Bio 02/18 part 1

Introduction to Photosynthesis

• Definition: Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy stored in glucose.

Key Components of Photosynthesis

• Light Energy: Sunlight is the primary source of energy.

• Chlorophyll: A green pigment found in plant cells that absorbs sunlight, mainly in the blue and red wavelengths.

• Carbon Dioxide (CO₂): Taken in from the atmosphere through the leaf stomata.

• Water (H₂O): Absorbed through the roots from the soil.

Process of Photosynthesis

1. Light-dependent Reactions

• Occur in the thylakoid membranes of chloroplasts.

• Photolysis of Water: Water molecules split into oxygen, protons, and electrons under the influence of light.

• ATP and NADPH Production: Energy absorbed from light converts ADP to ATP and NADP+ to NADPH, which are energy carriers.

2. Light-independent Reactions (Calvin Cycle)

• Occur in the stroma of chloroplasts.

• Carbon Fixation: CO₂ is fixed into an organic molecule using ATP and NADPH from the light-dependent reactions.

• Produces glucose as the end product through a series of enzymatic reactions.

Importance of Photosynthesis

• Oxygen Production: Photosynthesis releases oxygen as a byproduct, essential for the survival of aerobic organisms.

• Food Source: Forms the basis of the food chain; plants are primary producers.

• Carbon Dioxide Reduction: Helps mitigate the greenhouse effect by absorbing CO₂ from the atmosphere.

Factors Affecting Photosynthesis

• Light Intensity: More light increases the rate of photosynthesis to a certain extent.

• Carbon Dioxide Concentration: Higher levels can boost the rate of photosynthesis up to a limit.

• Temperature: Enzymes involved in photosynthesis have optimal temperature ranges, affecting the reaction rate.

Conclusion

• Photosynthesis is vital not only for plants but for all life on Earth as it sustains food webs and regulates atmospheric gases.