2. How does a seed grow into a tree? Where does all the mass come from???

3. Photosynthesis

4. Plants convert the energy of sunlight into the energy of chemical bonds of carbohydrates

5. Importance of Photosynthesis Provides energy for plants Provides energy for animals that eat plants Provides energy for animals that eat animals that ate plants Provides energy for organisms that break down all of the above Provides the energy for most ecosystems on earth

6. But that ’ s not all.. Gives us food Provides wood, paper, other wood based products Provides cotton, hemp, other fibers Is the original source of energy in coal and oil Plants are pretty

8. But wait, there ’ s more.. Photosynthesis consumes Carbon Dioxide And Produces Oxygen

9. Photosynthesis: 6 CO 2 + 6 H 2 O C 6 H 12 O 6 + 6 O 2 carbon dioxide + water = sugar + oxygen STARCH photosynthetic products often stored as starch Starch = glucose polymer

10. CO 2 +H 2 0C(H 2 O)+ O 2 Photosynthesi s Respiration Sun The BIG Picture

11. Leaf Structure cuticle - waxy, water resistant layer on the surface of the leaf Epidermis - transparent, colourless cell layer below the cuticle mesophyll cells - pallisade: are elongated cells located just below the epidermal tissue - spongy mesophyll consists of loosely packed cells where gas exchange takes place

12. Fig. 10.2a

13. Leaf structure

14. Chloroplasts

15. Fig. 10.2b

16. Chloroplasts plant cell organelles where photosynthesis takes place, found mainly in mesophyll layers in leaves have an inner and outer membrane the liquid material in the chloroplast is called the stroma Stroma contains a series of membrane bound sacs called thylakoids which are stacked on top of one another to form grana adjacent grana are linked together by lamellae

17. Photosynthesis occurs partly within the stroma and partly within the thylakoid membrane The thylakoid membrane contains light-gathering pigments and an electron transport chain Thylakoid membranes enclose an interior space called the thylakoid lumen

18. Overview of Photosynthesis 1. Light reactions 2. Dark reactions – Calvin Cycle

20. The light reaction Light energy is being converted to chemical energy in the form of ATP and a reduced electron carrier (NADPH + H + )

21. Light Reactions Energy from sunlight is trapped, water molecules are split, NADPH and ATP are formed, O2 is given off as a waste gas

23. Fig. 10.4

24. When light strikes an object it can be: 1)Reflected 2)Transmitted 3)Absorbed Substances that absorb light are called pigments Different pigments absorb at different wavelengths

26. Pigments Substances that absorb certain wavelengths of light and reflect other wavelengths Thus they are coloredExamples:Chlorophyll (a and b) – greenCarotene – red/orangeXanthophylls - yellow

27. Chlorophyll Chlorophyll is a pigment that absorbs in the red and blue regions of the visible spectrum Most of the green wavelengths are reflected so a sample of chlorophyll appears green

28. Chlorophyll Absorbs red & blue light Reflects green light

29. Fig. 10.8

31. (A) When a molecule absorbs the energy of a photon, it is raised from a ground state to an excited state. (B) In the excited state, an electron is boosted to a more distant shell, where it is held less firmly.

32. Fig. 10.6

34. Energy Transfer and Electron Transport - Rather than being lost as fluorescence, energy from a photon may be transferred from one pigment molecule to another. In an antenna system, an excited pigment molecule can transfer energy through a series of other pigment molecules to a pigment molecule in the reaction center. That molecule may become sufficiently excited that it gives up its excited electron, which can then be passed on to an electron acceptor.

35. Chlorophyll Absorbs light and excites electrons Passes those electrons to an electron acceptor: NADP+ (nicotinamide adenine dinucleotide phosphate) NADP+ + e− → NADPH + H+

37. Energy Storing Compounds Energy trapped by molecules can be used to lift electrons to a higher energy level. From that higher energy level the electrons can fall down to their original energy level and do work along the way. Example – a solar cell that powers a calculator

38. Or … The high-energy electrons can be bound to an electron carrier. Nicotinamide Adenine Dinucleotide Phosphate NADP+ accepts a pair of high energy electrons and a Hydrogen ion to become NADPH

39. light-independent reactions do not use light directly, but instead use ATP, NADPH + H+ (made by the light reactions), and CO2 to produce sugars. There are three different forms of the light-independent pathway that reduces CO2: the Calvin cycle, C4 photosynthesis, and crassulacean acid metabolism.light-independent reactionslight reactionsCalvin cycleC4 photosynthesis crassulacean acid metabolism

40. Calvin Cycle Products from the light reactions and CO 2 from the atmosphere are used to produce carbohydrates

41. History Jan Van Helmont Found the mass of a pot of soil and a seedling. Watered the seedling for five years. Found the mass again Concluded that the increase in mass came from water

42. History Joseph Priestly Found that a candle goes out when placed in a jar. However, the candle keeps burning if a sprig of mint is also placed in the jar. Concluded that plants produce [Oxygen]

43. History Jan Ingenhousz Showed that Priestley ’ s experiment only works in the light. Concludes that light is necessary for plants to produce oxygen

44. CO 2 +H 2 0 C(H 2 O)+O 2 Chemical basis of photosynthesis Light

48. Transport in the Xylem Transport in the xylem may be due to a pushing force or a pulling force Pushing xylem sap is called root pressure

49. Root Pressure Root cells expend energy to pump mineral ions into the xylem Water may then flow down a concentration gradient (called root pressure) Not very efficient- can only push water 1-2m This is the cause of morning dew

50. Pulling Xylem Sap Water rises against gravity from the roots to the leaves without a pump (can rise 100m!) A maple tree may lose more than 200L of water per hour on a hot summer day by transpiration Transpiration is the evaporation of water from the aerial parts of plants, leaves but also stems, flowers and roots

51. Transpiration Mass flow is caused by the decrease in hydrostatic (water) pressure in the upper parts of the plants due to the diffusion of water out of stomata into the atmosphere Water is absorbed at the roots by osmosis, and any dissolved mineral nutrients travel with it through the xylem

52. Transport When plants evolved to live on land, vascular tissues evolved that could transport water (called the xylem) and sugar (called the phloem) from the highest leaf to the lowest root cell

53. -a system of tubes and cells that transport water and minerals from the roots to the leaves and carry carbohydrates from the leaves to other parts of the plant, including the roots Xylem cells - conduct water and minerals from roots to leaves Phloem cells -conduct food from leaves to rest of the plant Vascular bundle: vein

54. Autotrophs Self-feeders: –sustain themselves without eating or decomposing other organisms Plants are photoautotrophs –They use light Some bacteria are chemoautotrophs –Produce organic compounds without light from substances such as S or NH 3

55. Heterotrophs Live on compounds produced by other organisms Eat other plants or animals or are decomposers (bacteria or fungi) that eat fallen leaves, feces, dead animals

56. Light Form of electromagnetic radiation that travels at 3x10 8 m/s in wave packets called photons Light energy originates at the sun when 4H atoms combine to form 1 He atom The resulting mass is less than expected The lost mass has been converted to energy as predicted by E=mc 2 Each minute 120 million tons of solar matter is converted to energy Small amounts of this energy reaches the earth Our atmosphere screens out a lot of the electromagnetic spectrum but lets visible light through