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Cellular Respiration Stage 1: Glycolysis (adapted from K. Foglia). What’s the point?. The point is to make ATP !. ATP. glucose      pyruvate. 6C. 3C. 2 x. Glycolysis. Breaking down glucose “ glyco – lysis ” (splitting sugar) ancient pathway which harvests energy

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Cellular Respiration Stage 1: Glycolysis (adapted from K. Foglia)

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Cellular respiration stage 1 glycolysis adapted from k foglia

Cellular RespirationStage 1: Glycolysis(adapted from K. Foglia)


Cellular respiration stage 1 glycolysis adapted from k foglia

What’s thepoint?

The pointis to makeATP!

ATP


Glycolysis

glucose      pyruvate

6C

3C

2x

Glycolysis

  • Breaking down glucose

    • “glyco – lysis” (splitting sugar)

    • ancient pathway which harvests energy

      • where energy transfer first evolved

      • still is starting point for ALL cellular respiration

    • but it’s inefficient

      • generate only2 ATP for every 1 glucose

    • occurs in cytoplasm

In thecytosol?Why doesthat makeevolutionarysense?


Evolutionary perspective

Evolutionary perspective

Enzymesof glycolysis are“well-conserved”

  • Prokaryotes

    • first cells had no organelles

  • Anaerobic atmosphere

    • life on Earth first evolved withoutfree oxygen (O2) in atmosphere

    • energy had to be captured from organic molecules in absence of O2

  • Prokaryotes that evolved glycolysis are ancestors of all modern life

    • ALL cells still utilize glycolysis

You meanwe’re related?Do I have to invitethem over for the holidays?


Overview

enzyme

enzyme

enzyme

enzyme

enzyme

enzyme

enzyme

enzyme

ATP

ATP

4

2

4

2

2

ADP

NAD+

ADP

2Pi

2

2H

2Pi

glucose

C-C-C-C-C-C

Overview

The reactions

  • convert glucose (6C)to 2 pyruvate (3C)

  • produces:

    4 ATP & 2 NADH

  • consumes: 2 ATP

  • NET yield:

    2 ATP & 2 NADH

fructose-1,6bP

P-C-C-C-C-C-C-P

DHAP

P-C-C-C

G3P

C-C-C-P

pyruvate

C-C-C

DHAP = dihydroxyacetone phosphate

G3P = glyceraldehyde-3-phosphate


Glycolysis summary must know this

Glycolysis summary (MUST KNOW THIS)

endergonic

invest some ATP

ENERGY INVESTMENT

-2 ATP

G3P

C-C-C-P

exergonic

harvest a little ATP & a little NADH

ENERGY PAYOFF

4 ATP

like $$in the bank

  • net yield

  • 2 ATP

  • 2 NADH

NET YIELD


1st half of glycolysis 5 reactions nice to know

1st half of glycolysis (5 reactions) (nice to know)

CH2OH

Glucose “priming”

O

Glucose

1

ATP

hexokinase

  • get glucose ready to split

    • phosphorylate glucose

    • molecular rearrangement

  • split destabilized glucose

ADP

CH2

O

P

O

Glucose 6-phosphate

2

phosphoglucose

isomerase

CH2

P

O

CH2OH

O

Fructose 6-phosphate

3

ATP

phosphofructokinase

P

O

CH2

CH2

O

P

O

ADP

Fructose 1,6-bisphosphate

aldolase

4,5

H

O

CH2

P

isomerase

C

O

C

O

Dihydroxyacetone

phosphate

Glyceraldehyde 3

-phosphate (G3P)

CHOH

CH2OH

CH2

O

P

NAD+

Pi

NAD+

Pi

6

glyceraldehyde

3-phosphate

dehydrogenase

NADH

NADH

P

O

O

CHOH

1,3-Bisphosphoglycerate

(BPG)

1,3-Bisphosphoglycerate

(BPG)

CH2

O

P


2nd half of glycolysis 5 reactions nice to know and just look at

2nd half of glycolysis (5 reactions) (nice to know and just look at )

DHAP

P-C-C-C

G3P

C-C-C-P

Energy Harvest

  • NADH production

    • G3P donates H

    • oxidizes the sugar

    • reduces NAD+

    • NAD+ NADH

  • ATP production

    • G3P    pyruvate

    • PEP sugar donates P

      • “substrate level phosphorylation”

