chapter 2 – sec. 1: photosynthesis. i. what is photosynthesis? every living organism on this...
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CHAPTER 2 – SEC. 1:
PHOTOSYNTHESIS
I. WHAT IS PHOTOSYNTHESIS?
• Every living organism on this planet needs energy to function. For example, cells need energy to make proteins or bring substances in and out of the cell.
• Most of the energy used to perform life functions comes directly from the sun.
• Some organisms such as plants capture the sun’s energy through its light to make its own food. This is called PHOTOSYNTHESIS.
II. PHOTOSYNTHESIS IS A TWO–STAGE PROCESS
• Stage 1 - Plants take sunlight, carbon dioxide (from the air), and water (through the plant’s roots) into a plant’s leaf.
• Stage 2 - Once in the leaf, sunlight, carbon dioxide, and water react to make food for the plant (which is the glucose sugar) and a by-product which is released into the air (oxygen).
Diagram of the two-steps in Photosynthesis
Stage One - CAPTURING THE SUN’S ENERGY
• The first stage in photosynthesis is to capture the sun’s light in the plant organelles called CHLOROPLASTS.
• Chloroplasts are found in the leaf of a plant.
• The sun’s light is actually absorbed by the pigments found inside a chloroplast.
• The main pigment doing the light absorption is CHLOROPHYLL.
• As the sun’s light is accepted into the chloroplast, all the colors of the visible spectrum are absorbed except the color green.
• It is reflected back out causing you to see the plant’s color as green.
Stage 2 - USING ENERGY TO MAKE FOOD
• In the second stage of photosynthesis, the captured sunlight reacts with two raw materials inside the plant: water and carbon dioxide.
• Water comes from a plant’s roots and carbon dioxide comes from the air in through the stomas of the underside of a leaf.
• A stoma is an opening on the underside of a leaf that allows in certain air molecules such as carbon dioxide.
• Once the water and carbon dioxide are in the plant, they make their way to the inside of a chloroplast.
• In the chloroplast, they undergone a chemical reaction with the sun’s light to make glucose sugars (the plant’s food) and oxygen (expelled through the stoma into the air we breathe).
III. THE PHOTOSYNTHESIS EQUATION
• Light energy• 6 CO2 + 6 H2O C6H12O6 + 6 02• Carbon dioxide water glucose oxygen
• The raw materials needed for photosynthesis are carbon dioxide, water, and the sun’s light.
• Their reactions make or yields glucose (sugar) and oxygen.
Light energy6 CO2 + 6 H2O C6H12O6 + 6 02
Carbon dioxide water glucose oxygen
• The number before a molecule is how many molecules are involved.
• The subscript number tells you how many atoms of a certain element are involved.
• The number of atoms must be equal or balanced on both sides of the equation.
What is the glucose sugar used for?
• Plants use the glucose sugar for food by breaking it down for its energy content.
• Plants also use the glucose sugar to make cell parts such as cellulose.
• Plants can also store glucose sugar for later use (ex. a potato).
IV. PHOTOSYNTHESIS AND LIFE
• Def. of AUTOTROPH – an organism that can make its own food such as a plant
• Autotrophs get their energy directly from the sun.
• Def. of HETEROTROPH – an organism that cannot make its own food such as animals
• Heterotrophs get their energy indirectly through the food they eat such as plants.
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