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BIOL 2421 - Cellular Biochem > 15. glycolysis > Flashcards

15. glycolysis Flashcards

1
Q

define metabolism

A

the highly organized/regulated collection of chemical transformations carried out by living cells. Carried out by metabolic pathways

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2
Q

what are metabolic pathways

A

a series of sequential reactions. The product of one becomes the substrate for the next

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3
Q

what are metabolites

A

small molecules that are intermediates in the degradation or biosynthesis reactions of biopolymers

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4
Q

what is intermediary metabolism

A

the study of metabolites throughout metabolic pathways

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5
Q

T or F; metabolic pathways can be highly connected and share intermediates

A

true

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6
Q

what is anabolism

A

synthesis of small molecules into large molecules

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7
Q

what is catabolism

A

breakdown of large molecules into smaller molecules

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8
Q

which type of metabolism requires an input of energy

A

anabolic pathways

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9
Q

what type of energy does anabolism require an input of

A

ATP (phosphoryl group transfer) and NADH/NADPH/FADH2 (reduced electron carriers)

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10
Q

which type of metabolism releases energy

A

catabolic pathways

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11
Q

describe the release of energy in catabolism

A

regenerates ATP from ADP and Pi, and regenerates the reduced electron carriers from their oxidized forms (NAD+, NADP+, FAD)

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12
Q

what are amphibolic pathways

A

pathways that are either catabolic or anabolic depending on the energy conditions of the cell

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13
Q

T or F: most metabolic reactions in cells are at steady state

A

true

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14
Q

define steady state

A

the amount of each intermediate is not changing

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15
Q

define flux

A

the rate of flow through the pathway

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16
Q

T or F: most cells have the enzymes to carry out both the degradation and synthesis of important biomolecules

A

true

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17
Q

T or F: feedback can activate or inhibit a metabolic pathway

A

true

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18
Q

explain how glucose plays a central role in the metabolism of animals and plants

A
  • rich in potential energy (G’o = -2840kj/mol)
  • large amounts can be stored
  • quick release from storage when needed
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19
Q

where does glycolysis occur

A

in the cytosol

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20
Q

how many steps is glycolysis

A

10

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21
Q

what is the first 5 steps of glycolysis called

A

the preparatory phase

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22
Q

what does the preparatory phase produce

A

glyceraldehyde-3-phosphate

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23
Q

what is the cost of the preparatory phase

A

2 ATP

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24
Q

what is the last 5 steps of glycolysis called

A

the payoff phase

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25
Q

what does the payoff phase produce

A

pyruvate

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26
Q

what is the benefit of the payoff phase (ie what’s the payoff)

A

4 ATP

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27
Q

what happens to pyruvate after glycolysis

A
  • complete oxidation to CO2 to produce reduced electron carriers for the ETC
  • lactic acid fermentation to regenerate NAD+
  • ethanol fermentation
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28
Q

step 1: what is the reagent and product

A

glucose –> glucose-6-phosphate

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29
Q

step 1: how does it happen

A

phosphorylation at C6 turns glucose into G6P

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30
Q

step 1: what phosphorylates glucose

A

ATP is the phosphoryl donor

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31
Q

step 1: is it reverisble

A

no

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32
Q

step 1: what is the purpose of phosphorylation

A

it “primes” glucose for subsequent reactions

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33
Q

step 1: what effect does phosphorylation have on glucose (hint: think location)

A

phosphorylation traps glucose in the cell

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34
Q

step 1: what enzyme is used for glucose phosphorylation from ATP

A

hexokinase

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35
Q

step 1: describe the G’o

A

relatively large G’o (because energy in this step was raised)

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36
Q

step 1: does hexokinase need a substrate

A

yes

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37
Q

step 1: what substrate does hexokinase (and all the other kinases) need

A

(MgATP)^2-

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38
Q

step 1: since MgATP2- is the substrate for hexokinase, what does that make Mg2+. What is the purpose of Mg2+

