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Photosynthesis -energy producing process in AUTOTROPHS -autotrophs are organisms that produce their own food they are “self feeding”, ex: plants, algae,

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Presentation on theme: "Photosynthesis -energy producing process in AUTOTROPHS -autotrophs are organisms that produce their own food they are “self feeding”, ex: plants, algae,"— Presentation transcript:

1 Photosynthesis -energy producing process in AUTOTROPHS -autotrophs are organisms that produce their own food they are “self feeding”, ex: plants, algae, some bacteria Making Your Own Food Requires: -the intake of sunlight energy -pigments (specifically Chlorophyll) found in cells of autotrophs capture the light and use it to start the photosynthesis reaction -Chlorophyll is found in chloroplasts and is what makes the plant green. -Most chlorophyll is found in leaf material so most of the photosynthesis that takes place happens in the leaf

2 The overall reaction for photosynthesis requires: sunlight water carbon dioxide (you exhale during respiration) And produces: sugar water oxygen (you inhale during respiration) Here’s how it all happens:

3 -white light colors are the colors of the rainbow…red, orange, yellow, green, blue, indigo and violet…ROYGBIV -chlorophyll in plants absorbs the ends of the spectrum better and reflects the green in the middle. That is why we see plants as being green…they reflect the green wavelength

4 First step is called the LIGHT REACTION: -as it’s name implies…it requires light!! -not just any light will do…it has to be a specific wavelength motqGgDk/s1600/Chlorophyll-Absorption-Spectrum.jpg -notice how light in the 500 to 600 nm range is not absorbed in any great amount…WHY? --green plant pigment prefers light in the 400- 450 nm range and the 600-680 range.

5 Light reaction: -uses sunlight to split water into H and O -sunlight is captured by the chlorophyll in a chloroplast -the energy in the light molecule is used to break apart water molecules and releases some heat -Oxygen that results from this split is given off as a by-product that you use to breathe -the Hydrogen is “captured” by an enzyme, NADP+ in the plant cell and transported to the next step of the photosynthesis reaction as NADPH -some ATP is made

6 The Dark Reaction (or Calvin Cycle) is the 2 nd step in PS: -NADPH comes from the Light reaction to the site of dark reaction to “drop off” the hydrogen collected -CO 2 from the air is used to combine with the H and produce a sugar molecule (CH 2 O)n -the NADP+ returns to the light reaction to get another H -ATP is used to provide some energy to make the sugar -If the Calvin Cycle does not happen, no sugar is made Q/TSjL4DyUnhI/AAAAAAAAACs/xg261s8seQM/s1600/calvin_cycle.jpg

7 Just a few notes… -the light reaction must have light to occur…this means plants do not photosynthesize at night -plants must have chlorophyll to photosynthesize…this means that flowers, red, orange and yellow leaves, etc. are not capable of making sugar -the dark reaction can happen in the light…it just does not need light to happen…it only needs the product of the light reaction -so…without light the dark reaction can only happen for a short amount of time before the plant runs out of H and cannot continue to make sugar Application: When hay is harvested, it is always higher in sugar content if harvested after lunch, rather than before. Explain…?

8 How do plants get gasses into and out of the cells for PS? STOMATA (stoma singular)– small openings on the underside of plant leaves that let air pass into and out of the plant. They are controlled by GUARD CELLS that sense atmosphere conditions which may cause water loss and close up the stoma Why do you think the stoma are on the underside of the leaf? Open stomata Closed stomata Guard cells are stretched out Guard Cells are cupped

9 Most plants we are familiar with use Carbon Dioxide directly from The air. These are called C 3 plants. Many are very important in agriculture: soybeans, wheat, oats and rice. In times of drought or extreme heat These plants shut their stomata and then do not make sugar. This in return causes a low yield. Farmers usually grow these under irrigated conditions to insure they get a good crop. How does irrigation help keep the plant photosynthesizing? Why can these plants not make sugar after they shut their stomata? What are the missing ingredients?

10 Some plants have adapted over the years (millions by evolution) to drought…they don’t rely on the C 3 process to make sugar. Instead they use different pathways and ingredients. C 4 plants have an enzyme that can find Carbon Dioxide inside the leaf, even when the stomata are closed. This allows them to continue making sugars even when conditions are hot and dry and minimize water loss. Examples: corn, sorghum, sugar cane…all tropical in origin and important in agriculture. chemistry/files/2010/08/shutterstock57605581.jpg

11 CAM plants can close their stomata during the day and still photosynthesize because they collect their Carbon Dioxide at night and convert it to an acid. They store the acid and then use the carbon molecules the next day for sugar making but don’t have to worry about losing water. CAM stands for Crassulacean Acid Metabolism, the acid that the Carbon is stored in. Most plants in this category are Succulents…they have thick, leaves filled with a juicy tissue such as aloe, cacti and jade. Agave also fits in this category. Do you know what agave is used for?? Do any of these plants have leaves?

12 How does photosynthesis affect the environment?? -many fossil fuels give off Carbon products as they burn -power plants -auto exhaust -fireplaces -factories Autotrophs act as a sink to soak up all the extra Carbon Dioxide in the atmosphere so it doesn’t cause problems. When you plant trees and grass and flowers, you are part of the solution. The lumber industry, urban growth, rainforest destruction all remove autotrophs from the environment. If you take part in or use products of these activities, you are part of the pollution!! Many species are also lost in the destruction. Some of these will never recover and future generations will never see them. In addition, many drugs come from plants. Species destruction may keep us from finding a cure for disease someday.

13 The Greenhouse Effect is a large problem: -rays from the sun reflect off the Earth and into space -pollution in the air keeps many of these rays from reflecting and they reradiate until they can escape -this extra heat from the rays causes an increase in the surface temperature of the Earth, which in turn causes many different environmental problems -CO 2 has increased by about 30% in the atmosphere. This has led to Global Warming: -warming of the Earth’s surface and oceans -causes some species to die out -ice melting at the polar caps -changing weather patterns -increased number of tropical storms and ‘canes -won’t know extent of damage for many years DO SOMETHING GOOD...PLANT A TREE!!!


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