B2.043 Metabolism and its Regulation Pt. 2

Question 1

how can metabolic plasticity be altered?

Answer 1

suppressed by over consumption of food

lost in type 1 diabetes

Question 2

what mechanisms maintain caloric homeostasis in the fed state?

Answer 2

glycogenesis
glycolysis
lipogenesis

Question 3

what mechanism maintain caloric homeostasis in the fasted state?

Answer 3

glycogenolysis
gluconeogenesis
lipolysis
fatty acid oxidation
ketogenesis

Question 4

what are the 4 primary mechanisms for switching between fed and starved states?

Answer 4

substrate supply
allosteric effectors
covalent modification
induction repression of enzymes

Question 5

what substrate is necessary for glycogenesis and lipogensis?

Answer 5

dietary glucose

Question 6

what substrate is required for ketone body synthesis by the liver?

Answer 6

high serum fatty acid concentration

Question 7

what substrates must be available for protein synthesis?

Answer 7

all 20 AAs

Question 8

when can the brain use ketone bodies?

Answer 8

when blood concentration is high

about 48 hours starved

Question 9

what are the 3 primary substrates involved in allosterically affecting the fed state?

Answer 9

glucose
fructose 2,6-P2
Malonyl-CoA

Question 10

what enzymes does glucose allosterically affect?

Answer 10

inhibits glycogen phosphorylase
stimulates glycogen synthase
stimulates glucokinase

Question 11

what enzymes does fructose 2,6-P2 allosterically affect?

Answer 11

inhibits fructose 1,6 bisphosphatase

stimulates phosphofructo-1-kinase (PFK1)

Question 12

what enzyme does malonyl-CoA allosterically affect?

Answer 12

inhibits carnitine palmitoyl coA transferase 1 (CPT1)

Question 13

what is CPT1?

Answer 13

rate limiting enzyme in oxidation of fatty acids

inhibited in fed state bc don’t want fats you just made to be broken down immediately

Question 14

what substrate is required to transport long chain fatty acids into the mitochondrial matrix space?

Answer 14

carnitine

Question 15

where does fatty acid oxidation occur?

Answer 15

mitochondrial matrix space

Question 16

what are the 2 primary substrates involved in allosterically regulating the fasted state?

Answer 16

long chain acyl coA

acetyl coA

Question 17

what enzyme does long chain acyl CoA allosterically affect?

Answer 17

inhibits acetyl CoA carboxylase to prevent fat production

Question 18

what enzymes does acetyl CoA allosterically affect?

Answer 18

inhibits pyruvate dehydrogenase (makes pyruvate)

stimulates pyruvate carboxylase (makes oxaloacetate and eventually glucose)

Question 19

what is the primary covalent modification that affects switching between fed and starved states?

Answer 19

phosphorylation
nonphosphorylated = fed
phosphorylated = starved

Question 20

high insulin
low glucagon
low cAMP
low PKA activity

Answer 20

fed state

Question 21

low insulin
high glucagon
high cAMP
high PKA

Answer 21

starved state

Question 22

what are the rate limiting enzymes impacted by induction-repression pathways in the fed state?

Answer 22

glucokinase- glycolysis
G6P dehydrogenase -pentose phosphate
acetyl-CoA carboxylase- fatty acid synthesis

Question 23

in the well fed state, what enzyme accounts for 10% of total liver enzymes?

Answer 23

fatty acid synthase

Question 24

what transcription factors does insulin act on?

Answer 24

inhibits forkhead transcription factor

stimulates SREBP-1

Question 25

what transcription factor does glucagon act on?

Answer 25

CREB

Question 26

what are the 2 rate limiting enzymes impacted by induction-repression pathways in the fed state?

Answer 26

glucose 6 phosphatase
PEP carboxykinase (only subject to regulation by transcription)

Question 27

what is hexokinase 4?

Answer 27

glucokinase

glucose sensor in the liver

Question 28

what makes glucokinase different from the other hexokinases?

Answer 28

higher Km

allows glucokinase to sense and respond immediately to the glucose concentration in the blood

Question 29

what is fructose 2,6-bisphosphate?

Answer 29

master regulator of glycolysis and gluconeogenesis in the liver
promotes glycolysis
inhibits gluconeogenesis

Question 30

how is fructose 2,6-bisphosphate made?

Answer 30

made from fructose 6-phosphate by a kinase
converted back to fructose 6-phosphate by a phosphatase
kinase and phosphatase located on same bifunctional enzyme

Question 31

how is the F2,6P2 bifunctional enzyme regulated?

Answer 31

phosphorylation
phosphorylated = active phosphatase
nonphosphorylated = active kinase

Question 32

can you synthesize glucose from fatty acids with even numbers of carbon atoms?

Answer 32

no

Question 33

why cant you synthesize glucose from fatty acids with even numbers of carbons?

Answer 33

1. no pathway exists for conversion of acetyl-CoA to glucose

2. the acetyl group of acetyl-CoA is completely oxidized to CO2 and water by the citric acid cycle

Question 34

can we synthesize glucose from fat?

Answer 34

fat= triacylglycerol
one glycerol and 3 fatty acids
glycerol can be converted to glucose, fatty acids cannot

Question 35

what is anaplerosis?

Answer 35

enzyme catalyzed reaction that results in net synthesis of a citric acid cycle intermediate

Question 36

which compound is recycled into the citric acid cycle to allow for continuous operation?

Answer 36

oxaloacetate

Question 37

what are 2 examples of anaplerotic pathways?

Answer 37

pyruvate + ATP +Co2 yields OAA + ADP +P

glutamate +NAD+ yields alpha-ketoglutarate + NADH + NH4+

Question 38

what are compounds called that are metabolized via an anaplerotic pathway?

Answer 38

glucogenic

Question 39

what are compounds called that are metabolized via acetyl-CoA?

Answer 39

ketogenic