A

it’s an essential cofactor. It shields negative charges in the active site

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39
Q

step 2: what enzyme is used

A

phosphohexose isomerase (requires Mg2+)

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40
Q

step 2: what is the reagent and product

A

glucose-6-phosphate –> fructose-6-phosphate

aldose to ketose

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41
Q

step 2: is it reversible

A

yes

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42
Q

step 2: what is the purpose of aldose to ketose

A

C1 is now able to be phosphorylated just like C6 was

because the goal is to have glucose as a mirror image

43
Q

step 2: what is required to convert the aldose to the ketose

A

we need to open the ring in the active site to temporarily revert glucose to linear form, then we can form the ketose

44
Q

step 3: what is the reagent and product

A

fructose-6-phosphate –> fructose 1,6-bisphosphate

45
Q

step 3: what happens to make the product

A

F6P is phosphorylated to make the product

46
Q

step 3: where does the phosphate come from to phosphorylate F6P

A

ATP

47
Q

step 3: what enzyme uses the P from ATP to phosphorylate F6P

A

phosphofructokinase-1

48
Q

step 3: is it reversible

A

no! phosphofructokinase-1 commits these carbons to glycolysis

49
Q

step 3: what does phosphofructokinase-1 need for proper kinase activity

A

Mg2+

50
Q

step 4: what is the reagent and product

A

fructose 1,6-bisphosphate –> glyceraldehyde 3-phosphate AND dihydroxyacetone phosphate

51
Q

step 4: what is glyceraldehyde 3-phosphate

A

aldose, phosphorylated version of glyceraldehyde

52
Q

step 4: what is dihydroxyacetone phosphate

A

ketose, phosphorylated version of dihydroxyacetone

53
Q

step 4: what happens to fructose 1,6-bisphosphate in this step

A

it is cleaved into the two products, which requires the ring opening

54
Q

step 4: when the ring is opened to make the two products, is there a tetrahedral intermediate

A

yes

55
Q

step 4: what enzyme is used

A

aldolase

56
Q

step 5: what is the reagent and product

A

dihydroxyacetone phosphate –> glyceraldehyde 3-phosphate

57
Q

step 5: how does DHAP become G3P

A

isomerization

58
Q

step 5: what are we left with + why

A

2 molecules of G3P, because one was made in this step and one was pre existing from the last step

59
Q

step 5: what enzyme is used

A

triose phosphate isomerase

60
Q

step 6: what is the reagent and product

A

glyceraldehyde 3-phosphate –> 1,3-bisphosphoglycerate

61
Q

step 6: how does the conversion of G3P to 1,3BPG occur

A

oxidation with the help of Pi and NAD+

62
Q

step 6: what enzyme is used

A

glyceraldehyde 3-phosphate dehydrogenase

63
Q

step 6: other than 1,3BPG, what is produced

A

2 NADH and 2 H+

64
Q

step 6: what is the role of the electron carrier NAD+

A

it’s a co-substrate of the dehydrogenase enzyme

65
Q

step 6: how are NADH and H+ formed

A

two electrons and a proton from the oxidation of G3P to 1,3BPG are transferred to the NAD+

66
Q

step 6: what happens to NAD+ levels after this step

A

NAD+ levels in the cell are very low, so NAD+ is eventually regenerated down the road

67
Q

step 6: endergonic or exergonic

A

endergonic (non-spontaneous)

68
Q

how do we make step 6 spontaneous (exergonic)

A

by coupling it with step 7

69
Q

step 7: what is the reagent and product

A

1,3-bisphosphoglycerate –> 3-phosphoglycerate

70
Q

step 7: how is 3-phosphoglycerate formed

A

hydrolysis of the high energy phosphoryl group from 1,3BPG

71
Q

step 7: where does the hydrolyzed phosphoryl group go (came from 1,3BPG)

