Lecture 6: Glycolysis: Enzymatic Reactions

Question 1

glycolysis pathway

Answer 1

ANAEROBIC

doesnt need oxygen

Question 2

what does gycolysis do?

Answer 2

cleaves glucose into 2 pyruvates

net yeild of 2ATP

Question 3

what are the two stages of glycolysis

Answer 3

ATP investment stage

ATP earning stage

Question 4

glucose chemical equation

Answer 4

C6H12O6

Question 5

pyruvate chemical equation

Answer 5

C3H3O3

Question 6

What do they 3 enzymes do (boradly)

Answer 6

catalyze very exergonic reactions (irreversible)

these drive metabolic flux

Question 7

Substrate level phosphorylation

Answer 7

use phosphoryl transfer rxns independent of mitochondrial ATP synthase complex

directly phosphorylaye ADP to make ATP

2 happen in glycolysis

Question 8

Facts about glycolysis and its importance in nature

Answer 8

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!!!!!

Question 9

What does glycolysis accomplish for the cell?

Answer 9

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

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

Question 10

Overall net reaction of glycolysis?

Answer 10

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

deltaG^0’=-35.5kJ/mol

Question 11

WHat are the key regulated enzymes in glycolysis?

Answer 11

Hexokinase
Phosphofructokinase-1
Pyruvate Kinase

Question 12

What are examples of glycolysis in real life?

Answer 12

anaerobic conditions

intense exercise

Question 13

where does glycolysis take place?

Answer 13

in the cytosol!

Question 14

where is bulk of ATP generated

Answer 14

in mitochondria

by oxidative phosphorylation

Question 15

chem equation for complete glucose oxidation

Answer 15

Glucose+ 6O2–> 6CO2 + 6H2O

deltaG^0’=+30.5kJ/mol

Question 16

Theoretical Max yield of glucose oxidation vs. actual yield

Answer 16

90 ATP/Glucose
actual is 32 ATP/glucose

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

Question 17

what does glycolysis MEAN?``

Answer 17

splitting of glucose

glucose used to be called glycos

Question 18

net loss in glycolysis??

Answer 18

NO net loss of carbon or oxygen atoms

Question 19

First stage of glycolysis overview

Answer 19

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

TWO ATP USED

Question 20

listen to slide 9

Answer 20

listen to slide 9

Question 21

what we end up with

Answer 21

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

Question 22

Second Stage of Glycolysis overview

Answer 22

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

Question 23

ATP tields from stage 2

Answer 23

4 TOTAL ATP

2 NET ATP

Question 24

look at slide 11 a lot

Answer 24

look at slide 11 a lot

Question 25

what does NADH do?

Answer 25

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

Question 26

Large negative delta G and delta G^0' values

Answer 26

irreversible under actual conditions | favorable under actual conditions

Question 27

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

Answer 27

actual conditions in cell can influence directionality of reaction

Question 28

Reaction 1

Answer 28

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

Question 29

Reaction 2

Answer 29

Isomerization of glucose-6-P to fructose-6-P catalyzed by phosphoglucose isomerase directionality depends on metabolite concs (very small delta G change)

Question 30

Reaction 3

Answer 30

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

Question 31

Reaction 4

Answer 31

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!

Question 32

Reaction 5

Answer 32

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!

Question 33

Reaction 6

Answer 33

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

Question 34

NAD+ regeneration for reaction 6

Answer 34

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)

Question 35

Reaction 7

Answer 35

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)

Question 36

substrate level phosphorylation means....

Answer 36

using molecules to make ATP generate ATP INDEPENDENT of ATP synthase need a substrate that has a higher phosphoryl transfer potential than ATP?

Question 37

Reaction 8

Answer 37

phosphoryl shift by phosphoglycerate mutase convert 3-phospoglycerate to 2-phosphoglycerate move the phosphate group directionality depends on metabolite concs

Question 38

Reaction 9

Answer 38

``` 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

Question 39

Reaction 10

Answer 39

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)