Chapter 3, Section 3

Photosynthesis

Sources of Energy Photosynthesis: the process by which a

cell captures energy in sunlight and uses it to make foodo Photo– means “light”, synthesis– means

“putting together” Nearly all living things obtain energy either

directly or indirectly from the energy of sunlight captured during photosynthesis

Review Autotroph

o an organism that makes their own foodo What are some examples?

Heterotropho an organism that cannot make their own foodo What are some examples?

Fungi– absorb their food from other organisms

The Two Stages of Photosynthesis

1. Capturing the sun’s energy

2. Producing sugars

Both stages must occur in the correct order

Stage 1: Capturing the Sun’s Energy

Energy capturing process occurs mostly in leaves

The green color comes from pigments– colored chemical compounds that absorb light

The MAIN photosynthetic pigment in chloroplasts is called CHLOROPHYLL

Chlorophyll captures light energy and uses it to power the second stageof photosynthesis…

Stage 2: Using Energy to Make Food

Cell uses captured energy to produce sugars

The cell needs two raw materials1. water – enters plant through roots and move upward

to the leaf2. carbon dioxide– enters through openings called

stomata

Once in the leaves the water and carbon dioxide move into the chloroplasts….

Stage 2: Using Energy to Make Food

Inside the chloroplasts undergo a series of chemical reactions

Chemicals are the products of the reactions (2)o Six-carbon sugar (use this energy to carry out cell

functions)o Oxygen (exits leaf through stomata)

Fun Fact: Almost all oxygen in Earth’s atmosphere was produced by living things through the

process of photosynthesis

The Photosynthesis Equation

The arrow stands for YIELDS

Raw Materials Products

What happens to the sugar produced in photosynthesis?

Plants use it for food

Some sugar is made into other compounds, such as cellulose

Some sugar is stored in the plant’s cells for later use