Warm-Up 11/4

1. Draw and label a diagram showing the structure of a chloroplast as seen in electron micrograph a

2. Photophosphorylation is the production of ATP using the energy of sunlight. Photophosphorylation is made possible as a result of chemiosmosis. Chemiosmosis is the movement of ions across a selectively permeable membrane, down their concentration gradient. During photosynthesis, light is absorbed by chlorophyll molecules. Electrons within these molecules are then raised to a higher energy state. These electrons then travel through Photosystem II, a chain of electron carriers and Photosystem I. As the electrons travel through the chain of electron carriers, they release energy. This energy is used to pump hydrogen ions across the thylakoid membrane and into the space within the thylakoid. A concentration gradient of hydrogen ions forms within this space. These then move back across the thylakoid membrane, down their concentration gradient through ATP synthase. ATP synthase uses the energy released from the movement of hydrogen ions down their concentration gradient to synthesise ATP from ADP and inorganic phosphate.

3. ATP and NADPH

4. NADPH is generated in the light-dependent reactions as a powerful reducing agent. In the Calvin cycle, it is responsible for the reduction of 1,3-bisphosphoglycerate (1,3-BPG) into glyceraldehyde-3-phosphate. ATP energy is used to run the cycle.