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BIOC 4331 > Glycolysis > Flashcards

Glycolysis Flashcards

1
Q

Structure of D-glucose

A

D-Glucose

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2
Q

Structure and name of ATP

A

Adenosine Triphosphate

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3
Q

Glucose is what?

A

Reduced carbon (energy)

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4
Q

Two stages of glycolysis

A

I) Investment phase (glycolysis I-V) converts 1 D-glucose into 2 glyceraldehyde-3-phosphate, requires two adenosine triphosphate (-2 ATP)

II) Payoff phase (glycolysis (VI-X) converts 2 glyceraldehyde-3-phosphate into 2 pyruvate, generates four adenosine triphosphate (+4 ATP) and 2 reduced nicotinamide adenine dinucleotide (+2 NADH + H+) which must be oxidised later to regenerate NAD+ and continue glycolysis

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5
Q

Glycolysis I:

reactant

A

Glycolysis I:

reactant: D-Glucose

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6
Q

Glycolysis I:

product

A

Glycolysis I:

product: Glucose-6-phosphate

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7
Q

Glycolysis I:

type of reaction

A

Glycolysis I:

type of reaction: Phosphoryl transfer by kinase

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8
Q

Glycolysis I:

reactant

product

A

Glycolysis I:

reactant: D-Glucose

product : Glucose 6-phosphate

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9
Q

Glycolysis I:

enzyme

A

Glycolysis I:

enzyme: hexokinase (all cells), glucokinase (isoenzyme of hexokinase present only in liver)

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10
Q

Glycolysis I:

cofactor

A

Glycolysis I:

cofactor: Mg+, adenosine triphosphate (-1 ATP)

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11
Q

Glycolysis I:

reactant

product

type of reaction

enzyme

cofactor

A

Glycolysis I:

reactant: D-Glucose
product: Glucose 6-phosphate

type of reaction: Phosphoryl transfer by kinase

enzyme: hexokinase (all cells), glucokinase (isoenzyme of hexokinase present only in liver)
cofactor: Mg+,adenosine triphosphate (-1 ATP)

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12
Q

Purpose of glycolysis I

A

Phosphorylation traps glucose in the cell by making it unrecognisable to transport proteins such as Glucose transporter 1 (GLUT1), which removes it from equilibrium. G6P is charged and cannot diffuse through cell membrane. Because the reaction is driven by ATP, it is highly favourable (13.9 (Glucose -> G6P) - 30.5 (ATP -> ADP) = -16.6kJ/mol), causing the glucose level in the cell to remain low, causing the cell to absorb more glucose from the environment.

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13
Q

KM of hexokinase compared to average blood concentration of D-glucose

A

Hexokinase has a KM of .1mM, while the fasting blood concentration of glucose is 5mM, 50x higher than the amount required for Vmax/2. Hexokinase is saturated, phosphorylation of glucose is a rapid process.

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14
Q

What inhibits hexokinase activity?

A

Hexokinase is inhibited by the product of its reaction, glucose-6-phosphate. This is a very important regulatory step, since it prevents the consumption of too much cellular ATP to form G6P when glucose is not limiting.

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15
Q

G6P

A

Glucose 6-phosphate

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16
Q

Free energy of D-glucose to glucose-6-phosphate

A

+13.9 kJ/mol

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17
Q

What reaction is the phosphorylation of glucose coupled to?

A

ATP hydrolysis -30.5kJ/mol

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18
Q

KM of glucokinase compared to average blood concentration of D-glucose

A

Glucokinase has a KM of 10mM, which assures it will only work when glucose is high. Glucokinase is used to make glycogen and is induced by insulin.

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19
Q

Glucose enters the cell how

A

1) Diffusion, glucose is uncharged 2) Facilitated diffusion using a transport protein such as Glucose transporter 1 (GLUT1) 3) Active transport. Unlike two options above, this requires ATP.

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20
Q

Structure of G6P

A

Glucose 6-phosphate (G6P)

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21
Q

Glycolysis II:

reactant

A

Glycolysis II:

reactant: Glucose 6-phosphate (G6P)

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22
Q

Glycolysis II:

product

A

Glycolysis II:

product: Fructose-6-phosphate

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23
Q

Glycolysis II:

reactant

product

A

Glycolysis II:

reactant: Glucose-6-phosphate
product: Fructose-6-phosphate

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24
Q

Glycolysis II:

type of reaction

A

Glycolysis II:

type of reaction: isomerisation

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25
Q

Glycolysis II:

enzyme

A

Glycolysis II:

enzyme: Phosphoglucoisomerase

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26
Q

Glycolysis II:

reactant

product

type of reaction

enzyme

cofactor

A

Glycolysis II:

reactant: Glucose-6-phosphate
product: Fructose-6-phosphate

type of reaction: isomerisation

enzyme: Phosphoglucoisomerase
cofactor: none

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27
Q

Glycolysis III:

reactant

A

Glycolysis III:

reactant: Fructose-6-phosphate

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28
Q

Glycolysis III:

product

A

Glycolysis III:

product: Fructose-1,6-bisphosphate

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29
Q

Glycolysis III:

reactant

product

A

Glycolysis III:

reactant: Fructose-6-phosphate
product: Fructose-1,6-bisphosphate

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30
Q

Glycolysis III:

type of reaction

A

Glycolysis III:

type of reaction: phosphoryl transfer by kinase

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31
Q

Glycolysis III:

enzyme

A

Glycolysis III:

enzyme: Phosphofructokinase 1

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32
Q

Glycolysis III:

cofactor

A

Glycolysis III:

cofactor: Mg+, adenosine triphosphate (-1 ATP)

