Energy is stored in the chemical bonds of glucose Light energy*  Chemical bond energy (ATP*) ATP* hydrolysis  ADP + Pi + energy* 6CO2 + 12H2O (H source) + energy*  glucose*

To synthesize organic molecules, it takes energy and reducing power. ATP Source of attachable H.

To retrieve energy from glucose: 1. strip away high energy electrons from the chemical bonds of glucose 2. this is oxidation (loss of electrons) 3. cellular respiration is a two-step process: remove electrons use the energy in those electrons

Glycolysis occurs in the cytoplasm of all living organisms enzymatic splitting of glucose yields 2 pyruvates net gain of 2 ATP and 2 NADH*

Substrate-level phosphorylation

Pyruvate oxidized (by NAD+) One C removed as CO2 Coenzyme A is added Leaves acetyl-CoA

Acetyl-CoA can have many fates: ATP synthesis (in mitochondria) fat synthesis lipid synthesis amino acid synthesis

2 CO2 3 NADH 1 FADH2 1 ATP original 4-C sugar

Electron Transport System

Photosynthesis vs. Cellular Respiration source of high-energy electrons used electrons cannot be recycled in mitochondria

Net results

ATP production decreases when ATP is plentiful.

Animal cells convert pyruvate to lactic acid in the absence of O2 Makes NAD+ available so glycolysis can continue

Yeast cells convert pyruvate to ethanol in the absence of O2