Mark's Biochem 31: Gluconeogenesis And Maintenance Of Blood Glucose Levels

Front 1

major precursors of glucose in humans

Back 1

lactate, glycerol, and aas (alanine)

Front 2

sequences of gluconeogenesis that don't use enzymes from glycolysis

Back 2

1) pyruvate to phosphoenolpyruvate 2) fructose 1,6-biphosphate to fructose 6-phosphate 3) glucose 6-phosphate to glucose

Front 3

what combines with fatty acids to form triacylglycerols

Back 3

glycerol 3-phosphate - produced from glycolytic intermediates; secreted into blood as VLDLs

Front 4

respiration of diabteic ketoacidosis patients

Back 4

deep, relatively rapid Kussmaul respirations

Front 5

hypoglycemic coma symptoms

Back 5

flushed, wet skin

Front 6

diabetic ketoacidosis symptoms

Back 6

dehydraion, dry mucous membranes, loss skin turgor, low BP, rapid heartbeat, Kussmaul respirations

Front 7

what can glycorylated hemoglobin say about hyperglycemia levels

Back 7

helps determine extent of hyperglycemia over past 4-8 weeks

Front 8

when does glucose begin appearing in the urine

Back 8

blood glucose levels > 180 mg/dL

Front 9

actions of glucocorticoids causing muscle weakness

Back 9

stimulate degradation of muscle protein (increase gluconeogenesis)

Front 10

glucose formation from fatty acids (say 19 carbons long)

Back 10

3 carbons at w-end of odd chain fatty acid that form proprionyl CoA converted to glucose; remaining carbons form acetyl CoA

Front 11

where is lactate produced

Back 11

anaerobic glycolysis - exercising muscles, RBCs, adipocytes during fed state

Front 12

carbons of ethanol and glucose formation

Back 12

can't be used for gluconeogenesis - make acetyl CoA

Front 13

what is pyruvate produced in the liver from

Back 13

lactate and alanine

Front 14

how are the carbons of glycerol gluconeogenic

Back 14

form dihydroxyacetone phosphate (DHAP) which is a glycolytic intermediate

Front 15

what intermediate of the TCA cycle can be formed from propionyl CoA

Back 15

succinyl CoA

Front 16

What convertes PEP to pyruvate in glycolysis

Back 16

pyruvate kinase

Front 17

what is required to reverse PEP to pyruvate in gluconeogenesis

Back 17

a series of steps

Front 18

pyruvate to PEP step 1

Back 18

pyruvate is carboxylated by pyruvate carboxylase to form oxaloacetate (required biotin)

Front 19

pyruvate to PEP step 2

Back 19

CO2 added to pyruvate to form oxaloacetate is released in rxn catalyzed by phosphoenolpyruvate carboxykinase (PEPCK) to generate PEP

Front 20

where is pyruvate carboxylase found

Back 20

in mitochondira

Front 21

where is PEPCK

Back 21

cytosol and mitochondria

Front 22

oxaloacetate moveability

Back 22

doesn't readily cross mitochondrial membrane - can be converted to PEP by PEPCK in mitochondira or converted to malate or aspartate which can cross into the cytosol

Front 23

what does conversion of oxaloacetate to malate require

Back 23

NADH

Front 24

for every 2 molecules of glyceraldehyde 3-phosphate formed, one is converted into

Back 24

dihydroxyacetone phosphate (DHAP)

Front 25

what do DHAP and glyceraldehyde 3-phosphate condense to form

Back 25

fructose 1, 6-biphosphate by a reversal of the aldolase rxn

Front 26

how does glycerol enter into gluconeogenesis

Back 26

forms DHAP

Front 27

fxn of enzyme fructose 1,6-biphosphate

Back 27

releases organic phosphate to form fructose 6-phosphate; NOT a reversal of PFK-1 rxn - no ATP formation

Front 28

phosphoglucoisomerase fxn in gluconeogenesis

Back 28

convert fructose 6-phosphate into glucose 6-phosphate; reverse of its fxn in glycolysis

Front 29

glucose 6-phosphatase fxn

Back 29

hydrolyzes Pi and releases free glucose; ATP not generated, thus not a reversal of glycolysis rxn

Front 30

where is glucose 6-phosphatase located and what are its other fxns

Back 30

membrane of ER; gluconeogenesis and glucose production from breakdown of liver glycogen

Front 31

elevated NADH levels due to alcohol cause what

Back 31

inhibit conversion of malate to oxaloacetate in cytosol - leads to hypoglycemia due to inpaired gluconeogenesis

Front 32

what 3 sequences in the pathway of gluconeogenesis are regulated

Back 32

pyruvate to phosphoenolpyruvate; fructose 1,6-biphosphate to fructose 6-phosphate; glucose 6-phosphate to glucose

Front 33

steroid effects of glucose levels

Back 33

stimulate gluconeogenesis in part due to inducing synthesis of PEPCK

Front 34

what occurs due to pyruvate dehydrogenase inactivation under fasting condition

Back 34

pyruvate is not converted to acetyl CoA

Front 35

what occurs when pyruvate carboxylase is active

Back 35

acetyl CoA activates; pyruvate is converted to oxaloacetate

Front 36

major inducer of PEPCK

Back 36

cAMP

Front 37

what induces PEPCK promoter

Back 37

glucagon and epinephrine; cortisol activates at a different site

Front 38

what does inactivation of pyruvate kinase prevent

Back 38

cycling of PEP into pyruvate with net loss of energy; promotes net synthesis of glucose

Front 39

undre fasting conditions, where does the energy for gluconeogenesis come from

Back 39

B-oxidation of fatty acids

Front 40

what is glucose 6-phosphatase used in and why

Back 40

glycogenolysis and gluconeogenesis to produce free glucose from glucose 6-P

Front 41

hat do blood glucose levels drop to after 5-6 weeks of starvation

Back 41

only 65 mg/dL

Front 42

glucagon levels after a meal

Back 42

increase after high protein meal, decrease after high carb meal; relatively constant after a mixed meal

Front 43

what is the danger when excess insulin is injected in diabetic patients

Back 43

insulin inhibits lipolysis and ketone-body synthesis, so alternative fuels are not available to spare glucose

Front 44

major change that occurs in starvation

Back 44

dramatic elevation of blood ketone bodies after 3-5 days of fasting

Front 45

permanent neurologic deficits and even death may result if severe hypoglycemia is not corrected within

Back 45

6 to 10 hours

Front 46

how is glyceral derived from glucose

Back 46

dihydroxyacetone phosphate intermediate of glycolysis