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33
Q

Glycolysis III:

reactant

product

type of reaction

enzyme

cofactor

A

Glycolysis III:

reactant: Fructose-6-phosphate
product: Fructose-1,6-bisphosphate

type of reaction: phosphoryl transfer by kinase

enzyme: Phosphofructokinase 1
cofactor: Mg+, adenosine triphosphate (-1 ATP)

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34
Q

diphosphate vs. bisphosphate

A

In a diphosphate, the 2 phosphate groups in the compound are directly attached to one another. In a bisphosphate, the 2 phosphate groups in the compound are attached to different atoms on the compound, meaning that they are not attached to one another.

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35
Q

Structure of fructose-6-phosphate

A

Fructose-6-phosphate

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36
Q

Structure of fructose-1,6-bisphosphate

A

Fructose-1,6-bisphosphate

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37
Q

Structure of D-fructose

A

D-Fructose

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38
Q

Glycolysis IV:

reactant

A

Glycolysis IV:

reactant: Fructose-1,6-bisphosphate

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39
Q

Glycolysis IV:

product

A

Glycolysis IV:

product: Glyceraldehyde-3-phosphate (G3P) (an aldose) AND Dihydroxyacetone phosphate (a ketose)

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40
Q

Glycolysis IV:

reactant

product

A

Glycolysis IV:

reactant: Fructose-1,6-bisphosphate
product: Glyceraldehyde-3-phosphate (G3P) (an aldose) AND Dihydroxyacetone phosphate (a ketose)

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41
Q

Glycolysis IV:

type of reaction

A

Glycolysis IV:

type of reaction: β aldol cleavage

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42
Q

Glycolysis IV:

enzyme

A

Glycolysis IV:

enzyme: Aldolase

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43
Q

Glycolysis IV:

reactant

product

type of reaction

enzyme

cofactor

A

Glycolysis IV:

reactant: Fructose-1,6-bisphosphate
product: Glyceraldehyde-3-phosphate (aldose) AND Dihydroxyacetone phosphate (ketose)

type of reaction: β aldol cleavage

enzyme: Aldolase cofactor: none

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44
Q

Structure of dihydroxyacetone

A

Dihydroxyacetone

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45
Q

Structure of glyceraldehyde

A

Glyceraldehyde

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46
Q

Structure of dihydroxyacetone phosphate

A

Dihydroxyacetone phosphate

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47
Q

Structure of glyceraldehyde-3-phosphate

A

Glyceraldehyde 3-phosphate (G3P)

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48
Q

Glycolysis V:

reactant

A

Glycolysis V: ALSO PROCEEDS IN REVERSE, G3P moves on to glycolysis II (> glycolysis V)

reactant: Dihydroxyacetone phosphate (a ketose)

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49
Q

Glycolysis V:

product

A

Glycolysis V: ALSO PROCEEDS IN REVERSE, G3P moves on to glycolysis II (> glycolysis V)

product: Glyceraldehyde-3-phosphate (G3P) (an aldose)

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50
Q

Glycolysis V:

reactant

product

A

Glycolysis V: ALSO PROCEEDS IN REVERSE, G3P moves on to glycolysis II

reactant: Dihydroxyacetone phosphate
product: Glyceraldehyde-3-phosphate (G3P)

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51
Q

Glycolysis V:

type of reaction

A

Glycolysis V: ALSO PROCEEDS IN REVERSE, G3P moves on to glycolysis II

type of reaction: Isomeraisation

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52
Q

Glycolysis V:

enzyme

A

Glycolysis V: ALSO PROCEEDS IN REVERSE, G3P moves on to glycolysis II

enzyme: Triose phosphate isomerase

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53
Q

Glycolysis V:

reactant

product

type of reaction

enzyme

cofactor

A

Glycolysis V: ALSO PROCEEDS IN REVERSE, G3P moves on to glycolysis II

reactant: Dihydroxyacetone phosphate
product: Glyceraldehyde-3-phosphate (G3P)

type of reaction: Isomeraisation

enzyme: Triose phosphate isomerase
cofactor: none

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54
Q

What step of glycolysis is this?

A

Glycolysis I

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55
Q

What step of glycolysis is this?

A

Glycolysis II

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56
Q

What step of glycolysis is this?

A

Glycolysis III

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57
Q

What step of glycolysis is this?

A

Glycolysis IV

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58
Q

What step of glycolysis is this?

