Photosynthesis

Question: Why do leaves change color in the fall?

Why is photosynthesis important?

Photosynthesis is the process in which plants (also called autotrophs or producers) use water and the radiant energy of the sun to create simple sugar (glucose) as a food source with oxygen as one of the products of the reaction.

Why is photosynthesis important? Humans depend on plants for food, and plants use photosynthesis for food. Oxygen is a waste product of photosynthesis, and we breathe oxygen.

Photosynthesis is how plants make food: Glucose 6:12:6 1:2:1

The carbohydrate is called glucose – it is a simple sugar and you are probably very familiar with its taste if you have eaten or drunk any of the products here.

To make glucose, plants take CO2 (Carbon Dioxide from the atmosphere) and H2O (Water, usually from the ground water surrounding the plant)

But… splitting these molecules apart is very difficult But… splitting these molecules apart is very difficult. So to get the oxygen apart from the hydrogen and carbon takes a little something extra…

The Solution?

Sunlight has enough energy that plants can use it to break apart the bonds that hold together the carbon dioxide and water molecules.

Photosynthesis uses 6 CO2 and 6 H2O atoms to make glucose with oxygen as a waste product. (Reactants) (Products)

Where does this reaction take place?

Where does this reaction take place? Chloroplasts!

Chloroplast Structure: Thylakoids: membrane-bound, flattened sacs where light is captures and light reactions occur. Stroma: Fluid matrix that the thylakoid membranes are suspended in. Grana: columns of stacked thylakoids Chlorophyll: green pigment that captures and absorbs all light except the green, which is reflected.

2 Stages of Photosynthesis

2 Stages of Photosynthesis 1. Light-Dependent Reactions Require: Light, Water, Chlorophyll Occurs: Rapidly, non-stop during daylight Location: Thylakoids (flattened sacks embedded with chlorophyll) Products: Oxygen ATP and NADPH (which will be used to energize the second stage)

2. Light Independent Reactions (or Calvin Cycle) Require: Carbon Dioxide, ATP, NADPH Occurs: in the absence of light Location: in the Stroma (surrounding the grana) Products: High Energy Sugars (glucose) ADP and NADP (sent back to Light Reactions to recharge)

Questions: 1. Why is photosynthesis important to humans? 2. Name two reactants in photosynthesis. 3. Name one product of photosynthesis.