Download Photosynthesis Synthesizing food from light

Photosynthesis
Synthesizing food
from light
7.5A recognize that radiant energy from the Sun is transformed
into chemical energy through the process of photosynthesis
Consider a Hamburger…..
It contains meat that was once a part of a
cow. Where did the cow get the energy to
make the muscle that became meat? A
cow must take in food, such as plants,
that already contain chemical energy. So
where do plants get this energy?
The sun – through the
process of
photosynthesis!
Let’s go over a few terms
 Energy – is the ability to do work
 Forms of energy – potential and kinetic
 Tell me what you know about potential
and kinetic energy
Kinetic and Potential Energy
 Potential Energy is stored
energy.
 Kinetic Energy is the energy
of motion.
Potential Energy
Stored energy due to an object's
position or chemical composition
Kinetic Energy
Energy in motion.
Energy changes  As energy travels through the universe, it
changes from one type or form to
another.
 This is known as “energy transformation”
 Lets take a look at the types.
Energy Transformation
 Energy Transformation is: The
change of energy from one form to
another.
 Example:
Types of energy we will
focus on:
 Of all of the forms or types of energy that
exist, we will focus on just three:
 Chemical energy, mechanical energy and
light (radiant) energy
Chemical Energy
 Energy STORED in matter because of its
CHEMICAL bonds. It is released during
a chemical reaction.
 Examples:
 Battery
 Digestion
 Burning Wood/Fuel
Chemical Energy
 Chemical Energy is required to bond
atoms together.
 And when bonds are broken, energy
is released.
Chemical Energy
 Fuel and food
are forms of
stored chemical
energy.
Mechanical Energy
 Energy that an object has because of its
movement or position.
 Examples:

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Moving Cars
Waterfalls
Running
Sound
Radiant or light Energy
• Type of energy from the sun. Energy
carried by ELECTROMAGNETIC
RADIATION.
• Radiant=LIGHT (but it
Isn’t always visible)
• Examples:
– Visible Light/Sunlight (What you see)
– X-Rays (invisible)
– Microwaves (invisible)
– UV Light (invisible)
Law of Conservation of
Energy
 The law states: Energy cannot be created nor
destroyed.
 What does this mean? It means that energy
can only change its form from one type to
another.
 The energy of the world is a constant because
the total amount of the energy does not
change.
Law of Conservation of
Energy
 For example: Let’s look at a flashlight. It runs on
batteries. The battery has chemical energy.
When the flashlight is turned on, the chemical
energy is first transformed into electrical energy
and then into light energy.
Law of Conservation of
Energy
 Another example: Sunlight absorbed by plants.
This radiant or light energy is converted into
food (chemical energy) by the plant going
through photosynthesis.
Photosynthesis
‘photo’ = LIGHT
‘synthesis’ = BUILD
Photosynthesis means building with Light
 The process through which
plants make their own food
through a chemical change.
What are chemical changes
and chemical reactions?
 Chemical change is when you start with
one molecule and turn it into another.
 Chemical reaction is: when two or more
molecules interact and the molecules
change. Bonds between atoms are
broken and created to form new
molecules.
Chemical reaction ex:
The Chemical change
 A chemical reaction takes place in
plants in which light energy is
converted to chemical energy in the
form of food
 Food = Carbohydrates are used by
all living things as fuel for energy.
• It is the means by which the energy in sunlight
becomes usable to living things.
So…Where does
photosynthesis occur?
 Photosynthesis occurs in the
leaves of a plant.
 Inside the leaf – lots of cells!
Parts of a plant cell
 Chloroplast –
 Mitochondria –
 Stomata -
Close up of plant cell:
 The chloroplast – the chloroplast has
chlorophyll in it (the chemical that makes
plants green). Chlorophyll allows the plant
to absorb radiant energy or sunlight.
Close up of plant cell:
 The mitochondria – the organelle that
generates (make) the energy in the cell
Close up of plant cell:
 The stomata – this is the cell part that
releases the waste oxygen and takes in
carbon dioxide.
