Photosynthesis Notes
A crucial endothermic reaction for all life
Prior Knowledge:
1. How do plants obtain food?
2. What is an endothermic
reaction?
3. Why is photosynthesis an
endothermic reaction?
Remember: Endothermic Reactions
● it takes more energy to break bonds in the reactants than is released
when new bonds form in the products.
● The word "endothermic" literally means "taking in heat."
● A constant input of energy, often in the form of heat/light, is needed in an
endothermic reaction.
● In many endothermic reactions, heat is absorbed from the surroundings.
As a result, the temperature drops.
●
The general equation for an endothermic reaction is:
Reactants+Energy→Products
How does this relate to Photosynthesis?
Explain in your own
words what goes into
and what comes out of
photosynthesis
Explain in your own
words why this process
is endothermic.
Photosynthesis in the
most basic definition...
The Endothermic
Reaction
Photosynthesis is a
CHEMICAL REACTION
A chemical reaction is a process that leads to the
transformation of one set of chemical substances to another.
6CO2 + 6H2O + light
REACTANTS
→
C6H12O6 + 6O2
PRODUCTS
The carbon dioxide and water molecules are being broken up
and rearranged into glucose!
More than just Water, Carbon
Dioxide and Light are needed!
Plants need
Chloroplast
Chloroplast are the
location of
photosynthesis.
Two important parts:
-stroma: open space
-stacks (granum) of
thylakoids
Each chloroplast
also contains the
pigment cholorphyll.
What is Chlorophyll
and Why is it
important?
The purpose of
chlorophyll is
to absorb light
energy.
Why are plants green...sometimes?
...a side note
Write this in your own words when your teacher is done explaining
Have you ever noticed that the
leaves on trees turn different colors
in the fall?
Why does this happen?
Plant cells contain pigments.
During the spring and summer, the
most common pigment is
chlorophyll.
Chlorophyll does not absorb green
light.
That’s why plants appear to be
green.
Sunlight decreases during the fall
and winter.
It requires energy for plant cells to
make chlorophyll.
And, it is less useful when there is
little sunlight.
So, plants stop making chlorophyll
during the fall and winter.
When plants stop making
chlorophyll, you see the other
pigments in their leaves.
During spring and summer, plants
use their chlorophyll to make
glucose.
There are two reactions in
photosynthesis:
the light-dependent
reactions
and
the light-independent
reactions
What happens during the lightdependent reactions?
Sunlight is necessary, so these
happen during the day.
This step occurs in the the
chloroplast, specifically in the
thylakoid membrane
What happens during the lightdependent reactions occur?
Two Important Things:
1. Sunlight energy splits water to
form oxygen and 2 hydrogens.
2. Sunlight energy makes ADP into
ATP.
What happens during the lightdependent reactions occur?
1. Sunlight energy splits water to
form oxygen and 2 hydrogens.
H2O → 2H + O
These hydrogen are carried to the
next step and are used later and
oxygen is released as waste!
The hydrogen is transferred to
“carrier molecules” called NADP+
NADP+ turns into NADPH when
“carrying” a hydrogen
NADPH (Hydrogen Carrier)
• NADPH is found in light
dependent and
independent reactions.
• Light dependent turns
NADP+ into NADPH with
oxygen
• The Calvin cycle (light
independent reaction)
uses NADPH to form energy
sugars.
The hydrogen carriers provide
energy (and hydrogen!) to make
glucose
What happens during the lightdependent reactions occur?
2. Sunlight energy mades ADP into
ATP
ATP IS CHEMICAL ENERGY
ATP and NADPH provide the
energy that is needed to make the
bonds in glucose!
Sunlight is needed to complete
the light dependent reactions.
The light-independent reactions
can take place with or without
light.
What happens in the light
independent reaction?
Overall:
Energy from the hydrogen carriers (NADPH)
and the ATP made in the light-dependent
reactions are used in combination with
CO2 to make glucose
Where does the carbon and oxygen
in glucose come from?
Carbon
dioxide!
The light independent reaction
takes place in the chloroplast,
specifically, in the “stroma”
Let’s review!
The chemical equation for
photosynthesis is:
6CO2 + 6H2O → C6H12O6 + 6O2
Glucose will be used by the plant
cells to make ATP (energy)
This process is called Cell
Respiration
Glucose in plants is also used as
energy in the form of food for
other organisms
Sunlight
Photosynthesis “Boxes”
Putting it all together
C02
Light Dependent reactions
-Energy from light breaks
up water into 2H and O
and create ATP
-H bonds to the hydrogen
carrier (NADP+) to be used
later to become a part of
glucose
ADP and NADP+ Light independent reactions
-Known as the Calvin Cycle
-Uses the H of NADPH and the
ATP to break down CO2 and
create C6H1206
-Recycles ADP and NADP+ as
ATP and NADPH waste products to be used
again
H20
C6H1206
02
CHECK FOR
UNDERSTANDING
1. Where do plants obtain the reactants
that they need for photosynthesis?
CHECK FOR
UNDERSTANDING
1. Where do plants obtain the reactants
that they need for photosynthesis?
(Water from the soil, CO2 from the
atmosphere, light energy from the sun)
2. What do plants produce that we need to
survive?
CHECK FOR
UNDERSTANDING
1. Where do plants obtain the reactants
that they need for photosynthesis?
(Water from the soil, CO2 from the
atmosphere, light energy from the sun)
2. What do plants produce that we need to
survive?
(Oxygen gas and glucose)
3. What is the purpose of ATP?
CHECK FOR
UNDERSTANDING
1. Where do plants obtain the reactants that they
need for photosynthesis?
Water from the soil, CO2 from the atmosphere,
light energy from the sun
2. What do plants produce that we need to
survive?
Oxygen gas and glucose
3. What is the purpose of ATP?
It is a form of chemical energy that can be
required for many of our cells chemical
reactions.