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Clicker Question #1
1. What compound directly provides energy for cellular work?
A. DNA B. C6H12O6 C. glucose D. ATP E. fat
Energy ConversionFuel rich inchemicalenergy
Energy conversionWaste productspoor in chemical
energy
Gasoline
Oxygen
Carbon dioxide
WaterEnergy conversion in a car
Energy for cellular work
Energy conversion in a cell
Heatenergy
Heatenergy
Carbon dioxide
Water
Food
Oxygen
Combustion
Cellularrespiration
Kinetic energy
of movement
ATP
Cellular RespirationCellular respiration: A catabolic energy yielding pathway in which oxygen and organic fuels are consumed and ATP is produced
• An aerobic process—it requires oxygen
Organic + Oxygen Carbon + Water + EnergyCompounds
Dioxide
Summary equations:
Cellular Respiration
C6H12O6 CO2O2 H2O
Glucose Oxygen Carbondioxide
Water
6 66
Reduction
Oxidation
Oxygen gains electrons (and hydrogens)
Glucose loses electrons(and hydrogens)
•By oxidizing glucose, energy is taken out of “storage” and made available for ATP synthesis
3 metabolic stages:
*glycolysis *Krebs cycle
*electron transport chain and oxidative phosphorylation
*Substrate-level phosphorylation
*Oxidative phosphorylation
Cellular Respiration
Cytoplasm
Cytoplasm
Animal cell Plant cell
Mitochondrion
High-energyelectronscarriedby NADH
High-energyelectrons carriedmainly byNADH
CitricAcidCycle
ElectronTransport
Glycolysis
Glucose2
Pyruvicacid
ATP ATP ATP
Figure 6.6
CytoplasmCytoplasm
Cytoplasm
Animal cell Plant cell
Mitochondrion
Mitochondrion
High-energyelectronscarried
by NADH
High-energyelectrons carried
mainly byNADH
CitricAcidCycle
ElectronTransport
Glycolysis
ATP ATP ATP2 2 ~34~38 ATP per
glucose
Metabolic Disequilibrium
*Multi-step open system
Glycolysis harvests chemical energy by oxidizing glucose to pyruvate
Glycolysis: Energy Investment Phase
1) Glucose is phosphorylated
2) G-6-P is rearranged
3) Addition of another phosphate group
5) Conversion b/w the 2 3-carbon sugars
4) Cleavage into 2 3-carbon sugars
6) Two components: *electron transfer *Phosphate group addition
Glycolysis: Energy Payoff Phase
7) ATP production
8) Rearrangement of phosphate group
9) Loss of water
10) ATP production
Fermentation enables cell to produce ATP w/o O2
aerobicanaerobic
*Fermentation generates ATP by substrate-level phosphorylation
aerobicanaerobic
The presence or absence of O2 dictates the fate of pyruvate
The Krebs cycle: energy-yielding oxidation
The junction b/w glycolysis and the Krebs cycle:
Multienzyme complex:
1) Removal of CO2 2) Electron transfer *pyruvate dehydrogenase 3) Addition of CoA
The Krebs cycle: energy-yielding oxidation
1) Addition of 2 Carbons Citrate
synthase 2)
Isomerization Aconitase
3) *Loss of CO2 *electron transfer
Isocitrate dehydrogenase
4) *Loss of CO2 *electron
transfer a-ketoglutarate
dehydrogenase5) substrate-level
phosphorylation Succinyl CoA-synthetase
6) electron transfer Succinate
dehydrogenase
7) Rearrangement
of bonds Fumarase
8) electron transfer Malate dehydrogenase
Electron transport and ATP synthesis
*Multi-step open system
Generation and maintenance of an H+ gradient*Exergonic flow of e-, pumps H+ across the membrane*chemiosmosis
high energy electrons
*How does the mitochondrion couple electron transport and ATP synthesis?
ATP synthase
Versatility of Cellular Respiration
Food
Polysaccharides Fats Proteins
SugarsGlycerol Fatty acids
Amino acids
Glycolysis AcetylCoA
CitricAcidCycle
ElectronTransport
ATP
– In addition to glucose, cellular respiration can “burn”:• Diverse types of carbohydrates• Fats• Proteins