficient store of energy than carbohydrate; twice calories per gram; also excludes water since it’s non-polar and hydrophobic = 6X more effective

Question 20

TAG synthesis: regulation? breakdown of TAGs also called? regulation?

Answer 20

not regulated; only depends on supply. lipolysis - regulated via hormone sensitive lipase

Question 21

catabolism of fatty acids: also called? two major sites?

Answer 21

beta-oxidation. liver (make ketone bodies) and skeletal muscle (to make its own ATP).

Question 22

fatty acids are delivered from ____ (in what form). cross cell membrane via ____. then transported where in what form?

Answer 22

delivered from blood bound to serum proteins; cross via passive transporter proteins. transported into mitochondrial matrix as acyl coA