Transcript Document
CHAPTER 8 PHOTOSYNTHESIS AUTOTROPHS Can make their food using sunlight Examples: plants and algae Also known as producers HETEROTROPHS Cannot make their own food Examples: animals and fungi Also known as consumers ENERGY AND ATP All organisms get energy by breaking down the chemical compounds in food and making ATP and other compounds ATP (Adenosine Triphosphate) –It is the chief energy-storing molecule Photosynthesis Requires: Light Chlorophyll (found in chloroplasts) Raw materials (carbon dioxide, CO2 (gas that plants take in from the air) & water, H2O (plants take in from their roots)) PHOTOSYNTHESIS Process by which autotrophs convert sunlight into a usable form of energy (glucose) Chemical Equation: 6CO2 (g)+ 6H2O ---sunlight-->C6H12O6 + 6O2(g) Carbon Dioxide (gas) Water Glucose Oxygen (gas) Photosynthesis Video PHOTOSYNTHESIS Takes place in organelles called chloroplasts (found only in plant cells) Grana – stacks of disks that contain chlorophyll Stroma – liquid part PHOTOSYNTHESIS Special pigments are found inside the chloroplasts to absorb light Pigment - a molecule that absorbs certain wavelengths of light and reflects others The reflected wavelengths determine what color you perceive an object to be Pigments of Photosynthesis Chlorophyll – green pigment; acts as light trap 2. Xanthophyll – yellow pigment; passes light to chlorophyll 3. Carotene – orange pigment; passes light to chlorophyll 1. 2 PHASES OF PHOTOSYNTHESIS 1. Light-dependent Stage – Sunlight is absorbed by chlorophyll inside the chloroplast Chlorophyll changes energy from sunlight into ATP Some of the ATP is used to split water into hydrogen & oxygen Oxygen is released from the leaf into the atmosphere 2 PHASES OF PHOTOSYNTHESIS 2. Light-Independent Stage (or Calvin Cycle) ATP (from light dependent stage) and hydrogen (from the water that was split) combines with carbon dioxide (from the atmosphere) The end result is the formation of glucose (sugar) Rate of Photosynthesis Depends on the following things: Light intensity Availability of raw materials Temperature Leaves Stomata are pores or holes in the epidermis of the leaf that allow gas exchange Carbon dioxide comes in through the opening and oxygen leaves through the pore This is important for photosynthesis to occur Leaves cont’d Guard cells on each side of the stomata control its opening and closing Water is also lost through the stomata in a process called transpiration, so plants only leave stomata open long enough to do photosynthesis Picture of Stomata & Guard Cells Label this picture on your paper More Pictures of Stomata Above: Diagram of how stomata open and close http://www.youtube.com/watch?v=At1BJJDcXhk