A

Glycolysis V

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59
Q

GLUT1

A

Glucose transporter 1 (GLUT1), also known as solute carrier family 2, facilitated glucose transporter member 1 (SLC2A1), is a uniporter protein that in humans is encoded by the SLC2A1 gene. GLUT1 facilitates the transport of glucose across the plasma membranes of mammalian cells. Energy-yielding metabolism in erythrocytes (RBC) depends on a constant supply of glucose from the blood plasma, where the glucose concentration is maintained at about 5mM. Glucose enters the erythrocyte by facilitated diffusion via a specific glucose transporter, at a rate about 50,000 times greater than uncatalyzed transmembrane diffusion. The glucose transporter of erythrocytes (called GLUT1 to distinguish it from related glucose transporters in other tissues) is a type III integral protein with 12 hydrophobic segments, each of which is believed to form a membrane-spanning helix. The detailed structure of GLUT1 is not known yet, but one plausible model suggests that the side-by-side assembly of several helices produces a transmembrane channel lined with hydrophilic residues that can hydrogen-bond with glucose as it moves through the channel. GLUT1 is responsible for the low level of basal glucose uptake required to sustain respiration in all cells. Expression levels of GLUT1 in cell membranes are increased by reduced glucose levels and decreased by increased glucose levels. GLUT1 is also a major receptor for uptake of Vitamin C as well as glucose, especially in non vitamin C producing mammals as part of an adaptation to compensate by participating in a Vitamin C recycling process. In mammals that do produce Vitamin C, GLUT4 is often expressed instead of GLUT1.

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60
Q

Glycolysis II:

cofactor

A

Glycolysis II:

cofactor: none

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61
Q

Glycolysis IV:

cofactor

A

Glycolysis IV:

cofactor: none

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62
Q

Glycolysis V:

cofactor

A

Glycolysis V:

cofactor: none

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63
Q

Glycolysis VI:

reactant

A

Glycolysis VI: TWO RXNs PER GLYCOLYSIS I

reactant: Glyceraldehyde 3-phosphate (G3P) (x2)

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64
Q

Glycolysis VI:

product

A

Glycolysis VI: TWO RXNs PER GLYCOLYSIS I

product: 1,3-bsiphosphoglycerate (1,3-bPGA) (x2)

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65
Q

Glycolysis VI:

reactant

product

A

Glycolysis VI: TWO RXNs PER GLYCOLYSIS I

reactant: Glyceraldehyde 3-phosphate (G3P) (x2)
product: 1,3-bsiphosphoglycerate (1,3-bPGA) (x2)

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66
Q

Glycolysis VI:

type of reaction

A

Glycolysis VI: TWO RXNs PER GLYCOLYSIS I

type of reaction: Oxidation

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67
Q

Glycolysis VI:

enzyme

A

Glycolysis VI: TWO RXNs PER GLYCOLYSIS I

enzyme: Glyceraldehyde 3-phosphate dehydrogenase

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68
Q

Glycolysis VI:

cofactor

A

Glycolysis VI: TWO RXNs PER GLYCOLYSIS I

cofactor: Mg+, NAD+ + Pi (generally H2PO4) (+1 NADH + 1 H+) (x2 = +2 NADH + 2 H+)

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69
Q

Glycolysis VI:

reactant

product

type of reaction

enzyme

cofactor

A

Glycolysis VI: TWO RXNs PER GLYCOLYSIS I

reactant: Glyceraldehyde 3-phosphate (G3P) (x2)
product: 1,3-bsiphosphoglycerate (1,3-bPGA) (x2)

type of reaction: Oxidation

enzyme: Glyceraldehyde 3-phosphate dehydrogenase
cofactor: Mg+, NAD+ + Pi (generally H2PO4) ([+1 NADH + 1 H+] x2 = +2 NADH + 2 H+)

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70
Q

Structure of G3P

A

Glyceraldehyde 3-phosphate (G3P)

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71
Q

Structure of 1,3-bisphosphoglycerate

A

1,3-Bisphosphoglycerate (1,3-bPGA)

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72
Q

Structure and components of NAD+, site of reduction/oxidation(?) and number of electrons and protons transferred

A

Nicotinamide Adenine Dinucleotide (NAD+), reduced to NADH on the nicotinamide mononucleotide (NMN), picks up two electrons (one on N, one with H) and one proton

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73
Q

Structure of 1,3-bPGA

A

1,3-Bisphosphoglycerate (1,3-bPGA)

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74
Q

What is this catabolite, what reaction of glycolysis is it found in?

A

1,3-Bisphosphoglycerate (1,3-bPGA)

product of glycolysis VI

reactant in glycolysis VII

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75
Q

What is this catabolite, what reaction of glycolysis is it found in?

A

3-Phosphoglycerate (3-PGA)

product of glycolysis VII

reactant in glycolysis VIII

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76
Q

What is this catabolite, what reaction of glycolysis is it found in?

A

D-Glucose reactant in glycolysis I

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77
Q

What is this catabolite, what reaction of glycolysis is it found in?

A

Glucose 6-phosphate (G6P)

product of glycolysis I

reactant in glycolysis II

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78
Q

What is this catabolite, what reaction of glycolysis is it found in?

A

Fructose 6-phosphate

product of glycolysis II

reactant in glycolysis III

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79
Q

What is this catabolite, what reaction of glycolysis is it found in?

