REDOX reactions in respiration

Equations for aerobic respirationAll of these are fine!....

Equation for Cellular Respiration

6CO2 + 6H20 + e- + 36-38ATP

+ heat

C6H12O6 + 6O2

YIELDS

What are REDOX reactions in respiration?

• ‘REDOX’ means ‘oxidation and reduction’• You can’t have one without the other• REDOX reactions involve ELECTRON TRANSFER• Organic molecules contain lots of energy locked in

their covalent bonds• Redox reactions TRANSFER this bond energy in the

form of ELECTRONS to ELECTRON CARRIERS which can temporarily store it and move it to ultimately synthesise ATP

Energy metabolism and REDOX reactions

• REDOX (oxidation-reduction) reactions play a key role in energy flow through organisms

• This is because the electrons flowing from one molecule to another are carrying energy with them

REDOX reactionsOXIDATION REDUCTION

Loss of electrons Gain of electrons

Gain of oxygen Loss of oxygen

Loss of hydrogen Gain of hydrogen

Results in C-O bonds Results in C-H bonds

Results in a compound with lower potential energy

Results in a compound with higher potential energy

OIL RIGLEO says GER

REDOX reactions in respirationCells tap energy from electrons transferred from organic fuels to oxygen

Glucose gives up energy as it is oxidized: it transfers its electrons (and energy) to water

The protons follow the electrons to produce water

Loss of hydrogen atoms

Energy

Gain of hydrogen atoms

Enzymes remove electrons from glucose molecules and transfer them to a coenzyme

Hydrogen carriers such as NAD+ and FED shuttle electrons in redox reactions

OXIDATION

Dehydrogenaseand NAD+

REDUCTION

• NADH delivers electrons to a series of electron carriers in an electron transport chain

• As electrons move from carrier to carrier, their energy is released in small quantities

Redox reactions release energy when electrons “fall” from a hydrogen carrier to oxygen

Energy released and now

available for making ATP

ELECTRON CARRIERS

of the electron transport chain

Electron flow

Glycolysis: Always the initial stage of respiration

• Location: cytoplasm• Substrate: glucose• Requires input of 2 ATP• Products: pyruvate,

(NADH), 4 ATP Glycolysis is an anaerobic process: no oxygen required

the movie...

Summary of glycolysis

1. Occurs in the cytoplasm of the cell2. Two ATP molecules are used to start the process

(‘energy investment phase’)3. A total of 4 ATP’s are produced (net gain of 2 ATP)4. 2 molecules of NADH are produced5. Involves substrate level phosphorylation, lysis, oxidation

and ATP formation6. Controlled by enzymes: when ATP levels in the cell are

high, feedback inhibition will block the first enzyme in the pathway

7. Produces 2 pyruvate molecules at the end