Warm Up 11/1

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

2. Explain photophosphorylation in terms of chemiosmosis.

Photophosphorylation is the production of ATP using the energy of sunlight and is possible because 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 synthesize ATP from ADP and phosphate.

3. State the final products of the two photosystems involved in the light-dependent reactions of photosynthesis.

ATP and NADPH

4. How are the products of the light-dependent reaction important to the light-independent reaction?

ATP and NADPH are oxidized to provide the energy to reduce glycerate-3-phosphate into triose phosphate.  Without ATP and NADPH, the light-independent reaction will not occur.