Cellular Respiration and Glycolysis

Study Notes

Anaerobic process that occurs in the cytoplasm
Inputs: Glucose, 2 ATP
Outputs: 2 pyruvate, 4 ATP (2 net ATP), 2 NADH
There are two possible pathways following glycolysis:
- Aerobic Respiration: Occurs with oxygen, leading to Krebs Cycle and ETC
- Anaerobic Respiration: Occurs without oxygen, leading to either alcoholic or lactic acid fermentation

How does the fact that glycolysis occurs in the cytoplasm without oxygen provide clues about the early environment of Earth?
- Glycolysis is an ancient process, suggesting that early Earth likely had a low oxygen environment.
All organisms perform glycolysis. What does that say about the evolutionary timing of glycolysis compared to Krebs Cycle and ETC?
- Glycolysis is a universal process, indicating its evolution before the development of more complex processes like Krebs Cycle and ETC.

Krebs Cycle (Citric Acid Cycle)
- Happens in the mitochondrial matrix
- Converts pyruvate into Acetyl CoA, which powers the Krebs Cycle
- Inputs: Pyruvate
- Outputs: 11 NADH, 2 ATP, 2 FADH2, CO2
Electron Transport Chain (ETC)
- Happens in the inner membrane of the mitochondria
- NADH and FADH2 drop off their electrons at H+ pumps (cytochrome complex), becoming oxidized to NAD+ and FAD+
- Electrons pass through complexes, pumping H+ into the intermembrane space (chemiosmosis).
- Oxygen accepts the electrons to create H2O (oxygen gets reduced to H2O), and water leaves the cell.
- The H+ gradient forces H+ through ATP synthase, powering ATP synthase to phosphorylate ADP into ATP.
- Inputs: O2, NADH, FADH2
- Outputs: H2O, 32 ATP

How would the lack of oxygen affect the ETC and Krebs Cycle?
- Without oxygen, the ETC would stop, as oxygen is the final electron acceptor. This would also halt the Krebs Cycle, as it relies on NAD+ and FAD+ regeneration, which occurs in the ETC.
How does the Krebs Cycle serve as a link between glycolysis and the ETC?
- The Krebs Cycle produces NADH and FADH2, which are then used as electron carriers in the ETC.