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MCB 3010 > EXAM 3: Glycolysis I > Flashcards

EXAM 3: Glycolysis I Flashcards

1
Q

four major pathways of glucose utilization

A

storage

glycolysis

pentose phosphate pathway

synthesis of structural polysaccharides

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2
Q

four major pathways of glucose utilization:

storage

A

if the cell has enough energy, plenty of glucose is stored

can be stored in the polymeric form (starch, glycogen)

when [glucose] and [ATP] is high, glucose is stored

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3
Q

four major pathways of glucose utilization:

glycolysis

A

start of breaking down glucose for energy

generates energy via oxidation of glucose to ATP

short-term energy needs

can link to other pathways to generate more energy; end product is pyruvate

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4
Q

four major pathways of glucose utilization:

pentose phosphate pathway

A

generates NADPH via oxidation of glucose

for detoxification and the biosynthesis of lipids and nucleotides

product is critical for making nucleotides

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5
Q

four major pathways of glucose utilization:

synthesis of structural polysaccharides

A

cellulose, chitin in cell walls of bacteria, fungi, plants

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6
Q

importance of glycolysis

A

sequence of enzyme-catalyzed reactions by which glucose is converted into pyruvate (3C)

some of the free energy from oxidation is captured by synthesis of ATP and NADH

(NADH can help produce ATP through oxidative phosphorylation if oxygen is available)

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7
Q

summary of glycolysis

A

used: 1 glucose, 2ATP, 4ADP, 2Pi, 2NAD+
made: 2 pyruvate, 4ATP, 2NADH

NET:
1 glucose + 2ADP +2 Pi + 2NAD+
=
2 pyruvate + 2NADH + 2H+ +2ATP

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8
Q

why is glycolysis heavily regulated?

A

ensures proper use of nutrients

ensures production of ATP only when needed

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9
Q

dG for glycolysis

A

-146 kJ/mol for breakdown of glucose and 61 KJ/mol for synthesis of 2 ATP

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10
Q

getting monosaccharides for glycolysis

A

glucose can be transported into the cell via glucose transporter

glucose molecules can be cleaved from glycogen or starch (to get glucose-1P; must be converted to glucose-6P for glycolysis)

disaccharides can be hydrolyzed into monosaccharides

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11
Q

maltose

A

two glucose

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12
Q

lactose

A

glucose, galactose

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13
Q

sucrose

A

glucose, fructose

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14
Q

fructose, galactose, mannose

A

enter glycolysis at different paths

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15
Q

glycolysis overview

A

goal: extract energy without oxygen

first: activate glucose by phosphorylation
second: collect energy from high energy metabolites

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16
Q

3 irreversible reactions in glycolysis

A

very negative dG’*

point of regulation so glycolysis only goes forward when necessary – allosteric and reversible covalent regulation

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17
Q

GLYCOLYSIS: Step 1

A

phosphorylation of glucose

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18
Q

GLYCOLYSIS: Step 1, phosphorylation of glucose

A

traps glucose inside the cell

lowers intracellular [glucose] to allow further transport by glucose transporter

uses ATP

hexokinase

thermodynamically favorable, irreversible

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19
Q

GLYCOLYSIS: Step 1 phosphorylation of glucose

HEXOKINASE

A

glucose to glucose 6-phosphate

nucleophilic oxygen at C6 of glucose attacks last (gamma) phosphate of ATP

irreversible

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20
Q

GLYCOLYSIS: Step 2

A

phosphohexase isomeriaztion

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21
Q

GLYCOLYSIS: Step 2 phosphohexase isomerization

A

C1 of fructose is easier to phosphorylate in next step

allows for symmetrical cleavage of aldolase

unfavorable, reversible

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22
Q

GLYCOLYSIS: Step 2

phosphohexokinase isomerase

A

glucose 6-P to fructose 6-P

changing product concentrations allows reverse reaction

product concentration kept low to drive forward

unfavorable, reversible

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23
Q

GLYCOLYSIS: Step 3

A

2nd priming reaction

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24
Q

GLYCOLYSIS: Step 3 2nd priming reaction

A

Further activation of fructose

phosphofructokinase-1

first committed step of glycolysis

uses ATP

favorable, irreversible

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25
Q

GLYCOLYSIS: Step 3 2nd priming reaction

PHOSPHOFRUCTOKINASE-1

A

Fructose 6-P to fructose 1,6-bisphosphate

irreversible, favorable

first committed step of glycolysis

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26
Q

how is phosphofructokinase-1 tightly regulated?

A

tightly regulated by ATP, fructose-1,6-bisphosphate and other metabolites

prevents burning of glucose when there is plenty of ATP

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27
Q

why is the 2nd priming reaction with phosphofructokinase-1 the first committed step of glycolysis?

