Photosynthesis and Respiration: The Energy Cycle
Photosynthesis is how plants make their own food using sunlight, water, and carbon dioxide. The equation is: 6H₂O + 6CO₂ → C₆H₁₂O₆ + 6O₂. This process is endothermic because it takes in light energy through chloroplasts.
Plants are clever with the glucose they make. They use it for respiration (releasing energy), convert it to starch for storage, make fats and oils, build cellulose for strong cell walls, and create amino acids for proteins. They even grab nitrate ions from soil to help with this!
Aerobic respiration is the opposite of photosynthesis - it breaks down glucose using oxygen to release energy. When oxygen runs out, cells switch to anaerobic respiration, which produces less energy but keeps things going.
Key Point: Respiration is exothermic (releases energy) while photosynthesis is endothermic (takes in energy) - they're perfect opposites!
Anaerobic respiration works differently depending on the organism. In animals, glucose becomes lactic acid. In plants and yeast, it produces ethanol and carbon dioxide - which is why we can make bread and alcoholic drinks through fermentation.