Download File Photosynthesis 9

Photosynthesis
7th grade science
All cells need energy to carry out
their functions, such as making
proteins and transporting substances
into and out of the cell
www.kidslu.com/science/mitoch
ondria.php
Plants and other organisms such as
algae and some bacteria, use energy
in sunlight to make their own food
Photosynthesis – the process by
which a cell captures energy in
sunlight and uses it to make food
Nearly all living things obtain
energy either directly or indirectly
from the energy of sunlight
captured during photosynthesis
http://citruscollege.com/apps/pub.asp?Q=847
Grass obtains energy directly from the sunlight because it makes its
own food through photosynthesis. Then the zebra eats the grass; it
gets energy that has been stored in the grass. Lastly, the lion gets
energy that has been stored in the zebra – the zebra and lion obtain
the sun’s energy indirectly
An organism that can make its own food is called an autotroph and
an organism that cannot manufacture its own food is called a
heterotroph
http://creationwiki.org/File:Chemosynthesis.jpg
The Two Stages of Photosynthesis!
During photosynthesis, plants and some other organisms use energy
from the sun to convert carbon dioxide and water into oxygen and
sugars
http://www.emaki.net/blog/2007/03/photosynthesis.html
Stage 1: Capturing the Sun’s Energy
This process occurs mostly in the leaves – the green color comes from
the pigments, which are colored chemical compounds that absorb
light (chloroplasts are the green organelle inside plant cells)
The main photosynthetic pigment in chloroplasts is chlorophyll!
Stage 2: Using Energy
to Make Food
Next, the cell uses the
captured energy to
produce sugars - the cell
needs two raw materials
for this stage – Water
(H2O) & Carbon
Dioxide (CO2)
1. The root absorbs water from the soil
2. Then the water moves up through the plant’s stem to the leaves
3. Carbon Dioxide enters the plant through the small openings on
the underside of the leaves called the stomata
4. Once in the leaves, the water and carbon dioxide move into the
chloroplasts
www.windowtothe
garden.com/thepla
nt.html
Inside the chloroplasts, the H2O and CO2 undergo a complex
series of chemical reactions – the rxns are powered by the energy
captured in the first stage!!
H2O + CO2 
……………….
sunlight
…… 
O2 + C6H12O6
Oxygen (O2) and Six-carbon sugars (C6H12O6) are produced!
Almost ALL of the oxygen in the Earth’s air was produced
by living things through the process of photosynthesis!
6 CO2 +
Carbon Dioxide
Reactants
Light Energy
6 H2O ---> C6H12O6
+
Water
A Sugar
products
6 O2
Oxygen
Six molecules of carbon dioxide and six molecules of water, when
“powered by sunlight” yield a molecule of sugar (sometimes called
starch or glucose) and six molecules of the element oxygen.
A look at things to come…….