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Cellular Energy and Photosynthesis
Living Things use Energy
Energy is the ability to do work
Cells use chemical energy to do work.
– Cell growth
– Reproduction
– Active transport
– Movement
– Chemical reactions
Sun is our energy source.
• Energy enters most ecosystems as
sunlight and leaves as heat.
• Photosynthesis: a chemical reaction that
converts solar energy into the chemical
energy stored in the bonds of organic
molecules (food)
• One important product of photosynthesis is
glucose
ATP and Energy
Cellular Respiration is the chemical
reaction that breaks down glucose and
uses the energy to make ATP.
– Glucose is made during Photosynthesis.
ATP is the basic energy source used by all
types of cells.
ATP
ATP = adenosine triphosphate.
This is the compound that directlysupplies the energy to do cellular work.
How ATP Works
The release of one of the phosphate groups makes energy available to do cellular work.
ATP energizes other molecules by transferring one phosphate group.
Autotrophs & Heterotrophs
Autotrophs: organisms able to use light energy from the sun to make their own food.
Examples: plants, algae, and some bacteria.
Heterotrophs: organisms that obtain food by consuming other living things.
Examples: fungi, animals
Both autotrophs & heterotrophs must convert the energy that is stored in the bonds of their food into ATP.
What is Photosynthesis?
The process of photosynthesis is a chemical
reaction
It is the most important chemical reaction on our
planet!!
Life on Earth is made possible by the SUN and
PHOTOSYNTHESIS
What organisms can do photosynthesis?
Light and Pigment
Light is the form of energy that comes from the
sun
Pigment: light absorbing molecules which allow
plants to gather light energy from the sun
absorbs some wavelengths of light but reflects others
to produce color
Pigment: Chlorophyll
Two types: Chlorophyll a and chlorophyll b
Plants are green because the green wavelength is
reflected, not absorbed.
Chlorophyll Absorption Spectrum
Chlorophyll absorbs blue-violet
& red light best
Chloroplasts
Photosynthesis occurs
in plant organelles called
chloroplasts
Describe Photosynthesis
Method of converting
sun energy into
chemical energy usable
by cells
Uses sunlight to
convert H2O and CO2
into sugars and O2
Energy is stored as
sugar
Plants need light
energy, CO2, and H2O
Photosynthesis Reactions
(requires energy,
like driving a car.
Fuel = light)
Why do we need Plants and Other Photosynthetic organisms?
Without Photosynthetic organisms, we’d suffocate : WHY?
– The oxygen released during photosynthesis is necessary for all living things.
Without photosynthetic organisms, we’d starve : WHY?
– We cannot make our own food (glucose, energy), we must get our food from plants.
– Plants are the first step in the food chain.
So: Animals and plants are interdependent
Energy and Matter in Ecosystems