Download Photosynthesis

NAME ________________________
PHOTOSYNTHESIS
WILBERT
DATE ___________
7 _____
PHOTO
(Greek “light”)
SYNTHESIS (Greek “putting together”)
PHOTOSYNTHESIS IS THE PROCESS THAT ALLOWS PLANTS
TO CAPTURE LIGHT ENERGY AND CHANGE IT INTO CHEMICAL (FOOD)
ENERGY.
THE PROCESS
Photosynthesis takes place in plant cells that have structures called
chloroplasts. FOOD MAKING HAPPENS IN THESE CELL STRUCTURES.
(A single plant cell can have 20-100 chloroplasts.)
Inside the chloroplasts are molecules that capture the energy in sunlight. These
molecules are called pigments. The main pigment in chloroplasts is
chlorophyll (which is green).
The captured energy from the sun gets photosynthesis started. Water, from the
soil, is absorbed by the roots. It is transported to the leaves and into the
chloroplasts. Carbon dioxide, a gas from the air, enters the plant leaves
through microscopic openings. The carbon dioxide will find its way into the
chloroplasts.
Inside the chloroplasts the water and carbon dioxide molecules are used to make
food. Making food is powered by solar energy. As a result, a sugar called
glucose is made. Glucose is the name of the food that plants make. About
50% of the glucose is used by the plant for its own energy supply. The rest is
changed into other molecules for building things such as wood, leaves, stems,
roots, flowers, seeds, fruits, etc.
When water molecules are taken apart to make food, the oxygen in H2O is
released into the air through microscopic openings in the leaves. A little water
vapor (H2O in the gas state) is also released into the air, too.
SUMMARIZING PHOTOSYNTHESIS
WITH A CHEMICAL EQUATION
6CO2 + 6H2O
carbon
dioxide
water
+ Light Energy
light captured
by chlorophyll
C6H12O6
makes
sugar called
glucose
+
6O2
oxygen gas
released
Explanation: The light energy absorbed by chlorophyll is used to break water (H 2O) down into
hydrogen and oxygen. The hydrogen is the combined with carbon dioxide (CO 2)
from the air to make a sugar called glucose (C6H12O6). The oxygen that is split
off from the water molecule and one from carbon dioxide can be used directly by
the plant or released into the atmosphere.
The little numbers are called subscripts and tell you how many atoms of each
element are needed. The large numbers are called coefficients. They tell you
how many of each molecule is needed to BALANCE the equation. These means
the total number of atoms should be equal on each side of the arrow.
THE IMPORTANCE OF PHOTOSYNTHESIS
FOOD FOR OTHERS
Plants are important because they are the key organisms, on our planet,
that can capture sun energy and change it into food energy. Nearly all living
organisms get energy either directly or indirectly from energy captured during
photosynthesis. For example, animals cannot make their own food. To get their
energy supply (food) they must eat plants directly or eat other animals which
have eaten plants directly or indirectly.
OXYGEN MAKERS
Photosynthesis is also essential for the oxygen you breathe. Most living
things need oxygen to survive. About 21% of Earth’s atmosphere is oxygen—
thanks to plants and other organisms that carry out photosynthesis (some
bacteria and protists). Please understand that plants need some oxygen to carry
out their life activities.