A

fructose 1,6-bisphosphate must continue through glycolysis where as prior products may be utilized in other pathways

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28
Q

GLYCOLYSIS: Step 4

A

aldol cleavage of fructose-1,6-bisphosphate

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29
Q

GLYCOLYSIS: Step 4 aldol cleavage

A

cleavage of 6 carbon sugar into two three carbon sugars

aldolase cleaves C-C bond between C3 and C4 in fructose-1,6-bisphosphate

makes glyceraldehyde-3P (ald) and dihydroxyacetone-phosphate (ket)

unfavorable, reversible

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30
Q

GLYCOLYSIS: Step 4 aldol cleavage

ALDOLASE

A

fructose-1,6-bisphosphate to glyceraldehyde-3P and dihydroxyaceone-phosphate

unfavorable, reversible

G3P concentration kept low to drive reaction
DHAP converted to G3P in a separate reaction so product concentration is kept low

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31
Q

GLYCOLYSIS: Step 5

A

triose phosphate interconverstion

32
Q

GLYCOLYSIS: Step 5 triose phosphate interconversion

A

allows glycolysis to proceed by one pathway

dihydroxyacetone phosphate to glyceraldehyde 3-phosphate via triose phosphate isomersase

unfavorable, reversible

END OF PREPARATORY PHASE

33
Q

GLYCOLYSIS: Step 5 triose phosphate interconversion

TRIOSE PHOSPHATE ISOMERASE

A

dihydroxyacetone phosphate to glyceraldehyde-3P

unfavorable
reversible

34
Q

Glycolysis: preparatory phase

A

phosphorylation of glucose and its conversion to glyceraldehyde-3-phosphate

first priming reaction (hexokinase, phosphohexase isomerase)
second priming reaction (phosphofructokinase 1)
cleavage of 6 carbon sugar into 2 3 carbon sugars

isomerase

35
Q

Glycolysis: payoff phase

A

oxidative conversion of glyceraldehyde 3-P to pyruvate and the coupled formation of NADH and ATP

36
Q

Where are 2 ATPs used in glycolysis?

A

prep phase:

hexokinase to phosphorylation glucose

phosphofructokinase 1 to make fructose-1,6-bisphosphate

37
Q

where are 4 ATPs made in glycolysis?

A

payoff phase:

1 ATP per phosphoglycerate kinase (2 total)

1 ATP per pyruvate kinase (2 total)

38
Q

GLYCOLYSIS: Step 6

A

oxidation and phosphorylation of glyceraldehyde 3P

39
Q

GLYCOLYSIS: Step 6 oxidative phosphorylation of glyceraldehyde 3P

A

generates high energy phosphate compound via incorporation of inorganic phosphate (NOT ATP)

allows for production of ATP in next step

oxidation of aldehyde (into carboxyl) and reduction of NAD+ (to NADH)

phosphorylation makes a phosphorylated carboxyl group

unfavorable, reversible; coupled to next reaction to pull

glyceraldehyde 3phosphate dehydrogenase

40
Q

GLYCOLYSIS: Step 6 oxidative phosphorylation of glyceraldehyde 3P

GLYCERALDEHYDE -3P DEHYDROGENASE

A

glyceraldehyde -3P + Pi to 1,3 bisphosphoglycerate

41
Q

GLYCOLYSIS: Step 7

A

phosphoryll transfer to ATP

substrate-level phosphorylation to make 2 ATP

1,3-bisphosphoglycerate donates phosphate group from C1 to ADP

phosphoglycerate kianse

favorable, reversible

42
Q

GLYCOLYSIS: Step 7
phosphoryl transfer to ATP

PHOSPHOGLYCERATE KINASE

A

1,3-bisphosphoglycerate + ADP to 3-phosphoglycerate + ATP

2 times

43
Q

GLYCOLYSIS: Step 8

A

migration of phosphate

44
Q

GLYCOLYSIS: Step 8

migration of phosphate

A

phosphoglycerate mutase catalyzes change in position of phosphate functional group within the molecule

3-phosphoglycerate to 2-phosphoglycerate

unfavorable, reversible

45
Q

GLYCOLYSIS: Step 8
migration of phosphate

PHOSPHOGLYCERATE MUTASE

A

3-phosphoglycerate to 2-phosphoglycerate

  • enzyme is phosphorylated
  • donates phosphate to C2 before removing phosphate at C3
  • 2,3-bisphosphoglycerate intermediate
  • phosphate from substrate ends up bound to enzyme at the end of reaction

reactant concentration kept high by phosphoglycerate kinase to push phosphoglycerate mutase reaction

