Cellular RespirationHarvesting Chemical Energy

2006-2007

Cellular RespirationStage 1:

Glycolysis

Modified from Kim Foglia

TUESDAY, NOV. 12TH

Today I will…1. Describe the process of glycolysis.2. State the reactants and products of glycolysis.

The Point is to Make ATP!

2006-2007

ATP

What’s the point?

glucose pyruvate2x6C 3C

Breaking down glucose ◦ “glyco – lysis” (splitting sugar)

◦ most ancient form of energy capture starting point for all cellular respiration

◦ inefficient generate only 2 ATP for every 1 glucose

◦ occurs in cytosol why does that make evolutionary sense?

Glycolysis

Life on Earth first evolved without free 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 organisms still utilize

glycolysis

Evolutionary perspective

10 reactions◦ convert

6C glucose to two 3C pyruvate

◦ produce 2 ATP & 2 NADH

Overview

glucoseC-C-C-C-C-C

fructose-6PP-C-C-C-C-C-C-P

DHAPP-C-C-C

G3P (PGAL)

C-C-C-P

pyruvateC-C-C

2 ATP2 ADP

2 NAD+

2 NADH4 ADP4 ATP

activationenergy

G3P = glyceraldehyde-3-phosphateDHAP = dihydroxyacetone phosphate

2 PiTHE ELECTRON CARRIERNAD+ IS A COENZYME

Glycolysis summary endergonicinvest some ATP

exergonicharvest a little ATP & a little NADH

yield2 ATP2 NADH

Glucose “priming”◦ get glucose ready

to split phosphorylate

glucose rearrangement

◦ split destabilized glucose

1st half of glycolysis (5 reactions)

PGAL

Energy Harvest◦ NADH production

G3P donates H oxidize sugar reduce NAD+

NAD+ NADH◦ ATP production

G3P pyruvate sugars donate P ADP ATP

2nd half of glycolysis (5 reactions)

ATP

Net gain = 2 ATP◦ some energy investment (-2 ATP)◦ small energy return (+4 ATP)

1 6C sugar 2 3C sugars

Energy accounting of glycolysis

2 ATP 2 ADP

4 ADP 4 ATP

glucose pyruvate2x6C 3C

Not a lot of energy…◦ for 1 billon years+ this is how life on Earth

survived… Why? slow growth, slow reproduction only harvest 3.5% of energy stored in glucose

more carbons to strip off = more energy to harvest

Is that all there is?

O2

O2

O2

O2

O2

glucose pyruvate6C 2x 3C

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

Glycolysis

Going to run out of NAD+

◦ without regenerating NAD+, energy production would stop

◦ another molecule must accept H from NADH

We can’t stop there….

NADHHow is NADH recycled to NAD+?

Another molecule must accept H from NADH◦ aerobic respiration

to Electron Transport Chain in mitochondria ◦ anaerobic respiration

ethanol fermentation lactic acid fermentation

How is NADH recycled to NAD+?

O2

O2

NADH

which path you use depends on who you are…

which path you use depends on who you are…

Bacteria, yeast

Fermentation (anaerobic)

1C3C 2Cpyruvate ethanol + CO2

Animals, some fungi

pyruvate lactic acid3C 3C

beer, wine, bread

cheese, anaerobic exercise (no O2)

NADH NAD+

NADH NAD+

to glycolysis

to glycolysis

Alcohol Fermentation

1C3C 2Cpyruvate ethanol + CO2

NADH NAD+

Dead end process at ~12%

ethanol, kills yeast

can’t reverse the reaction

bacteria yeast

Reversible process once O2 is

available, lactate is converted to pyruvate by liver

Lactic Acid Fermentationpyruvate lactic acid

3C 3CNADH NAD+

O2

animals

Pyruvate

Pyruvate is a branching point

O2O2

Kreb’s cyclemitochondria

fermentation

The Point is to Make ATP!

2006-2007

ATP

What’s the point?

H+

ADP + Pi

H+H+

H+

H+ H+

H+H+H+

Set up a H+

gradient Allow the H+

to flow through ATP synthase

ADP + Pi ATP

And how do

we do that?

ATP

Have we done that yet?