Download CHAPTER 2 – SEC. 1: PHOTOSYNTHESIS

CHAPTER 2 – SEC. 1:
PHOTOSYNTHESIS
I. WHAT IS PHOTOSYNTHESIS?
• Every living organism on this planet needs
energy to function. For example, cells
need energy to make proteins or bring
substances in and out of the cell.
• Most of the energy used to perform life
functions comes directly from the sun.
• Some organisms such as plants capture
the sun’s energy through its light to make
its own food. This is called
PHOTOSYNTHESIS.
II. PHOTOSYNTHESIS IS A TWO–STAGE
PROCESS
• Stage 1 - Plants take sunlight, carbon
dioxide (from the air), and water (through
the plant’s roots) into a plant’s leaf.
• Stage 2 - Once in the leaf, sunlight,
carbon dioxide, and water react to make
food for the plant (which is the glucose
sugar) and a by-product which is released
into the air (oxygen).
Diagram of the two-steps in
Photosynthesis
Stage One - CAPTURING THE
SUN’S ENERGY
• The first stage in photosynthesis is to capture
the sun’s light in the plant organelles called
CHLOROPLASTS.
• Chloroplasts are found in the leaf of a plant.
• The sun’s light is actually absorbed by the
pigments found inside a chloroplast.
• The main pigment doing the light absorption is
CHLOROPHYLL.
• As the sun’s light is
accepted into the
chloroplast, all the
colors of the visible
spectrum are
absorbed except the
color green.
• It is reflected back out
causing you to see
the plant’s color as
green.
Stage 2 - USING ENERGY TO
MAKE FOOD
• In the second stage of photosynthesis, the
captured sunlight reacts with two raw
materials inside the plant: water and
carbon dioxide.
• Water comes from a plant’s roots and
carbon dioxide comes from the air in
through the stomas of the underside of a
leaf.
• A stoma is an opening on the underside of
a leaf that allows in certain air molecules
such as carbon dioxide.
• Once the water and carbon dioxide are in
the plant, they make their way to the inside
of a chloroplast.
• In the chloroplast, they undergone a
chemical reaction with the sun’s light to
make glucose sugars (the plant’s food)
and oxygen (expelled through the stoma
into the air we breathe).
III. THE PHOTOSYNTHESIS
EQUATION
• Light energy
• 6 CO2 + 6 H2O  C6H12O6 + 6 02
•
Carbon dioxide
water
glucose
oxygen
• The raw materials needed for photosynthesis
are carbon dioxide, water, and the sun’s light.
• Their reactions make or yields glucose (sugar)
and oxygen.
Light energy
6 CO2 + 6 H2O  C6H12O6 + 6 02
Carbon dioxide water
glucose oxygen
• The number before a molecule is how
many molecules are involved.
• The subscript number tells you how many
atoms of a certain element are involved.
• The number of atoms must be equal or
balanced on both sides of the equation.
What is the glucose sugar used
for?
• Plants use the glucose sugar for food by
breaking it down for its energy content.
• Plants also use the glucose sugar to make
cell parts such as cellulose.
• Plants can also store glucose sugar for
later use (ex. a potato).
IV. PHOTOSYNTHESIS AND LIFE
• Def. of AUTOTROPH – an organism that
can make its own food such as a plant
• Autotrophs get their energy directly from
the sun.
• Def. of HETEROTROPH – an organism
that cannot make its own food such as
animals
• Heterotrophs get their energy indirectly
through the food they eat such as plants.