Photosynthesis

Photosynthesis Process

Diagram Explanation:

• Light Reaction:

• Location: Thylakoid (inside the chloroplast).

• Inputs: Light and H2O (water).

• Outputs:

• Oxygen (O2) released into the air.

• ATP and NADPH (energy carriers) generated.

• Calvin Cycle:

• Location: Stroma (the free-floating fluid in the chloroplast).

• Inputs: CO2 (carbon dioxide).

• Outputs:

• Glucose, which is stored in roots for later use.

Glucose:

• Definition: The monomer (smallest unit) created by photosynthesis.

Polysaccharides from Glucose:

1. Starch:

• Structure: Composed of α-glucose monomers linked by 1–4 bonds.

• Function: Stored in plants as food to be used later for energy during cell respiration.

2. Cellulose:

• Structure: Made from β-glucose monomers linked by 1–4 bonds, with alternating orientations.

• Function: Used structurally in plants, such as in cell walls.

Photosynthesis

Equation:

6CO₂ + 6H₂O + Light → C₆H₁₂O₆ + 6O₂

Two Steps:

1. Light Dependent Reaction

2. Calvin Cycle

Carrier Molecules:

• ATP:

• Carries energy in bonds.

• Conversion: ADP → ATP.

• NADPH:

• Carries 2e⁻ and H⁺.

• Conversion: NADP⁺ → NADPH.

Light Dependent Reaction

• Occurs: Thylakoid.

• Reactants:

• H₂O.

• Light.

• Products:

• O₂.

• Carriers:

• Created and travel to the Calvin Cycle:

• ADP → ATP.

• NADP⁺ → NADPH.

Light Independent Reaction = Calvin Cycle

• Occurs: Stroma.

• Reactants: CO₂.

• Products: C₆H₁₂O₆ (Glucose).

• Carriers:

• Used to make glucose, break down, and travel back to the light reaction:

• ATP → ADP.

• NADPH → NADP⁺.

Cellulose Fibrils

• Diagram:

• Illustrates the structure of cellulose fibrils within a plant cell wall.

• Includes:

• Microfibril: Composed of cellulose.

• Hydrogen bonds: Hold the fibrils together.

• Plant cell: Cross-section showing the organization of cellulose in the cell wall.

What Affects the Rate of Photosynthesis?

1. Amount of Water or CO₂:

• A decrease in water or CO₂ decreases the rate of photosynthesis.

• Water shortage can slow or stop the process.

2. Temperature:

• Photosynthesis occurs within a temperature range of 0–35°C.

• Extremely low temperatures stop photosynthesis.

3. Light Intensity:

• An increase in light intensity increases the rate of photosynthesis.

Factors Affecting Photosynthesis (Graphs):

• Light Intensity: Rate of photosynthesis increases with higher light intensity until it plateaus.

• Carbon Dioxide Concentration: Higher CO₂ levels lead to an increased rate of photosynthesis until a certain point.

• Temperature: Rate peaks at an optimal temperature and then declines if the temperature is too high.