Photosynthesis Overview

Overview of Photosynthesis

• Definition: 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.
• Importance: Produces oxygen and organic compounds necessary for life on Earth.

Light-Dependent Reactions

• Occur in thylakoid membranes of chloroplasts.
• Light energy is absorbed by pigments such as chlorophyll and converted into ATP and NADPH.
• Two stages:
  1. Light absorption: Light energy is absorbed by pigments, exciting electrons.
  2. Electron transport: Electrons are passed through a series of electron carriers, generating ATP and NADPH.

Light-Independent Reactions (Calvin Cycle)

• Occur in stroma of chloroplasts.
• Use ATP and NADPH produced in light-dependent reactions to convert CO2 into glucose.
• Three stages:
  1. Carbon fixation: CO2 is fixed into a 3-carbon molecule called 3-phosphoglycerate (3-PGA).
  2. Reduction: 3-PGA is reduced to form glyceraldehyde 3-phosphate (G3P).
  3. Regeneration: G3P is used to regenerate RuBP, the 5-carbon molecule necessary for carbon fixation.

Inputs and Outputs

• Inputs:
  • Light energy
  • CO2
  • H2O
• Outputs:
  • Glucose (C6H12O6)
  • O2

Factors Affecting Photosynthesis

• Light intensity: Increased light intensity can increase photosynthesis rate.
• Temperature: Optimal temperature range for photosynthesis varies among plants, but generally between 20-30°C.
• Water availability: Drought can limit photosynthesis.
• CO2 concentration: Increased CO2 concentration can increase photosynthesis rate.

Types of Photosynthesis

• Oxygenic photosynthesis: Produces oxygen as a byproduct, characteristic of plants, algae, and cyanobacteria.
• Anoxygenic photosynthesis: Does not produce oxygen, characteristic of some bacteria.

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.
• It produces oxygen and organic compounds necessary for life on Earth.

Light-Dependent Reactions

• Light-dependent reactions occur in thylakoid membranes of chloroplasts.
• They involve the absorption of light energy by pigments such as chlorophyll and its conversion into ATP and NADPH.
• These reactions consist of two stages: light absorption and electron transport.

Light-Independent Reactions (Calvin Cycle)

• Light-independent reactions occur in the stroma of chloroplasts.
• They use ATP and NADPH produced in light-dependent reactions to convert CO2 into glucose.
• These reactions consist of three stages: carbon fixation, reduction, and regeneration.

Inputs and Outputs

• The inputs for photosynthesis are light energy, CO2, and H2O.
• The outputs are glucose (C6H12O6) and O2.

Factors Affecting Photosynthesis

• Light intensity: Higher light intensity can increase the rate of photosynthesis.
• Temperature: The optimal temperature range for photosynthesis varies among plants, but is generally between 20-30°C.
• Water availability: Drought can limit photosynthesis.
• CO2 concentration: Higher CO2 concentration can increase the rate of photosynthesis.

Types of Photosynthesis

• Oxygenic photosynthesis: Produces oxygen as a byproduct, characteristic of plants, algae, and cyanobacteria.
• Anoxygenic photosynthesis: Does not produce oxygen, characteristic of some bacteria.