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Photosynthesis

8-1 Energy

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Photosynthesis

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    1. Photosynthesis

    2. 8-1 Energy & Life Energy is ability to do work All living things need energy Without energy, life would cease to exist Energy can be light, heat, electricity, & stored in chemicals

    3. Chemical Energy Living things must release ATP from compounds Adenosine triphosphate (ATP)

    4. The Generation of ATP ATP is generated by the phosphorylation of ADP (adding a PO4)

    5. Storing Energy In the form of ADP (adenosine diphosphate) Only has 2 phosphate groups When your cells need energy, they add a phosphate group to ADP & a little energy to make more ATP molecules Use glucose to store long term energy

    6. Releasing Energy ATP molecules have bonds between the phosphate groups ATP is the basic energy source for cells Your cell breaks the bond to release energy One breaking bond is enough energy to power active transport, protein synthesis, & cytoskeleton movement in a cell

    7. Biochemical Energy Na-K pump in the membrane pumps Na ions out & K ions in ATP provides the energy to do this ATP even provides the energy for fireflies to light up! Glucose is the primary source for ATP

    8. Autotrophs Organisms that make their own food. Example: plants, cyanobacteria, blue-green bacteria, algae make chemical energy from sunlight

    9. Heterotrophs Organisms must consume food (plants or animals) to obtain energy Example: animals, fungi, bacteria

    11. 8-2 Overview of Photosynthesis Process of converting water & carbon dioxide into high-energy carbohydrates (sugars & starches)

    12. How plants grow--Van Helmonts experiment Mass of dry soil & a seedling Watered plant for 5 years Seedling grew to 75 kg mass Mass of soil was almost unchanged He concluded most of the mass had come from the water Actually, the seedling received carbon dioxide from the air to make sugars to grow

    13. Joseph Priestly Glass jar over a candle & saw flame go out He reasoned there was something in the air that the flame needed He took a sprig of mint leaf & put it in the jar, after a few days he put the candle in & the flame stayed lit for a while He believed that the plant had made something (oxygen) that the flame needed

    14. Jan Ingenhousz Showed that the plant could only keep the flame lit if the plant was exposed to sunlight Proved sunlight was necessary for the plant to make oxygen *These experiments proved that plants, in the presence of sunlight will transform carbon dioxide & water into carbohydrates & oxygen

    15. Equation 6 CO2 + 6 H 2 O C6 H12 O6 + 6O2

    16. Light & Pigments In addition to water & carbon dioxide, photosynthesis requires light & chlorophyll, a molecule in chloroplasts Sunlight is actually a mixture of different wavelengths Plants gather the suns energy with light absorbing molecules called pigments

    17. Photosynthesis Movie

    18. Chlorophyll 2 types of chlorophyll absorbs different light wavelengths

    19. Green leaves Green light is reflected by leaves, so thats why they look green Plants also contain red & orange pigments such as carotene (in carrots) that absorb other light wavelengths When chlorophyll absorbs light, much of this energy is transferred to the electrons & raises the energy

    20. Pigments When carotene and chlorophyll occur in the same leaf, together they remove red and violet light from sunlight that falls on the leaf.

    21. Why do leaves change colors in the Fall?

    22. Take place inside the chloroplasts Thylakoids are saclike membranes arranged in stacks called grana Proteins in thylakoid organize chlorophyll & other pigments into clusters known as photosystems Photosystems collect light The Stroma is the fluid portion outside the thylakoids Photosynthesis

    23. Light movie

    24. 8.3 Process of Photosynthesis Light-dependent: take place in the thylakoid Light-independent (the Calvin cycle): take place in the Stroma, which is outside of the thylakoid membranes

    25. Electron Carriers Sunlight excites electrons in chlorophyll Electron Transport: electron carriers transport the electrons to other molecules NADP+ (nicotinamide adenine dinucleotide phosphate) can hold 2 high-energy electrons along with a H+ ion This forms NADPH (energy in chemical form)

    26. Light-dependent Reactions Require light to take place Produce Oxygen gas , ATP, & NADPH Step 1. Photosystem II absorbs light Enzymes on the thylakoid break up water molecules into 2 e - s, 2 H+s, and 1 O2 The plant uses the e-s & releases O2 into the atmosphere

