Notes 4-1 Photosynthesis. Sources of Energy Nearly all living things obtain energy either directly...

Notes 4-1

Photosynthesis

Sources of Energy• Nearly all living things obtain energy either

directly or indirectly from the energy of sunlight captured during photosynthesis.

Autotrophs:• Organisms that

make their own food

• Example: Plants photosynthesize

Heterotrophs:• Organisms that

must consume food (cannot make their own food)

• Example: Animals eat plants or other animals

Photosynthesis

• Process by which a cell captures the sun’s energy and uses it to make food

• Plants convert carbon dioxide and water into oxygen and sugars (food)

• Photosynthesis occurs in 2 steps

Stage 1:

• Chlorophyll (a green pigment inside the organelle called chloroplasts in plant cells) absorbs the sunlight

• This provides the “power” for stage 2 of photosynthesis

*Chlorophyll is what makes the plants green!

Stage 2:• Roots of plants absorb water and it travels up

through the stem to the leaves• Carbon dioxide enters the plants through small

holes on the underside of the leaves called stomata

• Water and carbon dioxide move into the chloroplasts of the plant cells

• In the chloroplasts, a chemical reaction occurs and sugars (carbs) are produced as food for the plants and oxygen is released as a waste product through the stomata (this is the oxygen that we breathe!!)

The Two Stages of Photosynthesis• Let’s look at the 2 stages again, but

with pictures this time!

Photosynthesis Equation

• The left side of the equation shows what the plants are using (6 molecules of CO2 and 6 molecules of H2O)

• The arrow means “yield” or “produces”• The right side of the equation shows the

products, or what the plant is making (1 molecule of sugar and 6 molecules of O2)

Where do plants get the water they need for photosynthesis?

• From the ground, from the rain, etc…• It travels up through their roots, through

the stem and to the leaves

Where do plants get the CO2 they need for photosynthesis?

• When we exhale when we breathe, we release carbon dioxide as a waste product

• Plants take it in through their leaves

What do the plants do with the oxygen?

• The plants do not need the 6 molecules of oxygen, so they release it as a waste product.

• This is the oxygen gas we breathe!

What do the plants do with the sugars?

• The plants use some of the sugars they make as immediate food for themselves

• Whatever they don’t use right away, they store for later

• When we eat plants (fruits and veggies) we are eating their stored energy!

Let’s Review!

• Name an example of an heterotroph.

• What 3 things do plants need in order to photosynthesize?

Any animal or fungus, because they cannot make their own food.

Sunlight, water, and carbon dioxide.

Let’s Review!

• Plants are autotrophic. True or False?

• What happens to the Oxygen gas that plants release during photosynthesis?TRUE, because

they make their own food. We breathe it

in!