PhotosynthesisPhotosynthesis

Chapter 3Chapter 3

What’s PhotosynthesisWhat’s Photosynthesis

A process in which cells capture sunlight and A process in which cells capture sunlight and uses it to make food.uses it to make food.

““photo” = lightphoto” = light ““synthesis” = to make or put togethersynthesis” = to make or put together Only occurs in plants, algae, and some bacteriaOnly occurs in plants, algae, and some bacteria

Two Stage Process to Two Stage Process to PhotosynthesisPhotosynthesis

Use energy from sun to convert carbon dioxide Use energy from sun to convert carbon dioxide and water into oxygen and sugars (includes and water into oxygen and sugars (includes glucose).glucose).

First stage: Capturing the sun’s energyFirst stage: Capturing the sun’s energy This stage occurs in the leaves and other green This stage occurs in the leaves and other green

parts of the plant. (Like chloroplasts)parts of the plant. (Like chloroplasts) Chloroplasts give the plant its green color.Chloroplasts give the plant its green color. The green color comes from The green color comes from pigmentspigments, or the , or the

colored chemical compound that absorbs light.colored chemical compound that absorbs light. Main pigment is Main pigment is chlorophyllchlorophyll Chlorophyll captures the light energy and uses Chlorophyll captures the light energy and uses

it to power the 2it to power the 2ndnd stage. stage.

Stage 2: Using energy to make foodStage 2: Using energy to make food Uses the captured energy to produce sugars.Uses the captured energy to produce sugars. Needs water and carbon dioxide (CONeeds water and carbon dioxide (CO22) for this ) for this

stage to happen.stage to happen. Get water from roots and COGet water from roots and CO22 from the air. from the air. Carbon dioxide enters through Carbon dioxide enters through stomatastomata, small , small

openings underneath the leave.openings underneath the leave. Water and COWater and CO22 move into the chloroplasts move into the chloroplasts Water and COWater and CO2 2 undergo a series of chemical undergo a series of chemical

reactions. reactions. Products from this reaction are oxygen & sugars.Products from this reaction are oxygen & sugars.

Photosynthesis EquationPhotosynthesis Equation

Carbon Dioxide + Water Carbon Dioxide + Water → Glucose + Oxygen→ Glucose + Oxygen

↑↑ ↑↑

These are the reactants These are the productsThese are the reactants These are the products

Photosynthesis & LifePhotosynthesis & Life

Plants use some of the sugars for food Plants use some of the sugars for food Some sugars maybe stored for future use.Some sugars maybe stored for future use. When you eat potatoes & carrots you are When you eat potatoes & carrots you are

eating the plant’s stored food.eating the plant’s stored food. Oxygen leaves the leaves & enters into the Oxygen leaves the leaves & enters into the

atmosphere.atmosphere. Nearly all living things obtain energy directly Nearly all living things obtain energy directly

or indirectly from the energy of the sunlight.or indirectly from the energy of the sunlight.