    27. Step 2. Electron Transport Chain High-energy e-s move from photosystem II to photosystem I through the electron transport chain H+s are transported from stroma into inner thylakoid space

    28. Step 3. Photosystem I pigments use light energy to reenergize the e-s NADP+ transports the e-s & H+s to make NADPH

    29. Step 4: H+s pumped across membrane Inside becomes positively charged This provides energy to make ATP

    30. Step 5: ATP synthase allows H+s to pass through membrane ATP synthase is a protein that rotates like a turbine As it rotates, ADP is bond to a PO4 to make ATP

    31. Overall Light dependent Water, ADP, & NADP+ are used to produce Oxygen, 2 ATPs, & NADPH This gives energy to make sugars in a later process

    32. Light Dependent Needs light energy with chlorophyll to make the products ATP, NADPH, & oxygen in Thylakoid

    33. Light Dependent Movie

    34. Calvin Cycle Light-independent phase Uses ATP & NADPH from the light- dependent reactions to produce high-energy sugars Named after Melvin Calvin who received the Noble prize for his work

    35. Calvin Cycle Steps 3 CO2 molecules join to a 3 carbon molecule ATP & NADPH join the 3 carbon molecules to form the G3P molecules The cycle must repeat 6 times to form 1 glucose molecule The G3P molecules are joined to form glucose in the cytoplasm

    36. Calvin Cycle Summary Major molecules coming In & Out 6 Turns of the cycle produces 1 glucose molecule

    37. Calvin Cycle Light Independent stage in Stroma Uses ATP & NADPH that was produced in light dependent stage plus the CO2 to make the products high-energy sugars It take 6 cycles to convert 6 Carbon dioxides into 1 6-carbon sugar Glucose stores >90 times the energy stored by ATP

    38. Calvin Cycle Movie

    39. Photosynthesis Summary Definition of Photosynthesis:

    40. Factors Affecting Photosynthesis Water -- shortage slows it down Temperature-- best 0-35C, temps above or below, slows it down Light Intensity will increase the rate until the limit is reached (for that particular plant), then it plateaus

    41. Animated photosynthesis

    42. Extreme Conditions Tropics & Desert: extreme heat plants close the openings in their leaves to keep from drying out This also reduces the absorption of CO2 Some plants have adapted to these bright & hot conditions

    43. Special Plants C4 plants specialized chemical pathway to capture more CO2 (requires more ATP) EX: corn, sugar cane, & sorghum CAM plants Crassulacean Acid Metabolism allows air in only at night that combines to CO2 to form acids to trap the CO2 in their leaves Carbohydrates are then formed during the day The leaves are sealed with a waxy coating to prevent water loss during the day

    44. Putting it all together Animation

    45. Review The light dependent reactions occur in the Thylakoid membrane The Reactants of the light-dependent reactions are 6 H2O, sunlight, chlorophyll The products of the light-dependent reactions in photosynthesis are 6 O2, ATP, & NADPH

    46. Review The Calvin Cycle occurs in the Stroma The Reactants in the Calvin Cycle are 9 ATP, 6 NADPH, 6 CO2 The Products in the Calvin Cycle are 9 ADP, 6 NADP+, G3P 2 G3Ps are joined in a glucose molecule in the cytoplasm

    47. Standardized Prep pg 219 The principal pigment in plants is 2. Which of the following is NOT produced in the light-dependent reactions of photosynthesis?

    48. Standardized Prep pg 219 3. Which equation best summarizes the process of photosynthesis? 4. The color of light that is LEAST useful to a plant during photosynthesis is

    49. Standardized Prep pg 219 5. The first step in photosynthesis is the 6. In a typical plant, all of the following factors are necessary for photosynthesis EXCEPT

    50. Standardized Prep pg 219 7. Which pigment traveled the shortest distance? 8. A valid conclusion that can be drawn from this information is that spinach leaves

    51. Standardized Prep pg 219 9. In which organelles would most of these pigments be found?

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