    • ADP  ATP

Pi

Pi

NAD+

NAD+

6

NADH

NADH

7

ADP

ADP

O-

phosphoglycerate

kinase

C

ATP

ATP

CHOH

3-Phosphoglycerate

(3PG)

3-Phosphoglycerate

(3PG)

CH2

P

O

8

O-

phosphoglycero-mutase

O

C

H

C

O

P

2-Phosphoglycerate

(2PG)

2-Phosphoglycerate

(2PG)

CH2OH

O-

9

H2O

H2O

enolase

C

O

O

C

P

Phosphoenolpyruvate

(PEP)

Phosphoenolpyruvate

(PEP)

CH2

O-

10

ADP

ADP

C

O

pyruvate kinase

Payola!Finally some ATP!

ATP

ATP

C

O

CH3

Pyruvate

Pyruvate


Substrate level phosphorylation

O-

9

H2O

H2O

enolase

C

O

O

C

P

Phosphoenolpyruvate

(PEP)

Phosphoenolpyruvate

(PEP)

CH2

O-

10

ADP

ADP

C

O

pyruvate kinase

ATP

ATP

C

O

CH3

Pyruvate

Pyruvate

Substrate-level Phosphorylation

  • In the last steps of glycolysis, where did the P come from to make ATP?

    • the sugar substrate (PEP)

  • P is transferred from PEP to ADP

    • kinase enzyme

    • ADP  ATP

ATP

I get it!

The Pi camedirectly fromthe substrate!


Energy accounting of glycolysis must know

2 ATP

2 ADP

2 NAD+

4 ADP

ATP

4

2

Energy accounting of glycolysis (must know)

  • Net gain = 2 ATP + 2 NADH

    • some energy investment (-2 ATP)

    • small energy return (4 ATP + 2 NADH)

  • One 6C sugar Two 3C sugars

glucose      pyruvate

6C

3C

2x

All that work! And that’s all I get?

Butglucose hasso much moreto give!


Is that all there is

O2

O2

O2

O2

O2

3C

2x

Is that all there is?

  • Not a lot of energy…

    • for 1 billon years+ this is how life on Earth survived

      • no O2 = slow growth, slow reproduction

      • only harvest 3.5% of energy stored in glucose

        • more carbons to strip off = more energy to harvest

glucose     pyruvate

6C

Hard wayto makea living!


But can t stop there

But can’t stop there!

  • Going to run out of NAD+

    • without regenerating NAD+,energy production would stop!

    • another molecule must accept H from NADH

      • so NAD+ is freed up for another round

raw materialsproducts

Glycolysis

glucose + 2ADP + 2Pi + 2 NAD+2pyruvate+2ATP+2NADH


How is nadh recycled to nad

recycleNADH

How is NADH recycled to NAD+?

without oxygen

anaerobic respiration

“fermentation”

with oxygen

aerobic respiration

Another molecule must accept H from NADH

pyruvate

NAD+

H2O

CO2

ETC

NADH

NADH

O2

acetaldehyde

NADH

acetyl-CoA

NAD+

NAD+

lactate

lactic acidfermentation

which path you use depends on who you are…

Krebs

cycle

ethanol

alcoholfermentation


Fermentation anaerobic

pyruvate  ethanol + CO2

3C

2C

1C

pyruvate  lactic acid

NADH

NADH

NAD+

NAD+

3C

3C

Fermentation (anaerobic)

  • Bacteria, yeast

back to glycolysis

  • beer, wine, bread

  • Animals, some fungi

back to glycolysis

  • cheese, anaerobic exercise (no O2)


Alcohol fermentation

pyruvate  ethanol + CO2

3C

2C

1C

NADH

NAD+

recycleNADH

bacteria yeast

Alcohol Fermentation

back to glycolysis

  • Dead end process

    • at ~12% ethanol, kills yeast

    • can’t reverse the reaction

Count thecarbons!


Lactic acid fermentation

O2

pyruvate  lactic acid

NADH

NAD+

3C

3C

recycleNADH

animalssome fungi

Lactic Acid Fermentation

Go back to glycolysis

  • Reversible process

    • once O2 is available, lactate is converted back to pyruvate by the liver

Count thecarbons!


Pyruvate is a branching point

O2

O2

Pyruvate is a branching point

Pyruvate

fermentation

anaerobicrespiration

mitochondria

Krebs cycle

aerobic respiration


Cellular respiration stage 1 glycolysis adapted from k foglia

NO!There’s still more to my story!

Any Questions?


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