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Chapter 6

IV. Glycolysis and AerobicRespiration

C6H12O6 + 6O2 6CO2 + 6H2O + Energy

Energy flowand chemicalrecycling in

theecosystem.

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Mitochondrion Structure

C6H12O6 + 6O2 6CO2 + 6H2O + Energy

Aerobic Respiration

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Overview

• Respiration – Extracting stored energyfrom glucose to form ATP.

• The breakdown of glucose occurs intwo stages.– Glycolysis (does not require oxygen)– Aerobic Respiration (Requires Oxygen)

• Preparatory step• Krebs Cycle (Citric Acid Cycle)• Electron Transport Chain

Energy Storing Compounds

• ADP + Pi ATP• NAD+ + 2e- + H+ NADH• FAD+ + 2e- + 2H+ FADH• Reduction = The addition of electrons.

– NAD+ + 2e- + H+ NADH• Oxidation = The removal of electrons

from a compound.– NADH NAD+ + 2e-

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Glycolysis

• Glycolysis – Glucose breaking downthrough the action of enzymes.

• Occurs in the cytoplasm of the cell.• Glycolysis does not require oxygen• Substrate-level phosphorylation =

The formation of ATP during glycolysisand the krebs cycle.

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Glycolysis - Summary

• 2ATP are used to “kick start” thereaction.

• 4 ADP are converted to 4 ATP viasubstrate level phosphorylation.

• 2 NAD+ are reduced to 2NADH.• 2 Pyruvate are produced

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Aerobic Respiration

• Occurs in themitochondrion.

• Three stages– Preparatory step– Krebs Cycle (Citric acid

cycle)– Electron Transport

Chain

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Aerobic Respiration – PreparatorySteps

• Pyruvate is converted to acetyl-CoA• NAD+ is reduced to NADH• CO2 is released.• Remember there are two pyruvate

molecules! So this reaction happens foreach pyruvate molecule!

Aerobic Respiration – Krebs Cycle(Citric acid cycle)

Named after Hans Kreb (1930s) The first compound created is citrate (citric

acid cycle) 3NAD+ are reduced to 3NADH. FAD+ is reduced to FADH2 1 ATP is created via substrate level

phosphorylation. 2CO2 are released. Remember that there are two acetyl-CoA!

This reaction occurs for each acetyl-CoA!

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Record Keeping – What wehave so far.

1 ATP x 2 = 2ATP1 FADH2 x 2 = 2 FADH2

3 NADH x 2 = 6NADHKrebs Cycle

1 NADH x 2 = 2NADHPreparatory steps

2 ATP (Net)2 NADHGlycolysis

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Aerobic Respiration - ElectronTransport Chain

• Occurs at the inner mitochondrial membrane.• This is the stage where most of the ATP is

made!• NADH and FADH2 are oxidized to NAD+ and

FAD+

• Electrons are released into the electrontransport chain.

• H+ is pumped into the intermembane spacecreating a concentration gradient.

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Aerobic Respiration - ElectronTransport Chain

• H+ passes back into the mitochondrialmatrix through ATP synthases whichgenerate ATP from ADP.

• Oxidative phosphorylation – Theformation of ATP as a result of theelectron transport chain.

Aerobic Respiration - ElectronTransport Chain

• Oxygen is the final electron acceptor!• Oxygen combines with 2H+ and two

electrons to form H2O!• Oxygen keeps the electrons moving

through the chain! Without oxygenthe electron transport chain wouldstop! No ATP would be generated!

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Other Sources of Energy

• Fats and Proteins can be used forenergy.

• A gram of fat provides twice as muchATP as a gram of glucose.

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