A

it is transferred to ADP –> ATP

72
Q

step 7: what enzyme is used

A

phosphoglycerate kinase

73
Q

step 7: how many ATP are produced

A

2

74
Q

step 7: 1,3BPG was one of the molecules with a large negative G’o from bioenergetics. What does this mean for glycolysis

A

the products of this step (3-phosphorglycerate) are stabilized (due to ionization and resonance), and this step is super exergonic

75
Q

step 7: what is the term for the transfer of a phosphoryl group from a high energy compound (ie BPG) to ADP by a soluble enzyme in the cytosol

A

substrate level phosphorylation

76
Q

step 7: does the enzyme require Mg2+

A

yes

77
Q

what does coupling of steps 6 and 7 achieve

A

makes the endergonic step 6 into an exergonic step

78
Q

step 8: what is the reagent and product

A

3-phosphoglycerate –> 2-phosphoglycerate

79
Q

step 8: how is 2-phosphoglycerate made

A

the phosphoryl group on 3-phosphoglycerate is shifted to C2 from C3 to produce 2-phosphoglycerate

80
Q

step 8: what enzyme is used

A

phosphoglycerate mutase

81
Q

step 8: does phosphoglycerate mutase require Mg2+

A

yes

82
Q

step 9: what is the reagent and product

A

2-phosphoglycerate –> phosphoenolpyruvate

83
Q

step 9: how is phosphoenolpyruvate produced

A

water is removed from 2-phosphoglycerate to produce phosphoenolpyruvate

84
Q

step 9: what enzyme is used

A

enolase

85
Q

step 9: phosphoenolpyruvate was one of the molecules with a large negative G’o from bioenergetics. What does this mean for glycolysis

A

the hydrolysis product (pyruvate) is stabilized by isomerization

86
Q

step 10: what is the reagent and product

A

phosphoenolpyruvate –> pyruvate

87
Q

step 10: how is pyruvate produced

A

hydrolysis

88
Q

step 10: what enzyme is used

A

pyruvate kinase

89
Q

step 10: does pyruvate kinase require Mg2+

A

yes

90
Q

step 10: what else is produced

A

ATP

91
Q

step 10: how much ATP is produced

A

2

92
Q

step 10: how much of the standard free energy is retained in the ATP

A

half; the other half is released

93
Q

T or F: for all 10 steps, the gibbs free energy is either negative or zero

A

true

94
Q

describe the delta G value for the overall sum of the reactions

A

negative

95
Q

which of the 10 reactions has a large negative delta G value

A

1, 3, and 10

96
Q

for reactions 1, 3, and 10 (ones having large negative G), why are they considered regulatory points in metabolism

A

they’re both metabolically irreversible and regulated

97
Q

describe the feeder pathway for starch

A

broken down by a-amylases in salivary glands = short oligosaccharides. Pancreatic a-amylases continue = maltose. Maltose is degraded to glucose by intestinal enzymes

98
Q

describe the feeder pathway of dietary glycogen (animal products)

A

very similar to starch

99
Q

describe the feeder pathway of endogenous glycogen (glucose in our bodies)

A

broken down via phosphorylases in the liver/muscle. Glucose 1-phosphate is cleaved off, which isomerizes to glucose 6-phosphate
(this is phosphorolysis, not hydrolysis)

100
Q

describe the feeder pathway of sucrose

A

sucrose is cleaved by sucrases into glucose and fructose. Fructose can enter glycolysis via the muscle and kidney, or by the liver

101
Q

describe the feeder pathway for fructose in the muscle/kidney

A

fructose is phosphorylated by hexokinase and enters glycolysis

102
Q

describe the feeder pathway for fructose in the liver

A

fructose is phosphorylated by fructokinase at C1 (not C6). F 1-P is then cleaved into two products that enter glycolysis via G3P

103
Q

describe the feeder pathway for mannose

A

mannose is phosphorylated by hexokinase to mannose 6-phosphate. M6P is then isomerized to fructose 6-phosphate

BIOL 2421 - Cellular Biochem (21 decks)

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