A

Fructose 1,6-bisphosphate

product of glycolysis III

reactant in glycolysis IV

80
Q

What is this catabolite, what reaction of glycolysis is it found in?

A

Dihydroxyacetone phosphate

product of glycolysis IV

reactant in glycolysis V

81
Q

What is this catabolite, what reaction of glycolysis is it found in?

A

Glyceraldehyde 3-phosphate (G3P)

product of glycolysis IV

product of glycolysis V

reactant in glycolysis VI

82
Q

What is this catabolite, what reaction of glycolysis is it found in?

A

2-Phosphoglycerate (2-PGA)

product of glycolysis VIII

reactant in glycolysis IX

83
Q

What is this catabolite, what reaction of glycolysis is it found in?

A

Phosphoenolpyruvate (PEP) product of glycolysis IX reactant in glycolysis X

84
Q

What is this catabolite, what reaction of glycolysis is it found in?

A

Pyruvate (Pyr) product of glycolysis X reactant in many other pathways including fermentation and oxidative phosphorylation

85
Q

What enzyme(s) cost ATP in glycolysis and with what step?

A

Hexokinase in glycolysis I as D-glucose is phosphorylated at position 6 (-1 ATP)

Phosphofructokinase 1 in glycolysis III as 6-phosphofructose is phosphorylated at position 1 (-1 ATP)

86
Q

What enzyme(s) generate ATP in glycolysis and with what step?

A

Phosphoglycerate kinase (PKG) in glycolysis VII as two 1,3-bisphosphoglycerate molecules are dephosphorylated to at position 1 (+2 ATP per glycolysis I)

Pyruvate kinase in glycolysis X as two phosphoenolpyruvate molecules are dephosphorylated to form two pyruvate molecules (+2 ATP per glycolysis I)

87
Q

What themes do you notice about the use and generation of ATP in glycolysis?

A

ATP is used in the first step and regenerated in the final step of glycolysis. Loss of ATP stems from phosphoryl transfers from ATP to the sugar using kinase. Gain of ATP stems from phosphoryl transfers from the sugar to ADP using kinase.

88
Q

Is D-glucose more oxidised or more reduced after glycolysis?

A

More oxidised. The ratio of O:C remains unchanged (1:1) but the ratio of H:C has decreased (from 2:1 to 1:1), meaning a loss of hydrogen (loss of H = oxidation)

89
Q

What is particular about the product of aldolase?

A

It produces two distinct products, a ketose (dihydrpxyacetone phosphate) and an aldose (G3P)

90
Q

Structure of 3-PGA

A

3-Phosphoglycerate (3-PGA)

91
Q

Structure of 3-phosphoglycerate

A

3-Phosphoglycerate (3-PGA)

92
Q

Structure of 2-PGA

A

2-Phosphoglycerate (2-PGA)

93
Q

Structure of 2-phosphoglycerate

A

2-Phosphoglycerate (2-PGA)

94
Q

Structure of PEP

A

Phosphoenolpyruvate (PEP)

95
Q

Structure of phosphoenolpyruvate

A

Phosphoenolpyruvate (PEP)

96
Q

Structure of pyruvate

A

Pyruvate (Pyr)

97
Q

Glycolysis VII:

reactant

A

Glycolysis VII: TWO RXNs PER GLYCOLYSIS I

reactant: 1,3-bisphosphoglycerate (1,3-bPGA) (x2)

98
Q

Glycolysis VII:

product

A

Glycolysis VII: TWO RXNs PER GLYCOLYSIS I

product: 3-Phosphoglycerate (3-PGA) (x2)

99
Q

Glycolysis VII:

reactant

product

A

Glycolysis VII: TWO RXNs PER GLYCOLYSIS I

reactant: 1,3-bisphosphoglycerate (1,3-bPGA) (x2)
product: 3-Phosphoglycerate (3-PGA) (x2)

100
Q

Glycolysis VII:

type of reaction

A

Glycolysis VII: TWO RXNs PER GLYCOLYSIS I

type of reaction: Phosphoryl transfer by kinase

101
Q

Glycolysis VII:

enzyme

A

Glycolysis VII: TWO RXNs PER GLYCOLYSIS I

enzyme: Phosphoglycerate kinase

102
Q

Glycolysis VII: cofactor

A

Glycolysis VII: TWO RXNs PER GLYCOLYSIS I

cofactor: Mg+, ADP (+1 ATP x2 = +2 ATP per glycolysis I)

103
Q

Glycolysis VII:

reactant

product

type of reaction

enzyme

cofactor

A

Glycolysis VII: TWO RXNs PER GLYCOLYSIS I

reactant: 1,3-bisphosphoglycerate (1,3-bPGA) (x2)
product: 3-Phosphoglycerate (3-PGA) (x2)

type of reaction: Phosphoryl transfer by kinase

enzyme: Phosphoglycerate kinase
cofactor: Mg+, ADP (+1 ATP x2 = +2 ATP per glycolysis I)

104
Q

Glycolysis VIII:

reactant

A

Glycolysis VIII: TWO RXNs PER GLYCOLYSIS I

reactant: 3-Phosphoglycerate (3-PGA) (x2)

