Photosynthesis, respiration, and metabolism are fundamental processes in plants that are essential for their survival and growth.
Photosynthesis is the process by which plants use light energy, carbon dioxide, and water to produce glucose (a type of sugar) and oxygen. The process takes place in the chloroplasts of plant cells, and it involves two main stages: the light-dependent reactions and the light-independent reactions (also known as the Calvin cycle). During the light-dependent reactions, light energy is used to produce ATP and NADPH, which are then used in the light-independent reactions to convert carbon dioxide into glucose.
Respiration, on the other hand, is the process by which plants (and all living organisms) break down glucose to produce ATP, the energy currency of cells. Respiration takes place in the mitochondria of plant cells, and it involves three main stages: glycolysis, the citric acid cycle, and oxidative phosphorylation. During glycolysis, glucose is broken down into pyruvate, which is then used in the citric acid cycle to produce ATP and other molecules. Finally, oxidative phosphorylation uses the energy released from these processes to produce even more ATP.
Metabolism refers to the overall set of chemical reactions that occur in plants. It includes both photosynthesis and respiration, as well as other processes such as the synthesis of new molecules (such as proteins and lipids) and the breakdown of old or damaged molecules for recycling. Metabolism also includes the storage and use of energy reserves such as starch and oils.
Together, these processes allow plants to produce the energy and nutrients they need to survive and grow, and to interact with their environment in complex ways.