Photosynthesis: Life from Light and Air

2. Photosynthesis:LifefromLight andAir

3. Energy needs of life • All life needs a constant input of energy • Animals = Heterotrophs • get their energy from “eating others” • eat food = other organisms = organic molecules • make energy through respiration • Plants = Autotrophs • get their energy from “self” • get their energy from sunlight • build organic molecules (food) from CO2 • make energy through photosynthesis

4. carbon dioxide + water + energy  glucose + oxygen light energy  6CO2 + 6H2O + + 6O2 C6H12O6 Photosynthesis This is the equation you are used to seeing, but this is not the whole story…

5. ATP What is the main chemical fuel that most living organisms use to store energy? • ATP – adenosine triphosphate What does an ATP molecule consist of? Adenine, ribose, and three phosphate groups What do the lines between the parts of the molecule represent? Chemical bonds

6. WHAT IS THE ROLE OF ATP IN CELLULAR ACTIVITIES? • The characteristics of ATP make it an exceptionally useful molecule that is used by all types of cells as their basic energy source

7. Even though ATP is very efficient at transferring energy, it is not very good for storing energy over the long term. • Living organisms store large amounts of energy in the form of glucose (90 times more energy than ATP) • Cells can break apart glucose and make ATP molecules very easily to release the energy slowly

8. How do plants live? • Photosynthesis • Energy building reactions • collect sun energy • make ATP • Sugar building reactions • use ATP for energy • use CO2 as carbon for new sugars • build sugars • glucose, cellulose, starch • build all other organic molecules • proteins, lipids, carbohydrates, DNA • store energy for future use • starch in seeds & roots

9. sun CO2 Photosynthesis • Actually 2 separate reactions • Energy building • use sunlight • make energy (ATP) • Sugar building • use ATP • use CO2 • make sugars (C6H12O6) Energybuilding reactions ATP ADP Sugarbuilding reactions sugar

10. CO2 Chloroplasts absorbsunlight & CO2 Leaf Leaf Chloroplasts Chloroplasts contain Chlorophyll Chloroplast makeenergy & sugar

11. Energy Building Reactions light energy  H2O + + O2 ATP H2O • makes ATP energy • releases oxygenas a waste product sunlight Energy Building Reactions ATP O2

12. Sugar Building Reactions  CO2 + + ADP C6H12O6 ATP • builds sugars • uses ATP • cycles ADP back to make more ATP CO2 ADP SugarBuilding Reactions ATP sugars C6H12O6

13. light energy  CO2 + H2O + + O2 C6H12O6 Putting it all together H2O CO2 Plants make both: • ATP • sugars sunlight ADP SugarBuilding Reactions Energy Building Reactions ATP sugars C6H12O6 O2

14. WHAT IS THE ROLE OF CHLOROPHYLL IN PHOTOSYNTHESIS? • In addition to water and carbon dioxide, photosynthesis requires light and chlorophyll, a molecule in chloroplasts • Sunlight, which your eyes perceive as “white” light, is actually a mixture of different wavelengths of light of various colors

15. Any compound that absorbs light also absorbs energy from that light. When chlorophyll absorbs light, much of the energy is transferred directly to electrons in the chlorophyll molecule, raising the energy levels of these electrons. These high-energy electrons make photosynthesis work HOW WELL WOULD A PLANT GROW UNDER PURE YELLOW LIGHT? The plant would not grow well because neither chlorophyll a nor b absorbs much light in the yellow region of visible light

16. 8-3 THE REACTIONS OF PHOTOSYNTHESIS • Take a look at the picture of a chloroplast on page 208 • Photosynthesis is broken down into two reactions • light-dependent reactions- occur in thylakoid membrane • light-independent reactions (Calvin Cycle) – occur in the stroma

17. WHAT HAPPENS IN THE LIGHT-DEPENDENT REACTIONS? • The light-dependent reactions produce oxygen gas and convert ADP and NADH+ into the energy carriers ATP and NADPH • NADP+ - a carrier molecule that can accept a pair of high-energy electrons and transfer them along with most of their energy to another molecule; NADP+ converts to NADPH when it accepts electrons

18. WHAT IS THE CALVIN CYCLE? • The Calvin Cycle uses ATP and NADPH from the light-dependent reactions to produce high-energy sugars

19. Factors that can affect photosynthesis • water • temperature • intensity of light

20. light energy  6CO2 + 6H2O + + 6O2 C6H12O6 So what does a plant need? • Bring In • CO2 • H2O • light • Let Out • O2 • Move Around • sugars leaves shoot roots

21. xylem (water) phloem (sugar) cuticle epidermis palisades layer spongy layer stomate guardcell Leaf Structure O2 H2O CO2 • gases in & out • water out • transpiration O2 H2O CO2

22. Stomates • Function of stomates • CO2 in • O2 out • H2O out guard cell stomate

24. Xylem carry water up from roots

25. Phloem: food-conducting cells • carry sugars around the plant wherever they are needed • new leaves • fruit • seeds

26. Putting it all together • Making a living… • sunlight • leaves = solar collectors • photosynthesis • gases: CO2 in & O2 out • stomates = gases in & out • H2O • roots take in water from soil • pulled up by leaf evaporation • nutrients • roots take in from soil

27. + water + energy  glucose + oxygen carbon dioxide glucose + oxygen  carbon + water + energy  C6H12O6 + 6O2 6CO2 + 6H2O + ATP dioxide light energy  6CO2 + 6H2O + + 6O2 C6H12O6 How are they connected? Respiration Photosynthesis

28. sun glucose H2O The Great Circleof Life! Where’s Mufasa? Energy cycle Photosynthesis plants CO2 O2 animals, plants Cellular Respiration ATP

29. air The poetic perspective • All of the solid material of every plantwas built out of thin air • All of the solid material of every animal was built from plant material sun Then all the cats, dogs, mice, people & elephants…are really strands of air woven together by sunlight!

30. Any Questions??