1. THE PROCESS OF CELLULAR RESPIRATION
Section 5.3

2. C6H12O6(s) + 6 O2(g) → 6 CO2(g) + 6 H2O(l) + energy
Cellular respiration is used to release the energy stored in glucose (released in the form of ATP)

3. THREE WAYS TO RELEASE ENERGY
1. Aerobic Cellular Respiration
Needs oxygen to produce ATP
i.e. humans, mammals, plants, some fungi, and bacteria
2. Anaerobic Cellular Respiration
Does not require oxygen to produce ATP
i.e. some bacteria, deep ocean dwellers
3. Fermentation
An anaerobic process
i.e. yeasts, occurs in muscle cells of mammals

4. AEROBIC CELLULAR RESPIRATION
An oxidation reaction that breaks down glucose to make energy
Involves four stages:
Glycolysis – occurs in the cytoplasm of a cell
Pyruvate oxidation – occurs in the mitochondria
Kreb’s cycle – occurs in the mitochondria
Electron transport and chemiosmosis – occur in the inner mitochondrial membrane

6. GLYCOLYSIS IS AN ANAEROBIC PROCESS
Process that splits the glucose molecule in half making 2 three-carbon molecules
These are called pyruvate molecules
Uses ATP to start this process but ATP is also made in this process
Also reduces NAD+ through the process to produce NADH

7. PYRUVATE OXIDATION
A process in which pyruvate loses a carbon atom in the form of CO2
The remainder of pyruvate bonds to a molecule known as Coenzyme A (CoA)
Another NAD+ molecule is reduced to NADH
The new molecule is known as Acetyl CoA and this 2-carbon molecule moves to the Kreb’s cycle

8. KREB’S CYCLE Figure 5.19, page 187
Acetyl-CoA enters the Krebs cycle and goes through reactions to become a 6-carbon molecule
Produces CO2 as a by product
Reduces molecules of NAD+ and FAD to produce NADH and FADH2
Two ATP molecules are generated

10. ELECTRON TRANSPORT Most of the ATP is made here
Electron transport chain is similar to the one in chloroplasts
Electrons released by NADH and FADH2
As the electrons pass along this chain they release energy
This energy pumps hydrogen ions from the matrix to the intermembrane space
These ions can only exit through ATP synthase complexes (chemiosmosis)
Produces 36 molecules of ATP

12. WHY IS OXYGEN IMPORTANT?
Oxygen is very important in aerobic cellular respiration
Oxygen is the final electron acceptor
It takes the electron from the ETC and combines with hydrogen ions to make water
If oxygen was not there this process would stop as the electrons could not go anywhere

13. ANAEROBIC CELLULAR RESPIRATION
Is used when there is no oxygen available
Is not as efficient as aerobic cellular respiration
Provides much less ATP
The final electron acceptor in anaerobic cellular respiration is usually an inorganic molecule
i.e. sulfate, nitrate or carbon dioxide
Is not useful for long term

14. Occurs in the cytoplasm of a cell
Includes two stages:
Glycolysis
Fermentation – can use 2 different pathways: lactate fermentation or ethanol fermentation
Glycolysis we have discussed earlier

15. LACTATE FERMENTATION
Used when cells are temporarily without oxygen i.e. during strenuous exercise because muscles are using so much energy
Used NADH to convert pyruvate to lactate (lactic acid)
the NAD+ that was created is recycled (made into NADH again) to continue the process
If too much lactic acid builds up in the muscles fatigue and cramp

16. ETHANOL FERMENTATION
Occurs in yeast cells and is used in wine, beer and bread making
Convert pyruvate to ethanol and carbon dioxide
Gives off carbon dioxide as waste
NADH molecules are oxidized to make NAD+ during this process
Ethanol is also released as a waste product