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My Kaplan Biochemistry Ch 8-12 > Ch. 9: Carbohydrate Metabolism I > Flashcards

Ch. 9: Carbohydrate Metabolism I Flashcards

1
Q

what drives glucose entry into the cells

A

concentration

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2
Q

where is GLUT 2 located

A

hepatocytes and pancreatic cells

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3
Q

what does GLUT 2 do

A

captures excess glucose from the digestive tract primarily for storage

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4
Q

when does GLUT 2 function

A

when blood glucose levels are high until the concentration drops below the Km T (which is high) for the transporter

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5
Q

where is GLUT 4 located

A

adipose tissue and muscle

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6
Q

how does GLUT 4 function with insulin

A

when insulin is high, transporters move from inside cell to membrane

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7
Q

how high is the Km of GLUT 4 in relationship to nl blood glucose levels

A

Km is slightly higher than normal blood glucose

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8
Q

what does GLUT 4 do

A

captures excess blood glucose for for storage in muscles (as glycogen) and adipose tissue (DHAP)

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9
Q

what occurs (big picture) during glycolysis

A
  • glucose is converted into two pyruvate molecules
  • which release energy that
  • is captured in two substrate level phosphorylations and
  • one oxidation reaction
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10
Q

how are the products of glycolysis used by the body (big picture)

A

if oxygen + mitochondria, NADH feeds into aerobic respiratory pathway

if no oxygen or mitochondria, anaerobic energy

sometimes, intermediates for other pathways

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11
Q

what do hexokinase and glucokinase do

A

phosphorylate glucose inside the cell to prevent it from leaving the cell via the transporter

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12
Q

where is hexokinase located

A

most tissues (GLUT 4)

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13
Q

where is glucokinase located

A

hepatocytes and pancreas cells (GLUT 2)

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14
Q

what does phosphofructokinase-1 do

A

rate-limiting enzyme and main control point in glycolysis

phosphorylates fructose

activated (turns on glycolysis) by AMP and citrate and inhibited (turns off glycolysis) by ATP

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15
Q

what does phosphofructokinase-2 do

A

phosphorylates F6P to F26P, which activated PFK-1

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16
Q

what does glyceraldehyde-3-phosphate dehydrogenase do

A

catalyzes an oxidation and addition of inorganic phosphate to its substrate –> high energy intermediate: 1,3 - biphosphoglycerate

reduces NAD+ to NADH

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17
Q

what does 3-phosphoglycerate kinase do

A

transfers the high-energy phosphate from 1,3 - biphosphoglycerate to ADP –> ATP

substrate-level phosphorylation

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18
Q

what occurs during substrate-level phosphorylation

A

ADP is directly phosphorylated to ATP using high energy intermediate

not oxygen dependent, like oxidative phosphorylation

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19
Q

what does pyruvate kinase do

A

catalyzes substrate-level phosphorylation of ADP –> ATP and pyruvate

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20
Q

what occurs during fermentation

A

anaerobic ATP production

lactate dehydrogenase reduces pyruvate to lactate and oxidizes NADH to NAD+

21
Q

what is dihydroxyacetone phosphate (DHAP)

A

intermediate of glycolysis

used in hepatic and adipose tissue for tracylglycerol synthesis

22
Q

what are the irreversible enzymes of glycolysis

A

hexokinase, glucokinase, PFK-1, pyruvate kinase

23
Q

how is ATP produced in erythrocytes

A

anaerobic glycolysis

24
Q

what is the disaccharide precursor to galactose

A

lactose (glucose + galactose)

25
Q

what is the disaccharide precursor to fructose

A

sucrose

26
Q

what enzyme phosphorylates fructose

A

fructokinase

27
Q

what enzyme phosphorylates galactose

A

galactokinase

28
Q

what can pyruvate be converted to in the mitochondria

A

acetyl coA –>citric acid cycle (makes ATP)

OR –> fatty acid synthesis (when enough ATP)

29
Q

what enzyme converts pyruvate to acetyl coA

A

pyruvate dehydrogenase enzyme (PDH)

30
Q

what is glycogen

A

a branched polymer of glucose, glucose in its storage form

31
Q

where is glycogen stored

A

the cytoplasm as a granule

32
Q

where is glycogen synthesized

A

the liver and skeletal muscle

33
Q

what occurs during glycogenesis (big picture)

A

glycogen granules are synthesized

34
Q

what is glycogenin

A

the core protein of a glycogen granule

35
Q

what is glycogen synthase

A
  • rate-limiting enzyme of glycogenesis
  • forms alpha 1,4 glycosidic bond
  • stimulated by insulin, inhibited by epinephrine
36
Q

what does branching enzyme do

A

introduces alpha 1,6 linkages to glycogen, creating branches

1,4 goes 4ward…1,6 puts a branch in the mix

37
Q

what occurs during glycogenolysis (big picture)

A

glycogen is broken down

38
Q

what is the rate limiting enzyme of glycogenolysis

A

glycogen phosphorylase –> breaks alpha 1,4 bonds, stops when reaching branches

39
Q

what does debranching enzyme do

A

deconstructs branches in glycogen by

  • breaking adjacent 1,4 bonds,
  • moving the oligoglucose chain to the exposed end of the other chain,
  • hydrolyzing the 1,6 bond
40
Q

glycogen storage diseases

A

genetic deficiencies that result in the accumulation/lack of glycogen in the tissues

41
Q

what occurs during glyconeogenesis (big picture)

A

the liver produces glucose during times of fasting to maintain blood glucose levels by essentially reversing glycolysis

42
Q

what can glycogenic amino acids (except leucine and lysine) be converted into

A

intermediates that feed into gluconeogenesis

43
Q

what can ketogenic amino acids be converted into

A

ketone bodies which are used for alternative fuels during prolonged starvation

44
Q

what does pyruvate carboxylase do

A

mitochondrial enzyme

activated by acetyl co-A (from fatty acids) to produce oxaloacetate

45
Q

what does phosphoenolpyruvate carboxykinase (PEPCK)

A

converts OAA to PEP in the cytoplasm with GTP

46
Q

what does fructose 1,6 bisphosphatase do

A

key control enzyme of gluconeogenesis

reverses action of PFK-1, removing phosphate from biphosphorylated fructose, in the cytoplasm

47
Q

what does glucose-6-phosphatase do

A

circumvents gucokinase and hexokinase, allowing free glucose to be transported out of the cell

48
Q

what are the major functions of the pentose phosphate pathway/hexose monophosphate shunt

A
  • produce NADPH

- source of ribose phosphate for nucleotide synthesis

49
Q

what is the rate limiting enzyme of PPP

A

glucose-6-phosphate dehydrogenase (G6PD)

produces NADPH

My Kaplan Biochemistry Ch 8-12 (5 decks)

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