Photosynthesis Overview

Overview of Photosynthesis

• Photosynthesis is the process by which plants, algae, and some bacteria convert light energy from the sun into chemical energy in the form of organic compounds, such as glucose.
• This process occurs in specialized organelles called chloroplasts, which are present in plant cells.

Light-Dependent Reactions

• Light energy is absorbed by pigments such as chlorophyll and converted into ATP and NADPH.
• These reactions occur in the thylakoid membranes of the chloroplast and involve the following steps:
  1. Light absorption by pigments
  2. Excitation of electrons
  3. Transfer of electrons to electron acceptors
  4. Formation of ATP and NADPH

Light-Independent Reactions (Calvin Cycle)

• The energy from ATP and NADPH is used to convert CO2 into glucose.
• These reactions occur in the stroma of the chloroplast and involve the following steps:
  1. Carbon fixation (CO2 is fixed into a 3-carbon molecule)
  2. Reduction of 3-carbon molecules to form glyceraldehyde 3-phosphate (G3P)
  3. Regeneration of RuBP (the 5-carbon molecule that binds to CO2)
  4. Production of glucose from G3P

Importance of Photosynthesis

• Provides energy and organic compounds for plants to grow and develop
• Supports life on Earth by producing oxygen and food for heterotrophic organisms
• Plays a critical role in the Earth's carbon cycle and climate regulation

Factors Affecting Photosynthesis

• Light intensity and quality
• Temperature
• Water availability
• CO2 concentration
• pH and nutrient availability