1 / 45

Photosynthesis

Photosynthesis. LA Charter School Science Partnership 3 March 2012 Nick Klein. Today’s Talk. Intro Part 1: Photosynthesis – the big picture Part 2: Chemistry of photosynthesis Part 3: Biology and ocean context. Today’s Talk cont’d.

fisseha
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 LA Charter School Science Partnership 3 March 2012 Nick Klein

  2. Today’s Talk • Intro • Part 1: Photosynthesis – the big picture • Part 2: Chemistry of photosynthesis • Part 3: Biology and ocean context

  3. Today’s Talk cont’d • I’ve split this talk into three (roughly) even parts. We will take a brief (1-2min) break between sections. Please feel free to take notes, handle the props, think of questions for after the talk, etc.

  4. Part 1: The big picture • What is photosynthesis? Let’s define it! • Photosynthesis is the process by which organisms use the energy in sunlight to chemically transform carbon dioxide (CO2) into organic carbon compounds such as sugars • Some organisms can use energy sources other than sunlight, this is called chemosynthesis (Jason’s talk!)

  5. Part 1: The big picture • Organisms that make their own food are called autotrophs. Organisms that make food using photosynthesis are photoautotrophs • All animals, including humans, are heterotrophs—we have to consume other organisms as food

  6. Part 1: The big picture • Why is photosynthesis important? • Most life on Earth depends on it • Responsible for us having oxygen to breathe! • Fossil fuels are derived from ancient photosynthesis • Photosynthesis removes CO2 from the atmosphere

  7. Part 1: The big picture

  8. Part 1: The big picture • Photosynthesis uses sun energy to transform inorganic carbon dioxide (CO2) into organic carbon compounds such as sugars, fats, and amino acids… the building blocks of life! • Scientists refer to this conversion as “fixing” carbon. So, photosynthesis is sun-driven carbon fixation.

  9. Part 1: The big picture • Photosynthesis involves reduction/oxidation (redox) reactions— chemical reactions that involve the movement of electrons from one molecule to another • In photosynthesis, when carbon dioxide is fixed, it is reduced (electrons are added to it) which produces organic carbon compounds

  10. Part 1: The big picture Loss ofElectrons isOxidation goesGain ofElectrons isReduction

  11. Part 1: The big picture • Example: nitrogen fixation 2xnitrogen gas ammonia

  12. Part 1: Bonding on an atomic level • How many electrons in nitrogen gas? N N

  13. Part 1: Bonding on an atomic level • How many electrons in two molecules of ammonia? N H H H

  14. Part 1: The big picture • In photosynthesis, photoautotrophs use the energy of sunlight to fix carbon dioxide into glucose • Carbon dioxide is reduced to make the basic chemical building blocks of all life • Photosynthesis is one of the most important biological processes!

  15. Break!

  16. Part 2: Chemistry of photosynthesis • What (chemically) is required for photosynthesis? • Light • Water • Carbon dioxide 12H2O + 6CO2 C6H12O6 + 6O2 + 6H2O

  17. Part 2: Chemistry of photosynthesis • There are two distinct parts of photosynthesis • Light-dependent (light) reactions: sun energy is absorbed and transformed into chemical energy • Light-independent (dark) reactions: also called the Calvin cycle, chemical energy from the light reactions is used to fix CO2 into glucose

  18. Part 2: Chemistry of photosynthesis • Light-dependent (light) reactions can ONLY happen when there is sunlight available • Of course, the first step in transforming sun energy into chemical energy is to soak up some rays!

  19. Part 2: Chemistry of photosynthesis • Plants use pigments to absorb light energy from the sun • Main pigment is chlorophyll a (shown next slide), this is responsible for plants being green • There are many other accessory pigments which help plants harvest different colors of light

  20. Part 2: Chemistry of photosynthesis

  21. Part 2: Chemistry of photosynthesis anthocyanins

  22. Part 2: Chemistry of photosynthesis • The pigments, along with a large number of enzymes and other chemical machinery, form photosystems • Light energy is absorbed by the pigments inside the photosystem • This energy is used to split water molecules into electrons, protons, and oxygen gas

  23. Part 2: Chemistry of photosynthesis Pigments Photosystem 2H2O 4e- + 4H+ + O2

  24. Part 2: Chemistry of photosynthesis • The electrons we get from splitting water are then excited by more sun energy captured by the pigments and enter the electron transport chain • The electron transport chain is a series of different molecules each electron is passed along to. The electron loses some of its energy with each “step” it makes

  25. Part 2: Chemistry of photosynthesis Electron TransportChain Pigments Photosystem 4e-

  26. Part 2: Chemistry of photosynthesis • After passing through the electron transport chain, the photosystem attaches the electrons to a molecule called NADPH • NADPH is a reductant—it can reduce (give electrons) to other compounds • Where do you think the electrons from NADPH will go?

  27. Part 2: Chemistry of photosynthesis NADPH

  28. Part 2: Chemistry of photosynthesis Electron TransportChain Pigments Photosystem 4e- NADPH

  29. Part 2: Chemistry of photosynthesis • The energy from the electron transport chain is used to pump protons (the H+ we made from splitting water) through chemical machinery that makes ATP • The high-energy phosphate bonds in ATP are broken to provide the energy for most chemical reactions that occur in biology

  30. Part 2: Chemistry of photosynthesis ATP

  31. Part 2: Chemistry of photosynthesis • Light-dependent (light reactions) summary: light is captured by pigments and used to split water, ultimately producing oxygen gas, NADPH (a reductant) and ATP (energy)

  32. Part 2: Chemistry of photosynthesis

  33. Part 2: Chemistry of photosynthesis • Light-independent (dark) reactions can occur with or without light, they don’t require it • NADPH and ATP from the light-dependent reactions are used to reduce CO2 into sugars and other organic compounds

  34. Part 2: Chemistry of photosynthesis ATP + NADPH CO2 C6H12O6 The Calvin Cycle (light independent reactions)

  35. Part 2: Chemistry of photosynthesis

  36. Part 2: Chemistry of photosynthesis • Light-dependent (light reactions) summary: light is captured by pigments and used to split water, ultimately producing oxygen gas, NADPH (a reductant) and ATP (energy) • Light-independent reactions: ATP and NADPH are used to fix CO2 into organic carbon (sugars)

  37. Part 2: Chemistry of photosynthesis 12H2O + 6CO2 C6H12O6 + 6O2 + 6H2O C6H12O6 + 6O2 6H2O + 6CO2 Respiration is photosynthesis backwards!

  38. Break!

  39. Part 3: Broader context • We’ve gone over the basics and the chemistry of photosynthesis, let’s explore some of the biology and think about it in the context of the ocean and the Earth as a whole!

  40. Part 3: Broader context

  41. Part 3: Broader context • The overall trend of atmospheric CO2 is upward (it is increasing). Why is that? • Within each year, what is happening to the CO2? Why might this be? • The “wave” pattern is the Earth “breathing” in and out—lower CO2 in the summer when all the plants are growing and using it for photosynthesis!

  42. Part 3: Broader context • Land plants have stomata on the undersides of their leaves • They open their stomata to breathe in CO2. When might they want to open them? When would they close them?

  43. Part 3: Broader context

  44. Part 3: Broader context

  45. Part 3: Broader context • The oceans account for about half of all carbon fixation • However, the oceans only have 0.2% of the biomass • Fast turnover—what is the lifespan of a phytoplankton compared to a tree? • What about these facts might make algae interesting to scientists?

More Related