46
Q

GLYCOLYSIS: Step 9

A

dehydration of 2-phosphoglycerate to phosphoenolpyruvate

47
Q

GLYCOLYSIS: Step 9

dehydration of 2-phosphoglycerate to PEP

A

generates high energy compound

slightly unfavorable, reversible

product concentration kept low

enolase

48
Q

GLYCOLYSIS: Step 9

ENOLASE

A

2-phosphoglycerate to phosphoenolpyruvate

49
Q

GLYCOLYSIS: Step 10

A

2nd production of ATP

50
Q

GLYCOLYSIS: Step 10

2nd production of ATP

A

substrate-level phosphorylation to make ATP

loss of phosphate from phosphoenolpyruvate yields an enol, tautomerizes into a ketone

favorable, irreversible

pyruvate kinase

51
Q

GLYCOLYSIS: Step 10

PYRUVATE KINASE

A

PEP + ADP to pyruvate and ATP

2 total

regulated by ATP, divalent metals, other metabolites

52
Q

tautomerization in step 10

A

changes molecule with high free energy to molecule with low free energy (favorable)

effectively lowers concentration of reaction product

drives reaction towards ATP formation

responsible for half of dG*’ = -61.9 kJ/mol

53
Q

fates of pyruvate: hypoxic or anaerobic conditions

A

2 ethanol + 2CO2

fermentation to ethanol in yeast

54
Q

fates of pyruvate: aerobic conditions

A 
2 acetyl-CoA + 2CO2
|
citric acid cycle
|
4CO2 + 4H2O

animal, plant, microbial cells under aerobic conditions; all carbons oxidized, many NADH, FADH2

55
Q

fates of pyruvate: hypoxic or anaerobic conditions

A

2 lactate

fermentation to lactate in contracting muscle, erythrocytes, microorganisms

56
Q

glycogen phosphorylase

A

first enzyme

breaks a1-4 linkages between glucose molecules via phosphorolysis

cleaves until 4 glucoses remain before a branch point

product: glucose-1P

57
Q

phosphorolysis

A

uses inorganic phosphate instead of water in hydrolysis to break bond

58
Q

glycogen debranching enzyme

A

second enzyme

transferase activity
glucosidase activity

59
Q

glycogen debranching enzyme

transferase activity

A

transfers 3 of 4 remaining glucoses of one branch to another branch

60
Q

glycogen debranching enzyme

glucosidase activity

A

cleaves off remaining glucose that is attached a1-6 as glucose via hydrolysis

61
Q

phosphoglucomutase

A

third enzyme

converted glucose-1P into glucose6P which can feed into glycolysis

62
Q

glucose-6-phosphatase

A

in liver

cleaves off phosphate so glucose can be transported in to the blood for other organs

63
Q

maltase

A

cleaves maltose

hydrolysis

64
Q

lactase

A

cleaves lactose

hydrolysis

65
Q

sucrase

A

cleaves sucrose

hydrolysis

66
Q

fructose route 1

A

hexokinase + ATP

can make fructose 6 phosphate

second reaction to make fructose 1,6-bisphosphate to go into glycolysis

67
Q

fructose route 2

A

fructokinase + ATP: makes fructose 1 phosphate

fructose 1 phosphate aldolase: cleaves fructose-1-phosphate to make dihydroxyacetone phosphate and glyceraldehyde

trios kinase + ATP phosphorylates glyceraldehyde so it can enter glycolysis

68
Q

galactokinase

A

synthesizes galactose-1P from galactose using ATP

69
Q

UDP-glucose galactose-1-phosphate uridylyltransferase

A

trades groups

UDP from UDP-glucose to C1 on galactose

Phosphate from galactose-1P to C1 on glucose

glucose 1P becomes glucose 6P via phosphoglucomutase

70
Q

UDP glucose 4 epimerase

A

switches OH on chiral carbon 4 of galactose portion of UDP-galactose to make UDP-glucose

71
Q

anaerobic glycolysis: fermentation

A

generation of ATP without consuming oxygen

final reaction reduces pyruvate to another product to produce NAD+

process is used in production of food

72
Q

lactic acid fermentation

A

animals, some bacteria

reversible reduction of pyruvate to lactate

glycogen in muscle becomes glucose becomes lactate. lactate transports to liver to be converted to glucose using ATP
glucose sent back to muscle to restore glycogen stores

erythrocytes do lactic acid fermentation bc no mitochondria

73
Q

cori cycle

A

cycle with lactate and liver

74
Q

lactate dehydrogenase

A

reduces pyruvate to lactate and oxidizes NADH to NAD+

75
Q

ethanol fermentation

A

yeast

pyruvate to acetaldehyde = irreversible

pyruvate decarboxylase

alcohol dehydrogenase

CO2 produces in first step = carbonation, dough rising

76
Q

pyruvate decarboxylase

A

pyruvate to acetaldehyde

humans don’t have this

77
Q

alcohol dehydrogenase

A

acetaldehyde to ethanol

humans have this for ethanol metabolism (reverse of fermentation)

MCB 3010 (12 decks)

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