4.1 Photosynthesis

7.1.d Students know that mitochondria liberate energy for the work that cells do and that chloroplasts capture sunlight energy for photosynthesis.

Sources of Energy• ALL cells need energy!• Photosynthesis- process by

which a cell captures energy in sunlight and uses it to make food

• Key Concept: “Nearly all living things obtain energy either directly or indirectly from the energy of sunlight captured during photosynthesis."

• Autotroph- organism that makes its own food

• Heterotroph- organism that cannot make its own food

Sources of Energy

The Two Stages of Photosynthesis

Key Concept: “During photosynthesis, plants and some other organisms use energy from the sun to convert carbon dioxide and water into oxygen and sugars.”

Oxygen exits through the stomata on the underside of the leaf.

Carbon dioxide enters the leaf through openings called stomata

Water inters the plant through roots and moves upward to the leaves

Stage 2The captured light energy is used to produce sugars and oxygen from water and carbon dioxide.

Sugar produced are used by the plant cells for energy

The Two Stages of Photosynthesis• Photosynthesis takes place in 2 stages: capturing

sunlight and producing sugar• Pigments- colored chemical compounds that absorb

light• Chlorophyll- main photosynthetic pigment in

chloroplasts• Chloroplasts- are the green organelles in plant cells

that give the plant its color• Chlorophyll is like solar “cells” or cells that capture the

energy in light in a calculator• The captured light is used to power the second stage

The Two Stages of Photosynthesis• 2 raw materials needed for stage 2 are water and carbon

dioxide• Roots absorb water, water then moves up through stem to the

leaves, carbon dioxide enters through the stomata• Once the water and carbon dioxide are in the leaf they move

into the chloroplasts• Stomata- small openings on the underside of leaves• In the chloroplasts the water and carbon dioxide go through

chemical reactions• These chemical reactions are powered by the energy

captured in stage 1• One important byproduct of this chemical reaction in oxygen

and exits through the stomata

The Two Stages of Photosynthesis• The Photosynthesis equation:

6CO2 + 6H2O   → C6H12O6 + 6O2

Carbon Dioxide

Oxygen

Water

SugarLight energy

The Photosynthesis Process Activity

• Click the Active Art button to open a browser window and access Active Art about the photosynthesis

process.

How does the sun supply living things with the energy they need?What happens during the process of photosynthesis?

Review