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Biochemistry > 9.3 Glycolysis Pathway > Flashcards

9.3 Glycolysis Pathway Flashcards

1
Q

what is the primary pathway for ATP production under anaeroboic conditions and in cells lacking mitochondria?

A

glycolysis

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2
Q

where does glycolysis take place?

A

in the cytosol

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3
Q

what 4 reactants does glycolysis use?

A

1 glucose, 2 NAD+, 2 ADP, 2 Pi

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4
Q

what 5 products does glycolysis generate?

A

2 pyruvates, 2 NADH, 2 H+, 2 ATP, 2 H20

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5
Q

what does the glucose in glycolysis generate?

A

2 pyuvates

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6
Q

what does the NAD+ in glycolysis generate?

A

2 NAD+ make 2 NADH and 2 H+

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7
Q

what do the 2 ADP and 2 Pi of glycolysois generate?

A

2 ATP

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8
Q

give the overall reaction equation of glycolysis

A

glucose + 2 NAD+ + 2 ADP + 2Pi double arrow (reversibly yield) 2 pyruvate + 2 NADH + 2 H+ + 2 ATP + 2 H2O

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9
Q

what is the overall energy of the glycolysis reaction? what does this mean in terms of the steps

A

overall is -2,850 kj/mol which is hella energy and since cells are not large enough, energy would be wasted if all done at once, so the reaction is broken down into smaller steps for more efficient energy usage

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10
Q

what are the 2 stages of glycolysis?

A

stage 1: 5 steps of investing ATP
stage 2: 5 steps of earning ATP

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11
Q

what do kinases do? how are they used in glycolysis?

A

transfer a phosphate group between ATP and another substrate; used in glycolysis to make or consume ATP

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12
Q

what do isomerases do? how are they used in glycolysis?

A

change the structure of a substrate while the molecular formula remains the same; used in glycolysis to create isomers

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13
Q

what dp phosphatases do? how are they used in glycolysis?

A

remove a phosphate group from a substrate without using ATP; used in glycolysis to release Pi

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14
Q

list 6 classes of enzymes involved in glycolysis

A
  1. kinases
  2. isomerase
  3. phosphatases
  4. aldolases
  5. mutases
  6. enolases
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15
Q

what is consumed in stage 1 of glycolysis?

A

2 ATP

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16
Q

what does stage 1 of glycolysis create and produce? (2)

A
  1. negatively charged molecules that can’t diffuse out of the cell
  2. produces 2 glyceraldehyde-3-phosphates for stage 2
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17
Q

what are the most important steps of stage 1 of glycolysis and why? (be able to list them out here)

A

steps 1 and 3 because they are irreversible and consume ATP

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18
Q

what is reaction 1 of glycolysis?

A

glucose and ATP are converted to glucose-6 phosphate and ADP by either hexokinase (in body cells) or glucokinase (in pancreas and liver cells)

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19
Q

what happens structurally in reaction 1 of glycolysis?

A

a phosphate group is added to C6 of glucose

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20
Q

list 4 key points of reaction 1 of glycolysis

A
  1. it is irreversible because delta G is very negative! (single arrow in rxn)
  2. 1 ATP is consumed (out of 2 in this stage)
  3. phosphorylation precents glucose from leaving the cell
  4. Mg2+ is required for all kinase reactions to shield negative charges
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21
Q

how does glucose-6-phosphate inhibit hexokinase? what does this mean?

A

G6P binds to hexokinase and inhibits ATP binding by allosteric regulation; means that the 1st step of glycolysis can be regulated by product inhibition feedback

22
Q

what is reaction 2 of glycolysis?

A

glucose-6-phosphate is converted to fructose-6-phosphate by phosphpglucose isomerase

23
Q

what happens structurally during reaction 2 of glycolysis?

A

the six-membered ring is converted to a 5-membered ring and the carbonyl is moved from C1 to C2

24
Q

what is a key point about the activation energy of reaction 2 of glycolysis?

A

it occurs near equilibrium (low activation energy) so it is a concentration-driven reaction

25
Q

what happens in reaction 3 of glycolysis?

A

fructose-6-phosphate and ATP are converted to phosphofructokinase-1 (PFK-1) and ADP by fructose-1,6-bisphosphate

26
Q

what happens structurally in reaction 3 of glycolysis?

