Transcript Chapter 9 the need for energy

The Need for Energy
Chapter 9
Cell Energy
• All living organisms must be able to obtain
energy from the environment in which they live.
• Plants and other green organisms are able to
trap the light energy in sunlight and store it in the
bonds of certain molecules for later use.
• Other organisms cannot use sunlight directly.
• They eat green plants. In that way, they obtain
the energy stored in plants.
Work and the need for energy
• Active transport, cell division, movement of flagella or
cilia, and the production, transport, and storage of
proteins are some examples of cell processes that
require energy.
• There is a molecule in your cells that is a quick source of
energy for any organelle in the cell that needs it.
• The name of this energy molecule is adenosine
triphosphate or ATP for short.
• ATP is composed of an adenosine molecule with three
phosphate groups attached.
Forming and Breaking Down ATP
• The charged phosphate groups act like the positive poles of two
magnets.
• Bonding three phosphate groups to form adenosine triphosphate
requires considerable energy.
• When only one phosphate group bonds, a small amount of energy is
required and the chemical bond does not store much energy. This
molecule is called adenosine monophosphate (AMP).
• When a second phosphate group is added, more energy is required
to force the two groups together. This molecule is called adenosine
diphosphate, or ADP.
• An even greater amount of energy is required to force a third
charged phosphate group close enough to the other two to form a
bond. When this bond is broken, energy is released.
Forming and Breaking Down ATP
• The energy of ATP becomes available to a cell
when the molecule is broken down.
Adenosine
P
P
P
Adenosine triphosphate (ATP)
P
P
Adenosine diphosphate (ADP)
How cells tap into the energy stored in
ATP
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When ATP is broken down and the
energy is released, the energy must be
captured and used efficiently by cells.
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Many proteins have a specific site
where ATP can bind.
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Then, when the phosphate bond is
broken and the energy released, the
cell can use the energy for activities
such as making a protein or
transporting molecules through the
plasma membrane.
When ATP has been broken down to
ADP, the ADP is released from the
binding site in the protein and the
binding site may then be filled by
another ATP molecule.
ATP
Protein
P
ADP
ADP
Section 9.2
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Of all the organisms in the natural world, green plants are the only ones that
manufacture their own food. This process is called photosynthesis and begins when
light strikes the plant's leaves (both sunlight and artificial light can power this
process). Cells in the plant's leaves, called chloroplasts , contain a green pigment
called chlorophyll which interacts with sunlight to split the water in the plant into its
basic components. Carbon dioxide enters the leaf through holes called stomata and
combines with the stored energy in the chloroplasts through a chemical reaction to
produce a simple sugar. The sugar is then transported through tubes in the leaf to the
roots, stems and fruits of the plants. Some of the sugar is used immediately by the
plant for energy; some is stored as starch; and some is built into a more complex
substance, like plant tissue or cellulose. Fortunately for us, plants often produce more
food than they need, which they store in stems, roots, seeds or fruit. We can obtain
this energy directly by eating the plant itself or its products, like carrots, rice or
potatoes. Photosynthesis is the first step in the food chain which connects all living
things. Every creature on earth depends to some degree on green plants. The
oxygen that is released by the process of photosynthesis is an essential exchange for
all living things. Forests have been called the "lungs of the earth" because animals
inhale oxygen and exhale carbon dioxide in the process of breathing, and plants take
in carbon dioxide and give off oxygen in the process of photosynthesis. But every
year, over 28 million acres of tropical forest are cut and then burned to clear land for
farming. Deforestation is also blamed for the "greenhouse effect" (global warming)
which results from the build-up of carbon dioxide and other gases.
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Activity
Without enough sunlight, plants cannot use the process of photosynthesis
to produce food. Materials:
Small shrub, tree or house plant
Cardboard or aluminum foil
Scissors
Paper clips
1. Pick a shrub, tree or houseplant that you can use for an experiment. 2.
Using the cardboard or aluminum foil, cut out some geometrical shapes like
a circle, square or triangle. Make sure your shapes are big enough to make
a patch that will cover nearly half of the plant leaf. 3. Paperclip each shape
on a different leaf. 4. If you use a house plant, place it near a south, west or
east window were it will get plenty of sunlight. Make notes about the
weather each day and add them to your observations. 5. After four days,
remove the shapes from the leaves and observe each of the leaves that had
a shape covering it. 6. Compare the areas on the leaf that were covered
with the shape to other parts of the leaf.
• It is the year 2040 and you are a research
scientist.
The amount of sunlight that reaches the
earth has been reduced because of some
major event like pollution, volcanoes or
global fires.
Farmers are asking you for help to save
their failing crops.
Figure out ways that you might help.