Clicker Question #1

Clicker Question #11. 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

GlycolysisGlucose

2Pyruvic

acid

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 oxidationThe 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