Biology Diagram about Photosynthesis

Summary:

Photosynthesis, the process by which plants convert sunlight into energy, involves two main stages: light-dependent and light-independent. In the light-dependent stage, chlorophyll, a pigment found in the chloroplasts of plant cells, plays a crucial role. It absorbs light energy and initiates a series of reactions that generate ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate), essential for the light-independent stage.

During the light-dependent stage, chlorophyll captures the energy from sunlight. This energy splits water molecules into hydrogen ions (H+) and electrons (e^-). This process, known as photolysis, releases oxygen as a byproduct. The hydrogen ions and electrons are then used to generate ATP through chemiosmosis. Chemiosmosis occurs in the thylakoid membrane of the chloroplast, where protons are actively transported across the membrane and create a proton gradient. The movement of protons back across the membrane through ATP synthase generates ATP, the energy currency of the cell.

The light-independent stage, also known as the Calvin cycle, takes place in the stroma of the chloroplast. This stage does not directly rely on light, but it requires the products of the light-dependent stage—ATP and NADPH. The Calvin cycle primarily aims to convert carbon dioxide (CO2) into glucose. The process begins with the fixation of CO2 by the enzyme ribulose bisphosphate carboxylase/oxygenase (Rubisco). This enzyme combines CO2 with a five-carbon sugar called ribulose bisphosphate (RuBP) to form an unstable six-carbon molecule. This molecule quickly breaks down into two three-carbon molecules known as 3-phosphoglycerate (PGA).

The PGA molecules are then converted into glyceraldehyde 3-phosphate (G3P), a three-carbon sugar. Some G3P molecules are used to regenerate RuBP, while others produce glucose and other organic molecules needed for plant growth and metabolism. The energy required for these reactions comes from the ATP and NADPH generated in the light-dependent stage. NADPH supplies the necessary electrons, while ATP provides the energy for the synthesis of glucose.

Excerpt:

Biology Diagram about Photosynthesis

Light – Dependent and light – Independent
Stages of Photosynthesis
Carbon dioxide + water light, glucose + oxygen
6C02 + 6H20 light, C6Hi20s +602