Chapter 5.2 Photosynthesis

Here’s a detailed summary of Lecture Seven - Photosynthesis:

1. Photosynthesis and Cellular Respiration are Complementary

• Photosynthesis: Converts light energy into chemical energy (glucose) in plants, algae, and some bacteria.

• Cellular Respiration: Breaks down glucose to release energy (ATP) in all living organisms.

• Interdependence: The oxygen produced in photosynthesis is used in respiration, while the carbon dioxide released in respiration is used in photosynthesis.

2. Light-Dependent Reactions: Producing ATP and NADPH

• Occurs in the thylakoid membranes of chloroplasts.

• Uses sunlight to split water molecules (photolysis), releasing oxygen (O₂).

• Produces ATP and NADPH, which are energy carriers needed for the next stage.

3. The Calvin Cycle (Light-Independent or Dark Reactions)

• Occurs in the stroma of the chloroplast.

• Uses ATP and NADPH from the light reactions to fix carbon dioxide (CO₂) into organic molecules.

• RuBisCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase) is the enzyme that catalyzes carbon fixation, making it one of the most important (and energetically expensive) enzymes in life.

4. Carbon, Oxygen, and Water Recycling in Life

• Carbon Cycle: Plants take in CO₂, convert it into glucose, and release oxygen.

• Water Cycle: Water is split in photosynthesis and reformed in respiration.

• Oxygen Cycle: Oxygen is produced in photosynthesis and consumed in respiration.

This lecture highlights the interconnection of energy cycles in nature, emphasizing how photosynthesis and respiration sustain life. Let me know if you need a deeper explanation on any topic!