105
Q

Glycolysis VIII:

product

A

Glycolysis VIII: TWO RXNs PER GLYCOLYSIS I

product: 2-Phosphoglycerate (2-PGA) (x2)

106
Q

Glycolysis VIII:

reactant

product

A

Glycolysis VIII: TWO RXNs PER GLYCOLYSIS I

reactant: 3-Phosphoglycerate (3-PGA) (x2)
product: 2-Phosphoglycerate (2-PGA) (x2)

107
Q

Glycolysis VIII:

type of reaction

A

Glycolysis VIII: TWO RXNs PER GLYCOLYSIS I

type of reaction: Phosphoryl shift by mutase

108
Q

Glycolysis VIII:

enzyme

A

Glycolysis VIII: TWO RXNs PER GLYCOLYSIS I

enzyme: Phosphoglycerate mutase

109
Q

Glycolysis VIII:

cofactor

A

Glycolysis VIII: TWO RXNs PER GLYCOLYSIS I

cofactor: none

110
Q

Glycolysis VIII:

reactant

product

type of reaction

enzyme

cofactor

A

Glycolysis VIII: TWO RXNs PER GLYCOLYSIS I

reactant: 3-Phosphoglycerate (3-PGA) (x2)
product: 2-Phosphoglycerate (2-PGA) (x2)

type of reaction: Phosphoryl shift by mutase

enzyme: Phosphoglycerate mutase
cofactor: none

111
Q

Glycolysis IX:

reactant

A

Glycolysis IX: TWO RXNs PER GLYCOLYSIS I

reactant: 2-Phosphoglycerate (2-PGA) (x2)

112
Q

Glycolysis IX:

product

A

Glycolysis IX: TWO RXNs PER GLYCOLYSIS I

product: Phosphoenolpyruvate (PEP) (x2)

113
Q

Glycolysis IX:

reactant

product

A

Glycolysis IX: TWO RXNs PER GLYCOLYSIS I

reactant: 2-Phosphoglycerate (2-PGA) (x2)
product: Phosphoenolpyruvate (PEP) (x2)

114
Q

Glycolysis IX:

type of reaction

A

Glycolysis IX: TWO RXNs PER GLYCOLYSIS I

type of reaction: Dehydration

115
Q

Glycolysis IX:

enzyme

A

Glycolysis IX: TWO RXNs PER GLYCOLYSIS I

enzyme: Enolase

116
Q

Glycolysis IX:

cofactor

A

Glycolysis IX: TWO RXNs PER GLYCOLYSIS I

cofactor: Mg+

117
Q

Glycolysis IX:

reactant

product

type of reaction

enzyme

cofactor

A

Glycolysis IX: TWO RXNs PER GLYCOLYSIS I

reactant: 2-Phosphoglycerate (2-PGA) (x2)
product: Phosphoenolpyruvate (PEP) (x2)

type of reaction: Dehydration

enzyme: Enolase
cofactor: Mg+

118
Q

Glycolysis X:

reactant

A

Glycolysis X: TWO RXNs PER GLYCOLYSIS I

reactant: Phosphoenolpyruvate (PEP) (x2)

119
Q

Glycolysis X:

product

A

Glycolysis X: TWO RXNs PER GLYCOLYSIS I

product: Pyruvate (Pyr) (x2)

120
Q

Glycolysis X:

reactant

product

A

Glycolysis X: TWO RXNs PER GLYCOLYSIS I

reactant: Phosphoenolpyruvate (PEP) (x2)
product: Pyruvate (Pyr) (x2)

121
Q

Glycolysis X:

type of reaction

A

Glycolysis X: TWO RXNs PER GLYCOLYSIS I

type of reaction: Phosphoryl transfer by kinase

122
Q

Glycolysis X:

enzyme

A

Glycolysis X: TWO RXNs PER GLYCOLYSIS I

enzyme: Pyruvate kinase

123
Q

Glycolysis X:

cofactor

A

Glycolysis X: TWO RXNs PER GLYCOLYSIS I

cofactor: Mg+, ADP (+1 ATP x2 = +2 ATP per glycolysis I)

124
Q

Glycolysis X: reactant product type of reaction enzyme cofactor

A

Glycolysis X: TWO RXNs PER GLYCOLYSIS I

reactant: Phosphoenolpyruvate (PEP) (x2)
product: Pyruvate (Pyr) (x2)

type of reaction: Phosphoryl transfer by kinase

enzyme: Pyruvate kinase
cofactor: Mg+, ADP (+1 ATP x2 = +2 ATP per glycolysis I)

125
Q

Phosphofructokinase 1

A

Adds a phosphate to fructose-6-phosphate (F6P) at C1 in glycolysis III. The key control point in controlling the rate of glycolysis.

Enzyme is elaborately regulated:

  • inhibited by high levels of ATP (why?) - this inhibition is reversed by high levels of AMP (why?)
  • inhibited by high levels of citrate (why?)
  • stimulated by fructose-2,6-bisphosphate (why?)

