Ch. 4.2

Photosynthesis

I. The Nature of Light

• A. The Sun is the source of energy on Earth.• 1. The light you see is white light.• 2. Light passing through a prism appears: red, orange, yellow, green, blue and violet as the visible spectrum.

B. When Light Strikes Objects

• 1. Transmission is when transparent materials allow light to pass through.

• 2. When light hits a shiny surface and light bounces back it’s called reflection.

• 3. Absorption is when dark objects take in light.

• 4. Most objects reflect some colors of the visible light spectrum while they absorb other colors.

Visible Light Spectrum

C. Plants and Light

• 1. Plants absorb some colors of the visible spectrum and reflect others.

• 2. When light strikes the green leaves of a plant, most of the green part of the spectrum is reflected.

• 3. Most of the other colors are absorbed.

Reflect, Absorb, Transmit

D. Plant Pigments

• 1. When light strikes a leaf, it is absorbed by the pigments found in the leaf’s cells.

• 2. Chlorophyll is the most abundant pigment in leaves.

• 3. Chlorophyll absorbs blue and red light and reflects green light.

• 4. Accessory pigments are also found in plants include orange and yellow pigments.

• 5. Most accessory pigments are hidden by the chlorophyll.

Plant Pigments

II. The Photosynthesis Process

• A. Part 1 of Photosynthesis the Plant captures Energy from the Sun.

• B. Part 2 of Photosynthesis the Plant uses that energy to produce food.

C. Capturing Energy

• 1. A substance that absorbs light absorbs energy.

• 2. Photosynthesis begins when light strikes the chlorophyll in a plant’s chloroplasts. This light energy powers the

next stage.

D. The Chemistry of Photosynthesis

• 1. Plants use Carbon dioxide gas and Water as raw materials for photosynthesis.

• 2. During this stage of photosynthesis, Plants use the energy absorbed by chlorophyll to power a series of complex chemical reactions.

• 3. Plants produce Sugar and Oxygen gas.

E. The Photosynthesis Equation

• Carbon Dioxide + Water --- Sugar + Oxygen

• CO2 H2O C6H12O6 O2