A

the OH is removed from C1 and a phosphate group is added to C1

27
Q

list 4 key points about reaction 3 of glycolysis

A
  1. it is irreversible!! (single arrow!)
  2. 1 ATP is consumed
  3. allosterically regulated by energy charge
  4. rate limiting step for the entire glycolysis pathway!!!
28
Q

list 3 activators of PFK-1 and a commonality among them

A
  1. AMP
  2. ADP
  3. fructose-2,6-bisphosphate
    (all signal low energy charge within cell, activate to get glycolysis going to get more energy)
29
Q

list 2 inhibitors of PFK-1

A
  1. phosphoenolpyruvate
  2. ATP
30
Q

what happens in reaction 4 of glycolysis?

A

fructose-1,6-bisphosphate is converted to dihydroxyacetone phosphate and glyceradehyde-3-phosphate by aldolase

31
Q

what happens structurally in reaction 4 of glycolysis?

A

our 5-membered ring is split open to yield the two products, each with their own phosphate group

32
Q

list 3 key points about reaction 4 of glycolysis

A
  1. low activation energy, occurs near equilibrium, concentration driven
  2. reverse aldo condensation
  3. cellular metabolist concentrations favor forward reaction
33
Q

what happens in reaction 5 of glycolysis?

A

dihydroxyacetone phosphate is converted to another glyceraldehyde-3-phosphate by triose phosphate isomerse, with an enediol intermediate

34
Q

list 3 key points about reaction 5 of glycolysis

A
  1. the activation energy is low, equilibrium, concentration driven
  2. both products from reaction 4 enter the pathway
  3. products of reaction 5 are quickly removed in steps 6 and 7
35
Q

describe stage 2 of glycolysis

A
  1. 2 G3Ps enter
  2. 4 ATP produced
  3. 2 NADH produced
  4. 2 H+ produced
  5. reaction 10 is irreversible!!
36
Q

whawhat is the net ATP gain of glycolysis and why?

A

net gain of 2; although 4 are produced in stage 2, 2 are invested in stage 1

37
Q

what is important to remember about the reactants and products of stage 2 of glycolysis?

A

everything happens twice! because 2 G3P enter!!

38
Q

what happens in reaction 6 of glycolysis?

A

2 G3P, 2 NAD+,and 2 Pi are converted to 2 1,3-bisphosphoglycerates, 2 NADH, and 2 H+ by glyceraldehyde-3-phosphate dehydrogenase

39
Q

what happens structurally in reaction 6 of glycolysis

A

remove an H from G3Ps, use it to reduce NAD+, and add phosphate groups to the G3Ps

40
Q

list 3 key points of reaction 6 of glycolysis

A
  1. 2 NADH produced
  2. oxidation of C1
  3. product quickly consumed, reaction is coupled with step 7 so concentration favors the forward reaction
41
Q

what happens in reaction 7 of glycolysis?

A

2 1,3-bisphosphoglycerates and 2 ADPs are converted to 2 3-phosphpglycerates and 2 ATPs byy phosphoglycerate kinase

42
Q

what happens structurally in reaction 7 of glycolysis?

A

the phosphate groups are removed from the 1,3-bisphosphoglycerates and added to the ADPs to form 2 ATPs

43
Q

list 3 key points about reaction 7 of glycolysis

A
  1. 2 ATP produced
  2. reaction is coupled with step 6
  3. intermediate is 2,3-bisphosphoglycerate
44
Q

describe the side reaction that occurs in reaction 7 of glycolysis erythrocytes

A

2 1,3-bisphosphoglycerates are converted to 2 2,3-BPGs!!! by bisphosphoglycerate mutase, which as we know decreases binding of O2 and loows RBCs to deliver their O2!!; then is converted to 3-phosphoglycerate in regular reaction 7

45
Q

what happens in reaction 8 of glycolysis?

A

2 3-phosphoglycerates are converted to 2 2-phosphoglycerates by phosphoglycerate mutase

46
Q

what happens structurally in reaction 8 of glycolysis

A

the phosphate group is shifted from C3 to C2

47
Q

what happens in reaction 9 of glycolysis?

A

2 2-phosphoglycerates aare converted to 2 phsophoenolpyruvates (PEPs) and 2 H2Os by enolase

48
Q

what happens structurally in reaction 9 of glycolysis?

A

a dehydration reaction occurs to remove 2 H and 1 O for the H2O release

49
Q

what happens in reaction 10 of glycolysis?

A

2 PEPs and 2 ADPs are converted to 2 pyruvates and 2 ATPs by pyruvate kinase

50
Q

what happen structurally in reaction 10 of glycolysis?

A

the phosphate groups are removed from PEPs and added to ADPs to form ATPs

51
Q

list 3 key points about reaction 10 of glycolysis

A
  1. irreversible!!! single arrow in rxn!!
  2. 2 ATP produced
  3. is actually 2 coupled reactions of PEP to enolpyruvate to pyruvate

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