Earth Science 5.2 Photosynthesis
Photosynthesis
Objectives
Today, students will. . .
1.
Summarize how energy is captured from
sunlight
2.
Identify three environmental factors
that affect the rate of photosynthesis
Stages of Photosynthesis


Photosynthesis is a
process that provides
energy for almost all
life.
Photosynthesis is the
process by which a plant
makes food for it to grow.
Stages of Photosynthesis
Plants, through photosynthesis:
 take IN water and carbon
dioxide as the raw
ingredients,
 Make food (sugars) with it
using energy from the sun,
 and put OUT oxygen as a
byproduct of the process.
Stages of Photosynthesis

Photosynthesis has three
stages
1.
Energy is captured from
sunlight
2.
Light energy is converted to
chemical energy, which is
temporarily stored in ATP and
NADPH. This powers the
process.
3.
The chemical energy stored in
ATP and NADPH powers the
formation of glucose, using
carbon dioxide and water.
Stages of Photosynthesis

Glucose, a form of sugar,
provides the food that
plants use to survive and
grow.

Glucose is the plant’s food
that allows the plant to
carry on it’s life processes
such as growth and repair!
Summary of Photosynthesis
Photosynthesis requires the
following 4 things:
Carbon Dioxide
2. Water
3. Light Energy from sunlight
4. Chlorophyll
1.
Summary of Photosynthesis
In photosynthesis:


Plants take IN carbon dioxide and
water.
The chlorophyll in the plant’s
leaves uses the light energy from
sunlight to power the process of
converting this to food for the
plant.
Summary of Photosynthesis
In photosynthesis:



Plants convert the carbon dioxide
and water into a form of sugar
called glucose that the plant uses
for food.
This food gives the plant energy
for it’s own life processes.
Plants give OUT oxygen as a
byproduct of this reaction.
Summary of Photosynthesis
Ingredients: Carbon Dioxide


Carbon Dioxide (CO2) is one of the
ingredients that a plant uses to
create glucose.
Carbon dioxide comes from all the
animals on Earth, including us (it's
what we exhale).
Summary of Photosynthesis
Carbon Dioxide:


Carbon Dioxide enters the plant
through small pores on the
bottoms of leaves called stomata.
Carbon dioxide combines with
water to create the glucose sugars
that the plant uses for it’s food.
Summary of Photosynthesis
Ingredients: Water



Water (H2O) is the other
ingredient that is used by all plants
in photosynthesis.
Water is drawn up into the plant
through the roots, up the stem and
into the leaves where
photosynthesis occurs.
The water interacts with carbon
dioxide (CO2) to create the plant’s
food, a sugar called glucose.
Summary of Photosynthesis
Sunlight: Energy is
Captured


Sunlight is the main ingredient
that powers the process.
Sunlight is where the energy
comes from originally to convert
the water and carbon dioxide
into sucrose 5-carbon sugars.
Summary of Photosynthesis
Sunlight: Energy is Captured


Plants trap sunlight energy with
chloroplasts and use the energy
to power the process of
photosynthesis.
Chloroplasts are found within the
cells of all plants, giving the
leaves of plants their green
color.
Summary of Photosynthesis
Chlorophyll:


Chlorophyll is the chemical in
chloroplasts that reacts to
sunlight.
Chloroplasts are inside the cells
of all plants.
Plant cell
Chloroplasts in plant cell
Summary of Photosynthesis
Chlorophyll:

The chlorophyll in plants catches
the sunlight energy and uses it to
charge ATP, like charging a
battery.
Plant cell

Once charged, the energy in the
ATP can be released later to
power the process of converting
the CO2 and H2O into glucose.
Chloroplasts in plant cell
Summary of Process Photosynthesis
Step 1: Absorption of
Light Energy
Energy is captured from sunlight
by chloroplasts: Inside chloroplasts
are disc-shaped thylakoids.

When sunlight strikes thylakoids,
light energy is transferred to
electrons in the chlorophyll.

These electrons “become excited”
and jump from thylakoid to thylakoid
in “electron transfer chains”.

Summary of Photosynthesis
Step 2: Splitting of Water
(H20) and Creation of
Oxygen (O2)


Electrons that leave these
chlorophyll molecules get replaced
by electrons from water molecules
that are disassembled (taken apart).
The particles left from the
disassembled water molecules
combine to form oxygen molecules
which are than given off by the
leaves as a byproduct.
Summary of Photosynthesis
Step 3: Creation ATP
through Electron
Transfer Chains


Electrons that leave the
chlorophyll and move through
these “electron transfer chains”
catalyze a chemical reaction that
results in the creation of both
ATP and NADPH.
ATP and NADPH both function
like batteries; they can take and
hold energy and than release it
later when needed to catalyze a
process that needs activation
energy.
Summary of Photosynthesis
Step 4: Carbon Dioxide
Fixation



Plants take in carbon dioxide from
the atmosphere through pores in
their leaves called stomata.
Carbon molecules from this carbon
dioxide are used to create organic
compounds (sucrose-sugars) in a
process called “The Calvin Cycle”.
Through Carbon Dioxide Fixation in
The Calvin Cycle, carbon dioxide
(CO2) is used to make a five-carbon
sugar called glucose that plants use
to grow and repair themselves.
Summary of Photosynthesis
Step 4: Calvin Cycle
In the Calvin Cycle
1.
2.
ATP adds phosphate groups and
NADPH adds electrons which
transform these 3-carbon
compounds.
3.
One of these two 3-carbon
molecules transforms into glucose;
food for the plant’s life processes.
4.
The other 3-carbon molecule goes
back into the process and
starts the cycle over again so
more sucrose can be produced.
5.
5
1 molecule of carbon dioxide gets
added to a 5-carbon compound by
an enzyme. Two 3-carbon
molecules result from this.
1
4
2
3
Summary of Photosynthesis
Summary of Whole Process: Look at
the diagram at right.



In the top section, sunlight
provides power for the reaction in
the electron transport chain that
takes water in (H2O) and puts out
oxygen (O2) as a byproduct.
In this first stage, ATP and
NADPH are created. Like charged
batteries, they hold energy to
release in the next step of the
process.
In the bottom section, the Calvin
Cycle takes in molecules of carbon
(from CO2) and ATP and NADPH
both catalyze a reaction that
produces sugar in the form of
glucose.
Summary of Photosynthesis
4 factors that affect photosynthesis:




Light: The more sunlight a plant gets, the
faster photosynthesis will happen.
Water: Plants require water for
photosynthesis. If there is not enough
water, photosynthesis slows down or stops.
Temperature: Temperature range affects
photosynthesis. Too high or too low a
temperature will slow down or stop the
enzymes that help make parts of the
process happen.
CO2: The amount of Carbon Dioxide (CO2)
available affects photosynthesis. The more
CO2 available, the faster photosynthesis
will occur.
Section Review

Key Concepts. . . .
 Photosynthesis has three stages
○ First energy is captured from sunlight
○ Two, energy is temporarily stored in ATP and NADPH
○ Third, organic compounds are made using ATP, NADPH, and Carbon Dioxide
 Pigments absorb light energy during photosynthesis.
 Electrons excited by light, travel through electron transport chains, in
which ATP and NADPH are produced.
 Through carbon dioxide fixation, by the Calvin Cycle, carbon dioxide in
the atmosphere is used to make organic compounds (glucose), which
store energy and provide the plant with food.
 Photosynthesis is directly affected by environmental factors such as the
○ intensity of light,
○ availability of water,
○ the concentration of carbon dioxide,
○ and temperature range.