TYPES OF CELLULAR RESPIRATION
| Type of Cellular Respiration | Description | Oxygen Requirement | Key Steps/Processes | ATP Yield (per Glucose) |
|---|---|---|---|---|
| Aerobic Respiration | Most common and efficient form of respiration. | Requires Oxygen | 1. Glycolysis 2. Citric Acid Cycle (Krebs Cycle) 3. Electron Transport Chain | Up to 38 ATP |
| Anaerobic Respiration | Occurs in the absence of oxygen or in low-oxygen environments. | Oxygen Not Required | 1. Glycolysis 2. Fermentation (e.g., lactic acid or alcoholic fermentation) | Fewer than 38 ATP |
| Lactic Acid Fermentation | Anaerobic process in which pyruvate is converted to lactic acid. | No Oxygen Required | 1. Glycolysis 2. Lactic Acid Formation | 2 ATP (per glucose) |
| Alcoholic Fermentation | Anaerobic process in which pyruvate is converted to ethanol and CO2. | No Oxygen Required | 1. Glycolysis 2. Ethanol and CO2 Formation | 2 ATP (per glucose) |
NET GAIN OF ATP IN GLYCOLYSIS
| Glycolysis Step | Substrate/Reactants | Products | ATP Produced | ATP Consumed | Net ATP |
|---|---|---|---|---|---|
| Step 1: Phosphorylation | Glucose (1 molecule) | Glucose-6-phosphate (2 molecules) | 2 ATP (2 ATP used) | 0 ATP | 2 ATP |
| Step 2: Isomerization | Glucose-6-phosphate (2 molecules) | Fructose-6-phosphate (2 molecules) | 0 ATP | 0 ATP | 2 ATP |
| Step 3: Phosphorylation | Fructose-6-phosphate (2 molecules) | Fructose-1,6-bisphosphate (2 molecules) | 2 ATP (2 ATP used) | 0 ATP | 2 ATP |
| Step 4: Cleavage | Fructose-1,6-bisphosphate (2 molecules) | Dihydroxyacetone phosphate (2 molecules) and Glyceraldehyde-3-phosphate (2 molecules) | 0 ATP | 0 ATP | 2 ATP |
| Step 5: Isomerization | Dihydroxyacetone phosphate (2 molecules) | Glyceraldehyde-3-phosphate (2 molecules) | 0 ATP | 0 ATP | 0 ATP |
| Step 6: Oxidation and ATP Formation | Glyceraldehyde-3-phosphate (2 molecules) | 1,3-Bisphosphoglycerate (2 molecules) | 4 ATP (2 ATP produced, 2 ATP used) | 0 ATP | 4 ATP |
| Step 7: Phosphorylation | 1,3-Bisphosphoglycerate (2 molecules) | 3-Phosphoglycerate (2 molecules) | 0 ATP | 0 ATP | 4 ATP |
| Step 8: Isomerization | 3-Phosphoglycerate (2 molecules) | 2-Phosphoglycerate (2 molecules) | 0 ATP | 0 ATP | 4 ATP |
| Step 9: Dehydration | 2-Phosphoglycerate (2 molecules) | Phosphoenolpyruvate (2 molecules) | 0 ATP | 0 ATP | 4 ATP |
| Step 10: Phosphorylation | Phosphoenolpyruvate (2 molecules) | Pyruvate (2 molecules) | 4 ATP (2 ATP produced, 2 ATP used) | 0 ATP | 4 ATP |
| Net ATP Produced in Glycolysis | - | - | Total ATP Produced: 10 ATP | Total ATP Used: 4 ATP | Net ATP: 6 ATP |
Please note that glycolysis produces a total of 10 ATP molecules through substrate-level phosphorylation (direct ATP production) and consumes 4 ATP molecules (2 ATP used in Steps 1 and 3, and 2 ATP produced in Steps 6 and 10), resulting in a net gain of 6 ATP molecules per molecule of glucose metabolized during glycolysis.
