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??