PFK1 is the most important control site in the mammalian glycolytic pathway. This step is subject to extensive regulation since it is not only highly exergonic under physiological conditions, but also because it is a committed step – the first irreversible reaction unique to the glycolytic pathway. This leads to a precise control of glucose and the other monosaccharides galactose and fructose going down the glycolytic pathway.

PFK1 is also inhibited by low pH levels which augment the inhibitory effect of ATP. The pH falls when muscle is functioning anaerobically and producing excessive quantities of lactic acid. This inhibitory effect serves to protect the muscle from damage that would result from the accumulation of too much acid.

PFK1 is allosterically inhibited by high levels of ATP but AMP reverses the inhibitory action of ATP. Therefore, the activity of the enzyme increases when the cellular ATP/AMP ratio is lowered. Glycolysis is thus stimulated when energy charge falls. PFK1 has two sites with different affinities for ATP which is both a substrate and an inhibitor.

Finally, PFK1 is allosterically inhibited by PEP, citrate, and ATP. Phosphoenolpyruvic acid is a product further downstream the glycolytic pathway. Although citrate does build up when the Krebs Cycle enzymes approach their maximum velocity, it is questionable whether citrate accumulates to a sufficient concentration to inhibit PFK-1 under normal physiological conditions. ATP concentration build up indicates an excess of energy and does have an allosteric modulation site on PFK1 where it decreases the affinity of PFK1 for its substrate. PFK1 is allosterically activated by a high concentration of AMP, but the most potent activator is fructose 2,6-bisphosphate, which is also produced from fructose-6-phosphate by PFK2. Hence, an abundance of F6P results in a higher concentration of fructose 2,6-bisphosphate (F-2,6-BP). The binding of F-2,6-BP increases the affinity of PFK1 for F6P and diminishes the inhibitory effect of ATP. This is an example of feedforward stimulation as glycolysis is accelerated when glucose is abundant. PFK is inhibited by glucagon through repression of synthesis. Glucagon activates protein kinase A which, in turn, shuts off the kinase activity of PFK2. This reverses any synthesis of F-2,6-BP from F6P and thus inhibits PFK1 activity. The precise regulation of PFK1 prevents glycolysis and gluconeogenesis from occurring simultaneously.

126
Q

PFK1 is inhibited by high levels of ATP, why?

A

ATP concentration build up indicates an excess of energy and does have an allosteric modulation site on PFK1 where it decreases the affinity of PFK1 for its substrate.

127
Q

PFK1 inhibition by ATP is reversed by AMP, why?

A

AMP reverses the inhibitory action of ATP. Therefore, the activity of the enzyme increases when the cellular ATP/AMP ratio is lowered. Glycolysis is thus stimulated when energy charge falls.

128
Q

PFK1 is inhibited by high levels of citrate, why?

A

Citrate builds up when the Krebs Cycle enzymes approach their maximum velocity

129
Q

PFK1 is stimulated by fructose 2,6-bisphosphate, why?

A

PFK1 is allosterically activated by a high concentration of AMP, but the most potent activator is fructose 2,6-bisphosphate, which is also produced from fructose-6-phosphate by PFK2. Hence, an abundance of F6P results in a higher concentration of fructose 2,6-bisphosphate (F-2,6-BP). The binding of F-2,6-BP increases the affinity of PFK1 for F6P and diminishes the inhibitory effect of ATP. This is an example of feedforward stimulation as glycolysis is accelerated when glucose is abundant.

130
Q

What enzyme is the first committed step of glycolysis and what step is it in?

A

Phosphofructokinase 1, glycolysis III

131
Q

What is the function of dehydrogenase enzymes in glycolysis?

A

Electrons move on hydrogens as a form of energy transfer. These are redox reactions where one species is gaining energy and one is losing.

132
Q

What step is 1,3 bisphosphoglycerate (1,3-bPGA) involved in and what does this say about its ∆G’°?

A

In glycolysis VII, a phosphate group is transferred to ADP to regenerate ATP. Because the ∆G’° for ADP to ATP is 30.5kJ/mol, the ∆G’° of 1,3-bPGA must release more than 30.5kJ/mol upon its conversion to 3-PGA to drive the condensation of ADP. The actual ∆G’° = 49.3kJ/mol for the phosphoryl group hydrolysis from 1,3-bPGA to 3-PGA. This is due to ionisation and subsequent resonance stabilisation of the carboxyl of 3-PGA.

133
Q

What is the difference between generation of ATP in glycolysis vs oxidative phosphorylation?

A

Glycolysis caries out substrate level phosphorylation using an intermediate with a very favourable hydrolysis and large ∆G’°. Oxidative phosphorylation uses the electron transport pathway which drives a proton gradient to make ATP.

134
Q

Explain how aldolase carries out a reaction with a large ∆G°’?

A

Two products are formed, a ketose and an alludes (dihydroxyacetone phosphate and glyceraldehyde 3-phosphate (G3P), respectively). The ketose is rapidly converted to the aldose form by Triose phosphate isomerase (glycolysis V), which is rapidly metabolised. This removal of products drives the reaction forward by making -RT ln Keq very negative, offsetting ∆G’°.

∆G = ∆G’° + RT ln Keq

135
Q

Free energy of hydrolysis of ATP to ADP

A

-30.5kJ/mol

136
Q

Which steps of glycolysis represent a drop in potential energy?

