Photosynthesis – what you really need to know…

Warm Up #1 1.Give an example of an autotroph. 2.List 2 examples of a heterotroph. 3.Where is the energy stored in an ATP molecule? 4.What’s wrong with ATP’s energy storing capabilities?

Warm Up #2 1.Write the chemical equation for photosynthesis. 2.What are the reactants? 3.What are the products? 4.Where do the reactants come from? 5. What is the pigment found in plants that give them their green color?

Warm Up #3 1.Name the two cycles of photosynthesis. 2.Is light required for the light reactions? 3.Is light required for the Calvin Cycle? 4.Can the Calvin cycle work if light is present? 5.What is required for photosynthesis to take place?

Energy and Life Autotroph – organisms that are able to make their own food (plants) Heterotroph – organisms that must obtain energy from food they consume.

Energy and Living Things: Energy in Living Systems Energy flows through living systems. Energy flows from autotrophs ( organisms that make their own food) to heterotrophs (organisms that rely on others for food).

ATP The ultimate source of all energy is the sun. Energy is stored in cells in the mitochondria in the form of ATP (adenosine triphosphate) Has three phosphates – the key to it’s ability to store and release energy lies in the bonds between the phosphates. Energy stored in the cell is released gradually in a series of enzyme (protein) assisted reactions. Energy is stored temporarily in molecules of ATP. Released energy is enough to process most of the cell’s activities.

Storing and Releasing Energy ADP Adenosine diphosphate – looks like ATP but only has 2 phosphates This small difference is the key to the energy storing capabilities – ADP adds a phosphate and becomes ATP ( a fully charged battery) Energy is released when the bonds between the phosphates are broken

PHOTOSYNTHESIS Literally means “put together with light” Process by which light energy (energy from the sun) is converted into chemical energy (energy we need to survive). Almost all autotrophs, especially plants are photosynthetic organisms.

EQUATION 6CO 2 + 6H 2 O C 6 H 12 O 6 +6O 2 Reactants Products Carbon Dioxide Glucose (sugar-starch) Comes from the atmosphere from respiration Into the leaves through the stomata Water Oxygen Comes from the soil by osmosis Light

Requirements for Photosynthesis In order for photosynthesis to occur 4 things must be present: 1. Carbon Dioxide 2. Water 3. Light 4. Chlorophyll – plants principal pigment – gives it a green color. Light is a form of energy – any compound that absorbs light – stores energy

Factors affecting photosynthesis… Temperature – not as much photosynthesis in the winter months because the temperature drops. Intensity of Light – the more intense the light the more photosynthesis and vice versa

Why do leaves change color in the fall? During winter, there is not enough light or water for photosynthesis. The trees will rest, and live off the food they stored during the summer. They begin to shut down their food-making factories. The green chlorophyll disappears from the leaves. As the bright green fades away, we begin to see yellow and orange colors. Small amounts of these colors have been in the leaves all along. We just can't see them in the summer, because they are covered up by the green chlorophyll. The bright reds and purples we see in leaves are made mostly in the fall. In some trees, like maples, glucose is trapped in the leaves after photosynthesis stops. Sunlight and the cool nights of autumn cause the leaves turn this glucose into a red color. The brown color of trees like oaks is made from wastes left in the leaves.

Steps of Photosynthesis

Summary of the light reactions Occurs in thylakoids Needs light and water Produces oxygen, ATP and NADPH Electrons become excited by sunlight and pass down the ETC using NADPH Water is split (photolysis) into H+ ions and oxygen and high energy e-’s

Summary of the Calvin Cycle Occurs in the stroma Uses NADPH and ATP from the light reaction and carbon dioxide from the atmosphere Series of reactions lead to the production of glucose, NADP+ and ADP + P

6CO 2 + 6H 2 O C 6 H 12 O 6 +6O 2 For the reactants write the compounds name and how it gets into photosynthesis EXAMPLE - 6CO 2 – carbon dioxide, enters the leaf through the stomata from the atmosphere For the products write each compound name and how it is used by hetertrophs

Page 217(page 26 in notebook) Answer #1, 2,4,5, 6, 7, 10, 11, 12, 16