All of these
parts work
together to
capture
sunlight and
to convert
this radiant
energy into
chemical
energy or
glucose
(sugar).
The Chemical Reaction Explained
(what happens at the molecular level):
Sunlight provides the energy needed by
chlorophyll to change molecules of
carbon dioxide and water into glucose.
Oxygen is released in this reaction.
What do all of these letters and numbers mean?
Elemental or atomic
symbol reminder!
 If you don’t know what these symbols
are, you need to spend some time
studying the periodic table!
 C=
Carbon
Oxygen
 O=
Hydrogen
 H=
 These elements constantly recombine to
form molecules.
“Reading” a chemical
molecule:
Let’s take a closer
look…
Make a small T chart:
 Reactants
 Products
Some simple steps to
understand chemical formula
terms
 Reactants – what
goes in to the
chemical reaction
(the first part)
 Products – what is
made after the
chemical reaction
occurs (the
second part)
six molecules of carbon dioxide plus six
molecules of water produce one molecule of
sugar plus six molecules of oxygen
Reactants
Energy
(sunlight)
Products
Radiant
Energy
6CO2 + 6H2O 
From
the air
Water
taken up
by roots
Write the formula down!
C6H12O6 + 6O2
Glucose
Energy
Fuel
Oxygen
Note how each of the raw
materials (reactants) end up in
the chloroplasts so that the
whole photosynthesis process
can happen.
Pay attention to what
happens to the products
of photosynthesis.
What about oxygen?
 If you noticed before, oxygen is released
as a product that is NOT used by the
plant.
 This is known as a “by-product or waste”
 Who does use oxygen?
Earth Guide
What do plants do with
the energy?
 As a result of
photosynthesis, plants
meet their immediate
need for energy—to
grow, develop, respond,
and reproduce.
 The food not used right
away is stored by plants
in their roots, stems,
leaves, fruit, or flowers
The glucose is very useful for the plant
Can be
converted into
fats and oils for
the seeds
Can be joined
together to
make cellulose
for the cell
walls
Can be converted
to fructose for
the fruit
Can be used
in
respiration
to release
energy
glucose
can be joined
together to
make starch for
storage
Can be combined
with nutrients from
the soil to make
proteins for the new
The Importance of Plants
 Photosynthesis in plants and a few bacteria is
responsible for feeding nearly all life on Earth.
 It does this by taking energy from the sun and
converting it into a storable form, usually
glucose, which plants use for their own life
processes.
 Animals that consume plants also make use of
this energy, as do those that consume those
that consume plants, and so on to the top of
the food chain.
Our Part
 As important a job as
making all of the world's
food is, there's another vital function that
photosynthesis performs:
 It generates the oxygen that oxygenbreathing animals need to survive. But
here we animals repay the favor. We
exhale the carbon dioxide that plants
need for photosynthesis.
Respiration (not the
breathing kind)
 Cellular respiration is the process in
which nutrients are converted in useful
energy in the cell.
 This “useful energy” is known as sugar.
 Different organisms make different types
of sugars
 Some examples are glucose and fructose
Cellular Respiration
Animals like us need energy which is obtained
from sugars.
This process of obtaining energy from sugar is
known as respiration. Respiration occurs in
the mitochondria of cells.
So now that the plant has made the sugar
energy, it needs to use it. But how does it
do this?
Photosynthesis and Respiration
are reverse operations!
 Photosynthesis: making the energy
 Respiration: using the energy
Comparison
Photosynthesis
Respiration
Food is formed (made)
Food broken down (used)
Energy from the sun stored in
glucose
Energy stored in organic molecules
is released
Carbon dioxide taken in
Carbon dioxide given off
Oxygen given off
Oxygen taken in
Goes on only in light
Goes on day and night
Occurs in presence of chlorophyll
Occurs in all living cells
Illuminating
Photosynthesis
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