1. Cellular Respiration

2. Photosynthesis uses energy from sunlight to transform carbon dioxide and water into sugar (glucose) and water.
Organisms can use the chemical energy stored in the glucose by converting the chemical energy into a useable form.
Cellular respiration is the process where glucose is broken down and the energy is used to make ATP.
ATP is the main energy-storing molecule used by living organisms.
Cellular respiration can be broken down into 3 stages.

3. 1. Glycolysis:
Glycolysis takes place in the cytoplasm of most prokaryotic and all eukaryotic cells.
Glycolysis involves the breaking down of glucose to release the energy held with the chemical bonds.
The product of glycolysis is Pyruvic acid.

4. How does glycolysis break apart glucose?
Through a series of reactions catalyzed by enzymes (makes the reaction go faster) that change glucose one step at a time.
4 ATP molecules are synthesised, but 2 molecules of ATP were needed to start the process, therefore the net gain is 2 ATP molecules.

5. Overall Equation: C6H12O6 + 6 O2  6 CO2 + 6 H2O
After glycolysis there are 2 paths to take depending on the presence or absence of oxygen.

6. If oxygen present = RESPIRATION
This is an aerobic process, which means it requires oxygen.
It takes pyruvic acid molecules from glycolysis and oxygen to release ATP

7. 2. The Krebs Cycle Does not produce a final end product.
Takes place in the mitochondria of the cell
Is a cycle of continuous reactions
9 reactions and 9 intermediate molecules
CO2 is released from the cell at two places
At 4 places in the cycle, a pair of high-energy electrons are accepted by electron carriers.

8. Let’s sum up the Krebs Cycle
2 C atoms added (from the breakdown of pyruvic acid)
2 C atoms removed (in 2 molecules of CO2)
3 molecules of NAD+ converted to NADH
1 molecule of FAD converted to FADH2
1 molecule of GFP converted to GTP

9. The carbon atoms from the glucose end up as CO2 and the CO2 is a waste product that is released to the cell.
So what happens to the molecules of NADH and FADH2? And what about oxygen?

10. 3. Electron Transport Chain
Occurs in the inner membrane of the mitochondria.
The chain is a series of transport enzymes that passes high-energy electrons from NADH and FADH2 through a series of reactions.
At the end, the high-energy electrons combine with H+ (from the fluid inside the cell) and O2 to form H2O
Oxygen is needed as the final electron acceptor.

11. YIELD:
10 NADH converts to 30 ATP
2 FADH2 converts to 4 ATP (FADH produces 2 ATP & NADH produces 3 ATP)

12. If oxygen NOT present: ANAEROBIC RESPIRATION
When O2 is NOT present, the respiratory chain shuts down and therefore only glycolysis works.
Occurs in the cytoplasm
In animals:
Pyruvic acid is converted to lactic acid
Lactic acid is toxic to cells and causes cramps, fatigue and even death.

13. In plants and yeast cells:
Pyruvic acid leads to alcohol and CO2

14. Only 2 ATP molecules are produced per glucose molecule and therefore very inefficient.
If O2 is re-introduced the lactic acid converts back to pyruvic acid and aerobic respiration resumes.

15. Comparing ATP formation for Aerobic and Anaerobic respiration: