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Biochem 385 Unit 1 > Lecture 6: Glycolysis: Enzymatic Reactions > Flashcards

Lecture 6: Glycolysis: Enzymatic Reactions Flashcards

1
Q

glycolysis pathway

A

ANAEROBIC

doesnt need oxygen

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2
Q

what does gycolysis do?

A

cleaves glucose into 2 pyruvates

net yeild of 2ATP

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3
Q

what are the two stages of glycolysis

A

ATP investment stage

ATP earning stage

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4
Q

glucose chemical equation

A

C6H12O6

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5
Q

pyruvate chemical equation

A

C3H3O3

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6
Q

What do they 3 enzymes do (boradly)

A

catalyze very exergonic reactions (irreversible)

these drive metabolic flux

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7
Q

Substrate level phosphorylation

A

use phosphoryl transfer rxns independent of mitochondrial ATP synthase complex

directly phosphorylaye ADP to make ATP

2 happen in glycolysis

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8
Q

Facts about glycolysis and its importance in nature

A

1) ancient, it evolved very early on
2) primary way to make ATP under anaerobic conditions (also in cells lacking mitochondria)

3) Metabolites of glycolysis are precursors for interependent patways (like mitochondrial ATP synth)
ex) pyruvate!!!!!

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9
Q

What does glycolysis accomplish for the cell?

A

generates 2ATP/glucose (small amount) (crit for anaerobic condtions)

generates pyruvate (used to make acetyl-CoA
also lactate and sometimes ethanol
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10
Q

Overall net reaction of glycolysis?

A

Glucose+ 2NAD + 2ADP +2Pi–> 2 pyruvate + 2NADH +2H+ + 2 ATP +2H2O

deltaG^0’=-35.5kJ/mol

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11
Q

WHat are the key regulated enzymes in glycolysis?

A

Hexokinase
Phosphofructokinase-1
Pyruvate Kinase

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12
Q

What are examples of glycolysis in real life?

A

anaerobic conditions

intense exercise

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13
Q

where does glycolysis take place?

A

in the cytosol!

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14
Q

where is bulk of ATP generated

A

in mitochondria

by oxidative phosphorylation

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15
Q

chem equation for complete glucose oxidation

A

Glucose+ 6O2–> 6CO2 + 6H2O

deltaG^0’=+30.5kJ/mol

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16
Q

Theoretical Max yield of glucose oxidation vs. actual yield

A

90 ATP/Glucose
actual is 32 ATP/glucose

why so different?
because some energy is lost as heat!!!!!

17
Q

what does glycolysis MEAN?``

A

splitting of glucose

glucose used to be called glycos

18
Q

net loss in glycolysis??

A

NO net loss of carbon or oxygen atoms

19
Q

First stage of glycolysis overview

A

ATP investment (in steps 1 and 3)
generate GAP
GAP oxidized to produce NADH and 1,3-bisphophoglycerate

TWO ATP USED

20
Q

listen to slide 9

A

listen to slide 9

21
Q

what we end up with

A

from 1 6-carbon molec to 2 3-carbon molecs (made identical in step 5?)

22
Q

Second Stage of Glycolysis overview

A

we get energy back
Remember, each reaction happens TWICE, once on each of the 3-carbon molecules

from each glucose molecule, we get TWO pyruvate molecules

23
Q

ATP tields from stage 2

A

4 TOTAL ATP

2 NET ATP

24
Q

look at slide 11 a lot

A

look at slide 11 a lot

25
Q

what does NADH do?

A

NADH is the source of reducing power for the cell

we need a molec of NAD+ to reduce every time we oxidize GAP

NAD+ is regenerated from the metabolism of pyruvate

26
Q

Large negative delta G and delta G^0’ values

A

irreversible under actual conditions

favorable under actual conditions

27
Q

delta G^0’ and delta values that are close to 0 (pos or neg, -2.5 or +1.7 for ex)

A

actual conditions in cell can influence directionality of reaction

28
Q

Reaction 1

A

phosphorylation of glucose by hexokinase or glucokinase

use of ATP to phosphorylate glucose

GLUCOSE CANNOT LEAVE CELL AFTER ITS BEEN PHOSPHORYLATED

helps keep it in the cell so it can be used for the rest of the reaction

hexokinase is in all cells, glucokinase pretty much just liver and pancreas

29
Q

Reaction 2

A

Isomerization of glucose-6-P to fructose-6-P
catalyzed by phosphoglucose isomerase

directionality depends on metabolite concs (very small delta G change)

30
Q

Reaction 3

A

phosphorylation of fructose-6-P to fuctose1,6-BP

use phosphofucktokinase 1

irreversible
***one of key regulated steps!!!!
control how much you commit to glycolysis pathway
b/c ATP being used, we don’t want to use ATP if we don’t have to. don’t want to be wasteful

31
Q

Reaction 4

A

cleavage of fructose-1,6-BP by aldolase to make glyceraldehyde-3-+ and dihydroxyacetone-P

this is where we make the 6-carbon molecule two 3-carbon molecules

directionality of rxn depends on metabolite concs!

32
Q

Reaction 5

A

Isomerization of dihydroxyacetone-P to GAP

use triose phosphate isomerase

step that makes DHAP into GAP so that we have 2 identical GAP molecules! (now we can procede with identical reaction in the rest of the pathway)

directionality depends on metabolite concs!

33
Q

Reaction 6

A

oxidation and phosphorylation of glyceraldehyde-3-P to make 1,3 bisphosphoglycerate

use glyceraldehyde-3-P dehydrogenase

Need CONSTANT supply of (oxidized) NAD+

NAD+- reduced to NADH

34
Q

NAD+ regeneration for reaction 6

A

AEROBIC: NADH formed in glycolysis transfers electrons to O2 through ETC (acetyl coA from pyruvate goes on to the ETC).
ANAEROBIC: NAD+ regenerated by reduction of pyruvate to lactate or ethanol(fermentation)

35
Q

Reaction 7

A

Generation of ATP from 1,3-biphosphoglycerate to 3-phosphoglycerate

done by phosphoglycerate kinase

Substrate level phosphorylation
in this case, the phosphase donor 1,3-BGP is a substrae with high phosphoryl-transfer potential

this compound has HIGHER phosphoryl transfer potential than ATP, so it can be used to directly phosphorylate ADP to make ATP

WE HAVE used 2 ATP (in phase one) and we just made 2 ATP (remember, one per each 3-carbon molec)

36
Q

substrate level phosphorylation means….

A

using molecules to make ATP
generate ATP INDEPENDENT of ATP synthase

need a substrate that has a higher phosphoryl transfer potential than ATP?

37
Q

Reaction 8

A

phosphoryl shift by phosphoglycerate mutase
convert 3-phospoglycerate to 2-phosphoglycerate

move the phosphate group

directionality depends on metabolite concs

38
Q

Reaction 9

A 
dehydration of 2-hposphoglycerate by enolase
forms phospoenolpyruvate (PEP)

make an enol containing compound

phosphate ester of alcohol has LOW phosphoryl transfer potential, won’t work to phosphorylate ADP
instead, use enol phosphate, which has HIGH phosphoryl-transfer potential

direction depends on metabolite concs

39
Q

Reaction 10

A

GENERATION OF ATP
by pyruvate kinase
when phosphoenolpyruvate is converted to pyruvate

substrate level phosphorylation generates ATP (independednt of ATP synthase)

ATP and Pyruvate are final products)

Biochem 385 Unit 1 (13 decks)

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