1 / 44

Photosynthesis

Photosynthesis. Why is Photosynthesis Important??. Provides Oxygen to almost all organisms need to break down food into energy(cell respiration-remember this for chapter 7). Review of Plant Cell Structure. Pic. Photosynthesis.

akamu
Download Presentation

Photosynthesis

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Photosynthesis

  2. Why is Photosynthesis Important?? • Provides Oxygen to almost all organisms need to break down food into energy(cell respiration-remember this for chapter 7)

  3. Review of Plant Cell Structure • Pic

  4. Photosynthesis • Converts radiant energy into chemical energy stored in the bonds of organic compounds • Stored in plants as STARCH • Done by Autotrophs • Done in the Chloroplasts of the plant cell

  5. I. The Chemistry of Photosynthesis • The chemical reactions of photosynthesis and respiration are opposites • Photosynthesis • CO2 + H2O+Energy  C6H12O6 + O2 • Respiration • C6H12O6 + O2  CO2 + H2O + Energy

  6. A. Energy Intermediates • ATP-ADP • NADPH- NADP+ (+) H+ • NADH- NAD+ (+) H+ • FADH2- FAD+ (+) 2H+

  7. ATP: Adenosine Triphosphate • Three Pieces: • Adenine • Ribose • Phosphate group

  8. The adenine and ribose combine to make Adenosine • The energy obtained from ATP comes from the breaking apart of phosphate groups • Pic Phosphorylation

  9. B. The ATP-ADP Cycle • When the cell needs energy from a specific activity… • 1. The outermost phosphate of ATP is broken off by the enzyme ATPase • 2. This phosphate group is transferred to another molecule in the process called PHOSPHORYLATION: when a phosphate group is added to a molecule.

  10. 3. The ADP then undergoes phosphorylation with the help of ATPsynthase to form a new ATP

  11. Turning ADP into ADP • Done with the aid of a proton pump Movement of Hydrogen Ions across the membrane …. • provides the energy needed to add a phosphate group to the ADP, creating ATP • This is done by active transport

  12. Characteristics of Light • Pic • Humans can see light between the wavelengths 400nm and 700nm • Other organisms can see light at different wavelengths than we can!

  13. Plants absorb light the best when the light is at a wavelength of around 450 or around 650nm • Plants do not absorb light between 500 and 600nm very well. • So, why are plants green??

  14. Where does photosynthesis happen? • Inside Chloroplasts • Specifically within the GRANA • Stacks of flattened sacs • Each stack is made of single sacs called Thylakoids. Side Note: Single Stack is called Granum

  15. STRUCTURES

  16. Thylakoids • Site of light absorption, where chlorophyll is found • Membrane of double lipid layers • Embedded with proteins like ATPsynthase It is very important to keep track of where things happen in photosynthesis • Some things happen between the two thylakoid membranes, in a space calleds the thylakoid space • Some things happen on the membranes of the thylakoid, and these products are released into the Stroma: Protein rich solution around the grana

  17. II. Stages of Photosynthesis • Divided into 3 sets of reactions: • 1. Light absorbtion by chlorophyll • 2. Light dependent reactions • A. electron transfer • B. Chemiosmosis • 3. Light independent reaction

  18. 1. Light absorbtion by chlorophyll • Radiant energy from the sun is absorbed by pigments Chlorophylls • Chlorophyll a- most like absorbtion • Chlorophyll b- some light absorbtion

  19. In the Chloroplasts • Accessory Pigments: • Carotenoids- absorb some green and reflect yellow/orange • They and chlorophyll b send absorbed light energy to chlorophyll a

  20. 2. Light Dependent Reaction • Light Reactions Convert the light energy to chemical energy 2 Main Stages: A. Electron Transport- Converts the suns energy to electrical energy B. Chemiosmosis- Converts the electrical energy to chemical bond energy

  21. A. Electron Transfer Sunlight strikes the chlorophyll molecules and “excites” (e-) Photosystems: are units of several hundred chlorophyll molecules and carrier molecules. The photosystems are found in the: Thylakoid Membrane

  22. The reaction starts in Photosystem II • Sunlight strikes chlorophyll in photosystem II, and excites the e- e- move down chain of Electron Carriers(ETC)

  23. 2. e- move from high energy to a lower energy level found in photosystem I • ** Giving off energy

  24. 3. At the same time… • Light strikes photosystem I • E- are excited and move along a transport chain • E- leaving photosystem I are replaced by those from photosystem II

  25. 4. The energy is converted to energy intermediates: • A. NADPH is formed when the electron from photosystem I causes NADP+ to bond with H+ *E- lost in Photosystem II are replaced by electrons taken from water molecules When H20 splits… • hydrogen is used to make NADPH and ATP

  26. Oxygen is given off as waste product: This is where you get all of the oxygen that you breathe!! • Pic

  27. B. Chemiosmosis • The diffusion of chemicals through a membrane resulting in the formation of ATP • 1. During the breakdown of water, there is a build up of H+ ions in the thylakoid space

  28. 2. The movement of H+ ion across the thylakoid membrane triggers the phosphorylation of ADP to ATP Done by ATP synthase • 3. The ATP formed in the stroma is used in the 3rd reaction, during Carbon Fixation

  29. What do we get out of the light reactions?? • ATP, produced in the stroma • NADPH, produced in the stroma • Hydrogen ions, produced in the thylakoid space, pumped into the stroma to make NADPH and ATP • Oxygen, given off as by-product(waste_

  30. 3. Light Independent Reaction: Calvin Cycle(Dark Reactions) Uses the energy formed in the light dependent reaction(ATP and NADPH) to form organic compounds. There are three possible pathways that can be followed- depends on the plants environment. • A. Calvin Cycle or C3 • B. C4 Pathway • C. CAM cycle

  31. A. The Calvin Cycle(C3): The most common form of carbon fixation • 1. CO2 diffuses into the stroma and an enzyme on the thylakoid membrane binds to CO2 to a five carbon – Ribulose Biphosphate molecule(RUBP)= 6 carbon molecule • 2. The 6C molecule is unstable so it splits in to 2 PGA’s- Phosphoglyceric Acid(3C)

  32. 3. The 2 PGA’s get a phosphate from ATP and H from NADPH to form Phosphoglyceraldehyde(PGAL)(G3P), ADP and NADP • 4. Most of the PGAL regenerates more RuBP. This is done by using ATP. The other PGAL is used to produce carbohydrates. • Every turn of the Calvin Cycle drops off 1C. So 3 turns per G3P. Two (G3P’s) produces a glucose molecule. 6 turns total.

  33. Pic of cycle from other notes

  34. B. C-4 Pathway • Carbon Dioxide is bound to a compound to form a four-carbon intermediate that enters the C-3 pathway • Fixes carbon 4 times faster than the C-3 pathway- allows plants to grow more quickly • Requires more energy than the C-3

  35. Key Feature: The light dependent reactions and the Calvin Cycle occur in different areas of the leaf.

  36. Many desert plants are C-4 • Example Corn, Sugar Cane • C-4 occurs in sunny areas

  37. C. CAM- Crassulacean acid metabolism • Plants take in CO2 at night and store it • Used in the daytime in The Calvin Cycle • Prevents excess water loss • Key Feature: The light dependent reactions and carbon fixation occur at different times.

More Related