1 / 35

Photosynthesis

Photosynthesis. Bio I Rupp. Focusing Questions. Where does the energy to do work come from? What chemical do cells use for energy? What is the equation for photosynthesis? How are chloroplasts arranged? What is NADPH? What are the two reaction pathways in photosynthesis?. Energy.

carsyn
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 Bio I Rupp

  2. Focusing Questions • Where does the energy to do work come from? • What chemical do cells use for energy? • What is the equation for photosynthesis? • How are chloroplasts arranged? • What is NADPH? • What are the two reaction pathways in photosynthesis?

  3. Energy • Light or solar energy is converted to chemical energy • This occurs in the chloroplast of plants • Plants • Blue-green algae • Photosynthetic bacteria

  4. History of Photosynthesis • Jan van Helmont • Belgian Physician • 1643 • Willow tree experiment • What caused the tree to gain weight?

  5. History of Photosynthesis con’t. • Joseph Priestley • English minister and chemist • 1771 • Candle experiment • What did the plant produce?

  6. History of Photosynthesis con’t. • Jan Ingenhousz • Dutch scientist • 1779 • Repeat of Priestley’s work • Plants only functioned in what?

  7. History of Photosynthesis con’t. • Based on the experiments of van Helmont, Priestley, and Ingenhousz, what three things can we say plants need/produce?

  8. Photosynthesis Equation • CO2 + H2O + Light C6H12O6 + O2

  9. Leaf Structure • Epidermis—outer cells of leaf • Palisade mesophyll—where the majority of chloroplasts are located • Spongy mesophyll—some chloroplasts are located here

  10. Leaf Structure con’t. • Xylem—water transport • Phloem—food transport • Cuticle—waxy covering that stops evaporation of water from the leaves • Stoma—opening in leaf that allows CO2 to enter

  11. Chloroplast structure • Stroma—the fluid interior that surrounds the other chloroplast structures • Granum—stacks of disk shaped thylakoids • Thylakoids—the site of photosynthesis

  12. Chloroplast structure con’t. • What makes the chloroplasts green? • Pigments • Chlorophyll a (650-700nm and 400-450nm) • Chlorophyll b (450-500nm and 650nm) • Carotenoids (450 nm) • Xanthophyll (600nm)

  13. How does Photosynthesis Work? • Light is captured • Light energy is converted to chemical energy • The chemical energy is a combination of • ATP • NADPH • Sugars • Light reaction pathways • Dark reaction pathways

  14. Light Reactions • Step one • Light hits photosystem II and boosts electrons to higher energy level • H+ ions are transported to create a concentration gradient • ATP is produced

  15. Light Reactions con’t.

  16. Light Reactions con’t. • Step Two • Low energy electrons enter photosystem I and is re-energized • The re-energized electrons then move into the NADPH electron chain

  17. Light Reactions con’t.

  18. Restoring Photosystem II • If electrons keep moving out where are the initial electrons coming from? • Water splitting reaction

  19. H+ ions and ATP Creation • How did H+ ions move across the thylakoid membrane? • They were pumped by ATP synthase • Facilitated diffusion

  20. Dark Reactions • Also known as the Calvin Cycle or Light Independent reactions • The ATP and NADPH from the light reactions is used to turn CO2 into sugar

  21. Dark Reactions con’t. • Step one • Carbon fixation • CO2 is attached to a 5 carbon sugar called ribulose bisphosphate (RuBP) • The resultant molecule is unstable and splits into two 3-carbon molecules of PGA

  22. Dark Reactions con’t. • Step two • Reduction • ATP and NADPH are used to rearrange the two 3-carbon molecules of PGA

  23. Dark Reactions con’t. • Step three • Regeneration of RuBP • Two of the PGAL molecules are used to make glucose • The remaining PGAL is rearranged, with the help of ATP, to RuBP

  24. Photosynthesis Overview

  25. Alternative pathways • C3 plants • Fix carbon to RuBP via the enzyme rubisco • Rubisco is probably the most abundant enzyme on Earth • If CO2 levels drop then the Calvin Cycle is starved • Photorespiration

  26. Alternative Pathways con’t. • C4 plants • CO2 is fixed into a 4-carbon compound • The mesophyll cells store the CO2 to keep feeding the Calvin Cycle • Slows down photorespiration • Good method for plants in hot climates

  27. Alternative Pathways con’t. • CAM plants • Crassulacean acid metabolism • CO2 is gathered at night and stored • CO2 can be released to keep the Calvin Cycle running • Photorespiration decreases

  28. Factors Affecting Photosynthesis • Light intensity • CO2 levels • Temperature

More Related