Photosynthesis: An Overview

1. Photosynthesis: An Overview

2. Warm up 11/12 • Define these words • Pigment • Chlorophyll • Thylakoid • Stroma • Light dependent reactions • Light independent reaction

3. Learning Objectives • Explain the role of light and pigments in photosynthesis. • Explain the role of electron carrier molecules in photosynthesis. • State the overall equation for photosynthesis.

4. Light Light energy from the sun must be captured for photosynthesis to occur. Sunlight is “white” light—actually a mixture of different wavelengths. (ROY-G-BIV)

5. Pigments Pigments – plants gather the suns energy with light absorbing molecules called pigment What role do pigments play in the process of photosynthesis? Photosynthetic organisms capture energy from sunlight with pigments

6. Chlorophyll Photosynthetic organisms capture energy from sunlight with pigments—principally with chlorophyll.

7. Chlorophyll – green pigments 2 main types of chlorophyll Chlorophyll a and Chlorophyll b • Absorbs light very well in the blue-violet spectrum and red regions of visible spectrum Chlorophyll a – found in all plants, algae, and cyanobacteria Chlorophyll b – found in all plants, and green algae

8. Chlorophyll Photosynthesis takes place inside organelles called chloroplasts. Plant Cell Chloroplast

9. Chloroplast Chloroplasts contain Thylakoids- saclike photosynthetic membranes • Chlorophyll is located in thylakoid membrane • Grana – thylakoids are interconnected and arranged in stacks known as grana Stroma – fluid portion of the chloroplast, outside of the thylakoids

10. Chloroplast In plants, photosynthesis takes place inside chloroplasts. Stroma Thylakoid Granum Thylakoid membrane

11. Chloroplasts and light transmission • What is so special about chlorophyll that makes it so important for photosynthesis? • light is a form of energy, any compound that absorbs light absorbs energy

12. High Energy Electrons The high-energy electrons produced by chlorophyll are highly reactive and require a special “carrier.”

13. High Energy Electrons An electron carrier is a compound that can accept a pair of high-energy electrons and transfer them, along with most of their energy, to another molecule. NADP+ accepts and holds 2 high energy electrons, along with a hydrogen ion (H+) NADP+  NADPH This is one way in which energy from sunlight can be trapped in chemical form.

14. High Energy Electrons NADPH can carry the high-energy electrons that were produced by light absorption in chlorophyll to chemical reactions elsewhere in the cell.

15. An Overview of Photosynthesis Photosynthesis uses the energy of sunlight to convert water and carbon dioxide (low-energy reactants) into high-energy sugars and oxygen (products). Carbon dioxide + Water →Sugars + Oxygen light 6CO2 6H2O C6H12O6 6O2 light + → +

16. Photosynthesis and Light Photosynthesis involves two sets of reactions: Light-dependent reactions Light-independent reactions

17. Light-Dependent Reactions Light-dependent reactions require the direct involvement of light and light-absorbing pigments. • Uses energy from sunlight to produce energy rich compounds like ATP • Takes place in the Thylakoid • Input: Water • Output: Oxygen (O2) Water Oxygen

18. Light-Independent Reactions Light-independent reactions use ATP and NADPH molecules produced in the light-dependent reactions to produce high-energy sugars from carbon dioxide • No light is required • Take place outside the thylakoids, in the stroma • Input: CO2 • Output: sugar Carbon Dioxide Sugars andCarbohydrates

19. Interdependence of Reactions Light-dependent and light-independent reactions have an interdependent relationship. work together to capture the energy of sunlight and transform it into energy rich compounds like carbohydrates