Cellular RespirationChapter 7

Cellular RespirationCells convert

carbon from glucose molecules into carbon dioxide and release energy

C6H12O6 + 6 O2 6 CO2 + 6 H2O + energy

Cellular RespirationEnergy released used to make ATP, main

energy source for cell processes

Primary fuel for respiration is glucose

GlycolysisOccurs in cytoplasm

Step 1: Phosphates from 2 ATP attach to a molecule of glucose

Step 2: These phosphates destabilize the molecule and it splits into 2 molecules of G3P

Glycolysis

Step 3: After another phosphate is added, G3P “reduces” NAD+ to NADH by adding electrons to it

GlycolysisStep 4: 2

phosphates from each molecule are used to convert 2 ADPs into 2 ATPs

Result is two 3-carbon molecules called “pyruvic acid” or “pyruvate”

TerminologyReactions that require oxygen to

take place = aerobic

Reactions that do not require oxygen = anaerobic

Aerobic Respiration

Krebs CycleBefore Krebs Cycle:

Pyruvate releases 1 carbon in the form of CO2 to become a compound known as Acetyl-CoA (makes an NADH)

Step 1: This 2-carbon molecule is then added to oxaloacetic acid to create a 6-carbon molecule

Krebs CycleStep 2: 2 CO2 molecules

released and 2 NADH molecules created in succession

This results in a 4-carbon molecule

4-carbon is recycled into oxaloacetic acid, creating ATP, NADH, and FADH2

Electron TransportNADH and FADH2

donate electrons to enzymes along inner mitochondrial membrane

Energy from electrons used in electron transport chain to pump H+ ions out of mitochondrial matrix• Concentration gradient created

ChemiosmosisAs in

photosynthesis, energy from the diffusion of H+ used to make ATP from ADP

Leftover (used-up) electrons and H+ that has diffused into mitochondria combine with O2 to create H2O, which is released

Electron Transport

Even though some ATP is produced earlier, most is produced here

Without oxygen present, electron transport chain and Krebs cycle stop

Efficiency of RespirationActual number of

ATP created from each glucose varies

Active transport of NADH consumes about 5% of energy

Glycolysis without the other steps results in 2 ATP instead of 38!

Anaerobic Respiration

FermentationRecycles NADH so glycolysis (ATP

production) can continue

Lactic Acid FermentationOccurs in eukaryotes,

specifically humans & animals

Pyruvate can accept electrons from NADH and is converted to lactic acid

Lactic acid buildup causes muscle fatigue

Alcoholic FermentationOccurs in plants, fungi

(yeast), prokaryotes

CO2 released, converting pyruvate to a 2-carbon molecule

Electrons added from NADH to convert 2-carbon molecule to ethanol

Alcoholic FermentationUsed to produce

alcoholic beverages and “biofuel” (ethanol)

Used to make bread rise (CO2)

A REVIEW

PhotosynthesisCO2 + H2O + light energy glucose + O2

Autotrophs ONLY!

Occurs in chloroplasts

Respirationglucose + O2 CO2 + H2O + energy

BOTH atuotrophs and heterotrophs

(ATP-heavy part) occurs in mitochondria