A

Glycolysis VI (creation of 2 NADH) Glycolysis VII (creation of 2 ATP) Glycolysis X (creation of 2 ATP)

137
Q

What step of glycolysis is this?

A

Glycolysis IV

138
Q

What step of glycolysis is this?

A

Glycolysis IV

139
Q

What step of glycolysis is this?

A

Glycolysis VI

140
Q

What step of glycolysis is this?

A

Glycolysis VII

141
Q

What step of glycolysis is this?

A

Glycolysis IX

142
Q

What step of glycolysis is this?

A

Glycolysis VIII

143
Q

What step of glycolysis is this?

A

Glycolysis X

144
Q

What enzyme carries out substrate level phosphorylation?

A

phosphoglycerate kinase (PGK)

Substrate level phosphorylation: A phosphate is transferred from a phosphorylated intermediate to ADP to make ATP.

145
Q

What are the three main fates of pyruvate?

A
146
Q

What are the four potential paths of pyruvate?

A
147
Q

What happens to pyruvate in anaerobic muslce?

A
148
Q

What two enzymes are linked by glycolysis and anaerobic respiration?

A

Lactate dehydrogenase, which converts pyruvate to L-lactate in anerobic respiration and glyceraldehyde 3-phosphate dehydrogenase, which converts G3P to 1,3-bPGA in step VI of glycolysis

Linked through NADH and the need to regenerate the oxdised form to continue glycolysis

149
Q

When glucose is converted to lactate, what is the net energy yield, in all forms? What enzymes catalyse these exchanges?

A

Anaerobic respiration: One glucose —–> Two lactate

ATP Investment:

Hexokinase: - 1 ATP

Phosphofructokinase: - 1 ATP

ATP Return:

Phosphoglycerate kinase: +2 ATP

Pyruvate kinase: +2 ATP

NAD+ No net change

150
Q

What happens to pyruvate in fermentation?

A

Pyruvate is converted to ethanol

151
Q

What two enzymes are linked by glycolysis and fermentation?

A

Alcoholdehydrogenase, which converts acetaldehyde to ethanol (EtOH) in fermentation and glyceraldehyde 3-phosphate dehydrogenase, which converts G3P to 1,3-bPGA in step VI of glycolysis

Linked through NADH and the need to regenerate the oxdised form to continue glycolysis

152
Q

What are the steps of fermentation?

A
153
Q

When glucose is converted to ethanol, what is the net energy yield, in all forms? What enzymes catalyse these exchanges?

A

fermentation: 1 glucose —–> 2 ethanol + 2 CO2

ATP Investment:

Hexokinase: - 1 ATP

Phosphofructokinase: -1 ATP

ATP Return:

Phosphoglycerate kinase: +2 ATP

Pyruvate kinase: +2 ATP

Net 2 ATP

NAD+ No net change

2 CO2 Generated

154
Q

What is different about fructose entering glycolysis compared to glucose? What is the same?

A

When fructose enters glycolysis, it has not been phosphorylated like the phosphofructo- intermediate (F6P) that begins step III of glycolysis. Thus, it is phosphorylated by fructokinase (instead of phosphofructokinase) into fructose-1-phosphate. This product is cleaved by fructose-1-phosphate aldolase, yeilding dihydroxyacetone phosphate (which heads into step V of glycolysis) and glyceraldehyde, which must be phosphorylated into G3P (glyceraldehyde-3-phosphate) by triose kinase to enter into step VI of glycolysis.

Both kinases (phosphorylating enzymes) require ATP, making the energy envestment of glucose and fructose the same.

155
Q

Structure of L-lactate

A
156
Q

What molecule is this? Where is it found in glycolysis?

A

Pyruvate (Pyr)

157
Q

What molecule is this? Where is it found in glycolysis?

A
158
Q

What part of pyruvate is modified to form lactate? What part is modified to form ethanol?

A

H & H+ are added across the carbonyl by lactate dehydrogenase to form L-lactate

The carboyl carbon is cleaved with both oxygens in the form of CO2 to form acetaldehyde by pyruvate decarboxylase, then H & H+ are added across the double bond of the carbonyl by alcohol dehydrogenase to form ethanol (EtOH)

159
Q

Pyruvate Fermentation I

reactant

A

Pyruvate Fermentation I

reactant: pyruvate (Pyr)

160
Q

Pyruvate Fermentation I

product

enzyme

cofactor

A

Pyruvate Fermentation I

product: Acetaldehyde

161
Q

Pyruvate Fermentation I

reactant

product

A

Pyruvate Fermentation I

reactant: pyruvate (Pyr)
product: Acetaldehyde

162
Q

Pyruvate Fermentation I

enzyme

cofactor

A

Pyruvate Fermentation I

enzyme: pyruvate decarboxylase

163
Q

Pyruvate Fermentation I

cofactor

A

Pyruvate Fermentation I

cofactor: TPP

releases CO2

<span>Thiamine pyrophosphate (TPP) is a thiamine (vitamin B1) derivative </span>

164
Q

Pyruvate Fermentation I

reactant

product

enzyme

cofactor

A

Pyruvate Fermentation I

reactant: pyruvate (Pyr)
product: Acetaldehyde
enzyme: pyruvate decarboxylase
cofactor: TPP

releases CO2

165
Q

What is this?

