Cellular Respiration

Cellular Respiration: Harvesting Chemical Energy

• All living things need energy

• Energy in the form of…

•Food=chemical energy

• Cell

energy=ATP

C6H12O6 + 6O2→ 6H2O + 6CO2 + Energy

• Organic compounds store energy in their arrangement of atoms

• Fats, CH2O protein can all be used as fuel . Most commonly, cellular respiration is studied using glucose as the source.

• There are 2 energy-providing (catabolic) pathways– Cellular Respiration– Fermentation ( partial degradation of

sugar without oxygen)

Cells Recycle ATP

Four Stages of Cellular RespirationFour Stages of Cellular Respiration

• Glycolysis• Preparation for Citric Acid

Cycle• Citric Acid Cycle/Kreb’s Cycle• Electron Transport

• Respiration uses an electron chain to break the “fall” of electrons to several steps.

• Oxidation phosphorylation (adding a phosphate onto a compound in the presence of oxygen) accounts for 90% of the ATP generated by respiration.

GlycolysisGlycolysis

Splits a glucosemolecule into 2 - 3 Carbon molecules calledPYRUVATEPYRUVATE.

products: 2 ATP, NADH and pyruvate

What happens when there is no oxygenWhat happens when there is no oxygen to accept the electrons?to accept the electrons?

Only the process of glycolysis is carried out and lacticacid is produced in the muscles. The body cannottolerate much lactic acid and it must eventually be converted in the liver to pyruvate.

results in muscle soreness

AlcoholicAlcoholic FermentationFermentation

Some organisms carry out alcoholic fermentation. This wasdiscovered by Louis Pasteur in his study of the chemistryof wines. Yeasts break down the sugars in the juice topyruvate by glycolysis, then the pyruvate is dismantled toyeild CO2 and ETHANOL. If the fermentation continuesuntil all the sugar is used, a dry wine is produced. Iffermentation is stopped before all the sugar is used, thena sweet wine is produced.

Eukaryote vs Prokaryote Glycolytic pathways

Prokaryotes • Lack mitochondria??• Free enzymes break

down glucose-ATP

• 1 glucose=2 ATP• No O2 needed so…

•ANAEROBIC• Some,however…???

Quiz-anaerobic gylcolysis• Where in the cell does

gylcolysis occur?• Explain “it takes energy

to make energy”??• How much net ATP is

made?• What else is made?• 2 types of fermentation?

• Cytoplasm

• Invest 2 ATP get 4

• Net= 2 ATP

• CO2 + NADH

• Lactate or alcohol

The Fate of PYRUVATE

• Taken into mitochondria• Broken down to ACETATE

• CO2 produced

• Binds to large protein Coenzyme A to produce acetyl Coenzyme A

Back to Aerobic Respiration………….

Preparation for the Citric Acid CyclePreparation for the Citric Acid Cycle

The pyruvate looses acarbon leaving the 2 carbon molecule Acetyl CoA

CC

CO2

products: CO2, Acetyl CoA and NADH

The Citric Acid CycleThe Citric Acid Cycle

Products: CO2 ATP, NADH, FADH

The Citric Acid Cycle (TCA) or KREBS CYCLE

•CO2

•NADH & FADH

•2 more ATP

What is NADH?? FADH??• ENERGY CARRIER!• Same for FADH• Carrier to…?• … ETC

Quiz-Krebs cycle (TCA cycle)

• What are the reactants?• What is produced?

• What do we mean by nonmembrane reactions?

• What is NADH? FADH?• What is CoA and why is it

important?

• Pyruvate (C3)

• 2 ATP, CO2, NADH, FADH

• Enzymes not embedded

• Energy carriers• Escort molecule to

Krebs cycle

matrix

H+

H+

H+

H+ H+H+

outer membrane

inner membrane( ATP synthetase)

The matrix is a protein rich solution which contain theenzymes which run electron transport.

ATP SYNTHETASE is the enzyme which is responsible formaking ATP.

MitochondriaMitochondriaH+

H+NADH+

Mitochondria: Site of Electron Transport Chain

The Mitochondria have 2 layers/two membranes-• the outer membrane • inner membrane which has many

folds. • these folds are called Cristae

• The purpose of the cristae is to increase surface area, they hold the ATP synthase (which puts the ATP together• More ATP synthase more

ATP

The H+ which are brought to mitochondria accumulate between these two membranes.

The electrons are passedback and forth across themembrane where their energyis gradually decreased and usedto transport H+ through the membrane. Oxygen is the finalelectron acceptor and it joins withthe H+ to produce H2O.

If there is no oxygen, the electron chain cannot continuebecause there is no way to release electrons . .

electrons

Electron Transport Chain

Electron Transport Chain (ETC)

• Enzymes embedded in mitochondrial membrane– ATP Synthase

embedded in the inner mitochondrial wall. ATP Synthase synthesizes the ATP from the materials processed within the ETC

Products of the Electron Transport Chain

34 ATP

Water

+

glycolysis

NADH carries electrons to ETC

prepKrebs

Electron Transport chain

ATP

ONE GLUCOSE MOLECULE PRODUCES 34-36 ATP34-36 ATP

Glycolysis 4ATP

Krebs Cycle 2 ATP

•Glycolysis 4 ATP•Recycled -2 ATP

•Kreb’s Cycle 2 ATP•Electron Transport Chain 32-34 ATP

• 34-36 ATP

2 are recycled back to allow glycolysis to continue (-2)

ETC 2 ATP

Summary Quiz• What are the reactants of aerobic

respiration?? Products? Equation?• List the three respiratory stages:

– Where in the cell do each occur?– What are the products of each?

• Why is oxygen needed?• How much ATP is produced by

– Anaerobic gylcolysis?– Aerobic glycolysis?

• List the 2 types of fermentation??