1. PHOTOSYNTHESIS Chapter 8

2. Differentiate between Autotrophs and Heterotrophs Autotrophs Organisms that make their own food Plants, algae, and some bacteria Heterotrophs Organisms that obtain energy from foods that they consume Animals, fungi (mushrooms)

3. Energy Energy comes in many forms  light, heat, and electricity. Energy in most food originates from the sun. Energy molecules  chemical fuels used to power cellular activities

4. Energy ADP (adenosine diphosphate) - 2 phosphate groups Partially charged; when a cell has extra energy, it stores small amounts by adding a phosphate group to ADP to form ATP ATP (adenosine triphosphate) – 3 phosphate groups Fully charged; When a chemical bond is broken between phosphate 2 and 3, energy is released

5. Ways cells use ATP for energy Active transport Photosynthesis Cellular Respiration Protein synthesis Muscle contraction

6. However… ATP is NOT good for storing large amounts of energy. This is why we need glucose (food) which contains 90 times more energy. Cells can regenerate ATP from ADP by using energy released from a glucose molecule that has been broken down.

7. SECTION 2 Overview of Photosynthesis

8. Van Helmont Plants grow by taking material out of soil Mass of pot, soil, and seedling Watered 5 years Plant grew 75 kg; but, mass of pot (soil) did not change Concluded that mass of plant was gained from water because that was the only thing he had added to the pot.

9. Priestley Covered lit candle with jar and watched flame die out Hypothesized that something in air was necessary to keep candle burning…when used up, the flame would go out. Repeated with sprig of mint and observed that candle remained lit longer Concluded that the plant released oxygen.

10. Ingenhousz Used Priestly’s experiment; but, showed that this process only occurred when plant was exposed to light Both Priestly and Ingenhousz’s experiments showed that light was necessary for plants to produce oxygen.

11. What is photosynthesis? Plants use energy from sunlight to convert water and carbon dioxide into high energy carbohydrates (sugars and starches) and oxygen as a waste product. 6 CO 2 + 6 H 2 O + light  C 6 H 12 O 6 + 6 O 2

12. Light and Pigments How do plants capture energy from sunlight? Chloroplast contain a principal pigment (chlorophyll) which is used in photosynthesis What are pigments? Light absorbing molecules

13. 2 Main Types of Chlorophyll Chlorophyll a Absorbs light from red/orange regions of light spectrum Chlorophyll b Absorbs light from the blue-violet regions of light spectrum This is why green plants look green. Green light is reflected, not absorbed.

14. What happens when light is absorbed? When light is absorbed, energy from that light is also absorbed. This energy is transferred to electrons into a chemical molecule. Energy level of electrons are raised making photosynthesis happen

15. Quick Review In which organelle does photosynthesis occur? What light-absorbing molecule is used to gather sun’s energy? What are the reactants of photosynthesis? What are the products? Why do plants appear green? What are the two types of chlorophyll and what colors of the light spectrum do they absorb?

16. Inside a Chloroplast Thylakoids Saclike disc, photosynthetic membranes Contains photosystems – clusters of pigments and proteins that absorb light energy Granum Stack of thylakoids Stroma Region outside the thylakoid Place where Calvin cycle takes place

17. Electron Carriers What is a carrier molecule? A compound that can accept a pair of high-energy electrons and transfer them along with most of their energy to another molecule. NADP+ (nicotinamide adenine dinucleotide phosphate) – carrier molecule for photosynthesis (empty) NADPH is created when NADP+ gains 2 high energy electrons and a Hydrogen ion (full)

18. 2 stages of photosynthesis Light – dependent reactions Light – independent reactions (Calvin cycle)

19. Light – Dependent reactions Occurs in the thylakoid membrane Light energy is trapped by chlorophyll to split water molecules Oxygen gas is released, hydrogen continues on to combine with NADP+  NADPH + H ion (needed for dark reactions) The movement of electrons is known as the electron transport chain. Travels from photosystem II to photosystem I.

20. Light – Dependent reactions ATP synthase produces ATP by allowing H+ ions to pass through the thylakoid membrane. As the ions pass through, the ATP synthase rotates while binding ADP and a phosphate group together to produce ATP molecules.

21. Light-independent reactions (Calvin Cycle) Occurs in the stroma of the chloroplast Does not require light but will work in the light Uses the ATP and NADPH from the light- dependent reactions to produce high-energy sugars to break down carbon dioxide

22. Factors that Affect Photosynthesis Availability of water The lack of water slows down photosynthesis Temperature Slows at extreme temperatures and usually has an optimal temperature for each kind of plant Intensity of light Increases with light intensity up to a certain point, then levels off