3. Leaf Structure Palisades – capture light energy (photosythesis) Spongy – captures light energy and allows for circ. of gases Epidermis – protects leaf from dehydration and disease Cuticle – produced by epidermis –made of lipid Vein – brings water to leaves and transports sugar away from leaves Stomates – lets in CO2 – lets out O2 and H2O Guard Cells – opens and closes stomates

4. Structure/Function Relationships in the Leaf  Palisades – main photosynthetic cells – lined up so more fit/at top for better light absorption  Epidermis – protect leaf from disease and dehyration because it is on the very outside of the leaf and is rectangular so they fit together tightly and do not allow anything to pass between the cells. They secrete the cuticle which is made of lipids and is non- polar and therefore seals the cells so that no water which is polar can go through  Stomates – holes that let CO2 in and O2 out – some on top, most on bottom, controlled by guard cells. This allows them to let the gas exchange happen without losing too much water vapor. When really hot and dry, guard cells can close them and at night when can’t photsynthesize anyway without the light. Also, by being on bottom which is cooler – lose less water

5. Structure/Function Cont.  Spongy – away from sun but still maximize overall light absorption by providing more chloroplasts/ at bottom near stomates where most of CO2 enters so it can more easily circulate and get to all of the cells that are photosynthetic since don’t want too many stomates on top  Veins- in the middle to supply water to and pick up food from the photosynthetic cells. Made of many cells instead of being hollow to maximize adhesion to move the water from roots to leaves without supplying energy

6. Chloroplast Structure Thylakoid Thylakoid – Flattened sacs made of membranes Contains chlorophyll and electron carriers Site of light reactions Grana Grana – Stack of Thylakoids Stroma Stroma – liquid part around thylakoids Contains enzymes for Calvin Cycle Contains DNA, RNA, and ribsomes so chloroplast can make few of its own proteins Chlorophyll Chlorophyll – Colored pigment that absorbs the sun’s energy Absorbs red and blue visible light and reflects mainly green

7. Thylakoid Membrane – has chlorophyll embedded for maximum light absorption and ordering of reactions Light reactions take place here Grana – stack of thylakoids Stroma – fluid in between the thylakoids – like the cell’s cytoplasm Has all the enzymes for the Calvin cycle, DNA, RNA, and ribosomes

8. Electromagnetic Spectrum

9. Photosynthesis Equation CO 2 + H 2 O → Glucose + O 2 Chlorophyll Light energy Light Reactions 1.Chlorophyll absorbs blue and red visible light which excites the electrons in the hydrogen atoms of chlorophyll. 2.The excited high energy electrons jump off and attach to positively charged carriers. The hydrogen protons are dragged along.

10. Light Reactions Continued 1.H 2 O is split by light energy and enzymes put the hydrogens (including their electrons) onto chlorophyll to replace the ones that left. 2.The Oxygens that are left from the splitting of H 2 O go off into the atmosphere.

11. Calvin Cycle - Making Sugar CO 2 + CO 2 + Hydrogens with high energy electrons Hydrogens with high energy electrons (from chlorophyll) Sugar Sugar ↓

12. Calvin Cycle - Making Sugar CO 2 + RuBP + CO 2 + RuBP + Hydrogens with high energy electrons Hydrogens with high energy electrons 5-Carbon Molecule (from chlorophyll) RuBP + Sugar ↓

13. Summary Equation Which part of the equation comes from the light reactions and which parts are from the Calvin Cycle? CO 2 + H 2 O → Glucose + O 2 Chlorophyll Light energy Light Calvin

14. Why Can’t The Calvin Cycle Happen At Night?  You need the high energy electrons from the light reactions and you can’t get them without the light.  The stomates close at night to conserve water and no CO2 is available  Rubisco – the enzyme that puts CO2 on RuBP is light sensitive.

15. What Effects the Rate of Photosynthesis?  Temperature  Light Intensity  CO 2 O2O2O2O2  pH Photorespiration – O2 competitively inhibits the first chemical reaction of the Calvin Cycle so no CO2 can enter the Calvin cycle therefore there is no photosynthesis and the CO2 is just given off

16. What Effects the Rate of Photosynthesis?  Temperature  Light Intensity  CO 2 O2O2O2O2  pH Photorespiration – O2 competitively inhibits Rubisco so no CO2 can enter the Calvin cycle therefore there is no photosynthesis and the CO2 is just given off

17. Leaf and Cellular Adaptations to Hot Dry Climates C4 Plants  Sugar Cane, Corn, Grass  Different cellular arrangement in the leaf  A different enzyme not inhibited by oxygen initially fixes the carbon dioxide CAM  Cactus, succulents  Open stomates at night and collect CO2  CO2 binds to an organic acid which stores the CO2  During the day when the products of the light reactions are available`, CO2 is released from the organic acid and the Calvin Cycle proceeds