1. Chapter 8 Photosynthesis

2.  Energy  the ability to do work  1 st law of thermodynamics  Not created nor destroyed  Transferred or transformed  2 types  Potential  stored energy based on position or composition  Kinetic  energy of motion

3.  Energy used by cells is stored in ATP  Adenosine triphosphate  Release energy by breaking bond between 2 nd and 3 rd phosphate  Makes ADP  Can be recharged

4. Obtaining ATP  Autotrophs  Make their own food  Photosynthesis – use sunlight to make food  Heterotrophs  gain energy by consuming other organisms

5. Overview of Photosynthesis  Life depends on light from the sun (mostly)  Seen as white light  mixture of ROY G. BIV  Plants gather light using pigments  Light capturing molecules  Chlorophyll is most important pigment  Reflects green light. Absorbs blue-violet, & red

6.  Plants contain chloroplasts  Thylakoid  photosynthetic membrane sac  Stacks called grana  Many grana/chloroplast  Stroma  fluid outside of grana Picture on page 231

7. Energy collection  Chlorophyll collects light energy  Transfers energy to electrons  high energy electrons  Needed to power photosynthesis  Carrier molecules are used to move high energy e -  NADP +  NADP + holds 2 h e e - s and on hydrogen ion  becomes NADPH  e - are transported to rxn sites to build carbohydrates like sugar.

8. Overview  Photosynthesis uses light from the sun to convert water and carbon dioxide into high energy sugars and oxygen.  Sugars put together to form starch

9. Light-dependent reactions  Involve light and pigments  Use of sunlight to make energy rich compounds like ATP  Take place in the thylakoid membrane  Water is required and oxygen is given off.

10. Light-independent reactions  ATP and NADPH (from light dependent reactions) are used to make sugar from CO 2.  No light required  Take place in the stroma  Outside of the thylakoid.

11. Photosynthesis overview  Light dependent reactions  Use energy from light to produce oxygen  ADP  ATP  NADP +  NADPH  Light independent reactions  ATP and NADPH from above are used to make high energy sugars

12. Light dependent reactions  Take place in the thylakoids  Contain groups of chlorophyll and proteins called photosystems (PS)  PS absorb light energy.  Photosystem II  Light energy raise electrons to high energy state  Water is split to give electrons back to PS II  Oxygen is produced  Electrons go to the electron transport chain (ETC)  Energy from electrons is used to pump Hydrogen ions into the thylakoid  Electrons then pass to photosystem I

13.  Photosystem I  Electrons are recharged  Electrons go through ETC I  2 electrons and 1 hydrogen ion are added to NADP + to make NADPH  NADPH is used in the light independent reactions

14. ATP formation  Hydrogen ions are highly concentrated inside the thylakoid  To balance H + ions must leave the thylakoid  Leave through ATP synthase  As the H + ions leave ATP synthase rotates  Rotation turns ADP into ATP  ATP sent to light independent reactions.

16. Light independent reactions  AKA Calvin cycle  ATP and NADPH have a lot of energy but are bad at storing it 1.CO2 enters the leaves through pores 2.Carbon is “fixed” to form organic molecules a)6 CO2 molecules join w/ 6 – 5C molecules to make 12 – 3C molecules b)12 ATP and 12 NADPH are used to transform the carbon molecules into different molecules c)½ way through 2-3C molecules leave the cycle to become glucose d)The other 10-3C molecules stay in the cycle and are transformed back into the 6-5C molecules we started with.  6 ATP are used

17. Summary of the Calvin Cycle  Allows for the production of glucose and organic molecules  18 ATP  18 ADP  12 NADPH  12 NADP +

18. Factors affecting photosynthesis 1.Temperature  Enzymes function best between 0°C and 35° C 2.Light intensity  Higher light intensity increases the rate of photosynthesis up to a point 3.Availability of water  Lack of water slows photosynthesis  Desert plants have wax coatings or different pathways

19. Extreme photosynthesis  C4 photosynthesis  Capture low levels of CO 2 and send them to the Calvin cycle  Forms a 4 carbon molecule  Uses extra energy  Corn, sugar cane, sorghum  CAM plants  Crassulacean acid metabolism  Only let air in at night  Make CO 2 into organic acids  Pineapple trees, desert cacti, and ice plants