A

Acetaldehyde

166
Q

What is the structure of acetaldehyde?

A
167
Q

TPP

A

Thiamine pyrophosphate (TPP) a thiamine (vitamin B1) derivative which is a cofactor that is present in all living systems, in which it catalyzes several biochemical reactions. It is an essential nutrient (vitamin) in humans.

TPP works as a coenzyme in many enzymatic reactions, such as:

Pyruvate dehydrogenase complex

Pyruvate decarboxylase in ethanol fermentation

Alpha-ketoglutarate dehydrogenase complex

Branched-chain amino acid dehydrogenase complex

2-hydroxyphytanoyl-CoA lyase

Transketolase

168
Q

Pyruvate Fermentation II

reactant

A

Pyruvate Fermentation II

reactant: acetaldehyde

169
Q

Pyruvate Fermentation II

product

A

Pyruvate Fermentation II

reactant: acetaldehyde
product: ethanol (EtOH)
enzyme: alcohol dehydrogenase
cofactor: NADH

170
Q

Pyruvate Fermentation II

reactant

product

A

Pyruvate Fermentation II

reactant: acetaldehyde
product: ethanol (EtOH)

171
Q

Pyruvate Fermentation II

enzyme

A

Pyruvate Fermentation II

enzyme: alcohol dehydrogenase

172
Q

Pyruvate Fermentation II

cofactor

A

Pyruvate Fermentation II

cofactor: NADH

173
Q

Pyruvate Fermentation II

reactant

product

enzyme

cofactor

A

Pyruvate Fermentation II

reactant: acetaldehyde
product: ethanol (EtOH)
enzyme: alcohol dehydrogenase
cofactor: NADH

174
Q

Structure of lactose

A
175
Q

What does lactose break down into initially?

A

D-galactose and D-glucose

176
Q

What breaks down lactose in the body?

A

Lactase (β-D-galactosidase)

177
Q

What relation is D-galactose to D-glucose?

A

Galactose is a 4-epimer of glucose

178
Q

Galactose into glycolysis I

reactant

A

Galactose into glycolysis I

reactant: D-galactose

179
Q

Galactose into glycolysis I

product

A

Galactose into glycolysis I

product: galactose-1-phosphate

180
Q

Galactose into glycolysis I

enzyme

cofactor

A

Galactose into glycolysis I

enzyme: galactokinase

181
Q

Galactose into glycolysis I

reactant

product

A

Galactose into glycolysis I

reactant: D-galactose
product: galactose-1-phosphate

182
Q

Galactose into glycolysis I

cofactor

A

Galactose into glycolysis I

cofactor: ATP

183
Q

Galactose into glycolysis I

reactant

product

enzyme

cofactor

A

Galactose into glycolysis I

reactant: D-galactose
product: galactose-1-phosphate
enzyme: galactokinase
cofactor: ATP

184
Q

Galactose into glycolysis II

reactant

A

Galactose into glycolysis II

reactant: galactose-1-phosphate, UDP-glucose

185
Q

Galactose into glycolysis II

product

A

Galactose into glycolysis II

product: glucose-1-phosphate, UDP-galactose

186
Q

Galactose into glycolysis II

reactant

product

A

Galactose into glycolysis II

reactant: galactose-1-phosphate, UDP-glucose
product: glucose-1-phosphate, UDP-galactose

187
Q

Galactose into glycolysis II

enzyme

A

Galactose into glycolysis II

enzyme: galactose-1-phosphate uridylyltransferase

188
Q

Galactose into glycolysis II

cofactor

A

Galactose into glycolysis II

cofactor: none

189
Q

Galactose into glycolysis II

reactant

product

enzyme

cofactor

A

Galactose into glycolysis II

reactant: galactose-1-phosphate, UDP-glucose
product: glucose-1-phosphate, UDP-galactose
enzyme: galactose-1-phosphate uridylyltransferase
cofactor: none

190
Q

How do you convert UDP-galactose into UDP-glucose?

A
191
Q

Galactose into glycolysis III

reactant

A

Galactose into glycolysis III

reactant: glucose-1-phosphate

192
Q

Galactose into glycolysis III

product

A

Galactose into glycolysis III

product: glucose-6-phosphate

193
Q

Galactose into glycolysis III

reactant

product

A

Galactose into glycolysis III

reactant: glucose-1-phosphate
product: glucose-6-phosphate

194
Q

Galactose into glycolysis III

enzyme

A

Galactose into glycolysis III

enzyme: phosphoglucomutase

195
Q

Galactose into glycolysis III

cofactor

A

Galactose into glycolysis III

cofactor: none

196
Q

Galactose into glycolysis III

reactant

product

enzyme

cofactor

A

Galactose into glycolysis III

reactant: glucose-1-phosphate
product: glucose-6-phosphate
enzyme: phosphoglucomutase
cofactor: none

BIOC 4331 (19 decks)

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