4a. During photosynthesis and cellular respiration, energy is
transferred and transformed by different molecules and processes. In photosynthesis, energy from sunlight is absorbed by chlorophyll in plant cells and converted into chemical energy in the form of glucose. This process takes place in the chloroplasts of the plant cells.
On the other hand, cellular respiration is a metabolic process that occurs in the mitochondria of cells. During cellular respiration, glucose and oxygen react to produce carbon dioxide, water, and ATP (adenosine triphosphate), which is the primary energy currency of cells.
The energy transfer and transformation during these processes can be summarized as follows:
1. Photosynthesis:
- Sunlight energy is captured by chlorophyll molecules in the chloroplasts.
- This energy is used to convert water and carbon dioxide into glucose.
- Glucose molecules store chemical energy that is used by cells for various metabolic processes.
2. Cellular Respiration:
- Glucose is broken down in the presence of oxygen to release energy.
- This process occurs in multiple steps, including glycolysis, the Krebs cycle, and oxidative phosphorylation.
- During these steps, glucose is partially oxidized, releasing electrons, which are transferred to carrier molecules such as NADH and FADH2.
- The electrons from these carriers are then passed through the electron transport chain, releasing energy that is used to generate ATP.
- The final electron acceptor in the electron transport chain is oxygen, which combines with hydrogen ions to form water.
Overall, photosynthesis and cellular respiration are interconnected processes that involve the transfer and transformation of energy in living organisms. Photosynthesis converts light energy into chemical energy, while cellular respiration converts chemical energy stored in glucose into ATP, which can be used by cells for various functions.