Photosynthesis &
Respiration
What is Photosynthesis?
The process of photosynthesis is a
chemical reaction.
It is the most important
chemical reaction on our planet.
What is the Equation for the
Chemical Reaction of
Photosynthesis?
What is the equation for the
chemical reaction of
photosynthesis?
What is the equation for the
chemical reaction of
photosynthesis?
Six molecules of carbon dioxide react with
six molecules of water to form 1 molecule of
glucose and six molecules of oxygen.
Describe Photosynthesis
Photosynthesis
characteristics
• The process of changing light energy to
chemical energy
• Energy stored as sugar
• Occurs in plants and some algae
• Plants need light energy, CO2, and H2O
• Takes place in the chloroplasts, using
chlorophyll, the green pigment in plants
What happens during
photosynthesis?
What happens during
photosynthesis?
• Plants capture light energy and use that
energy to make glucose
• Sunlight provides the energy needed by
chlorophyll to change molecules of carbon
dioxide and water into glucose
• Oxygen is also released in this reaction
What happens during photosynthesis?
• Carbon dioxide enters the leaf through holes called
stomata
• CO2 combines with the stored energy in the
chloroplasts through a chemical reaction to make
glucose
• The sugar is moved through tubes in the leaf to the
roots, stems and fruits of the plants
• Some of the sugar is used right away by the plant
for energy; some is stored as starch; and some is
built into plant tissue
Why is this important to us?
Why is this important to us?
We cannot make our own food (glucose,
energy), we must get our food from plants.
Plants are the first step in the food chain.
Why is this important to us?
The oxygen released during photosynthesis
is necessary for all living things.
Stages of Photosynthesis
Photosynthesis is a two stage process. The first process is
the Light Dependent Process (Light Reactions), requires
the direct energy of light to make energy carrier molecules
that are used in the second process.
• The Light Independent Process (or Dark Reactions)
occurs when the products of the Light Reaction are
used to form C-C covalent bonds of carbohydrates.
The Dark Reactions can usually occur in the dark, if
the energy carriers from the light process are
present. Recent evidence suggests that a major
enzyme of the Dark Reaction is indirectly stimulated
by light, thus the term Dark Reaction is somewhat of
a misnomer. The Light Reactions occur in the grana
and the Dark Reactions take place in the stroma of
the chloroplasts.
What is Cellular Respiration?
What is Cellular Respiration?
The release of chemical energy for use by
cells. The molecule produced is ATP
• ATP is Adenosine Triphosphate. It is able
to store energy in the bonds between
phosphate groups.
• The “~” represents high energy bonds
Getting energy from Food
• Glucose is your main source of energy; the fuel
in your “cellular tank”
• Glycolysis is the beginning of the process
where the glucose is broken down.
• This process is anaerobic, no oxygen needed!
After Glycolysis
• Depending on the type of cell and whether
or not oxygen is present will result in
No oxygen
1. fermentation
Oxygen Present
2. cellular respiration
Anaerobic Respiration
• AKA “Fermentation”
• Why does fermentation happen?
– Not all cells have oxygen available
– Not all cells have the mitochondria to carry
out aerobic respiration
Products of fermentation
• Lactic Acid: C3H6O3
Products of fermentation
• Ethanol and CO2
Products of fermentation
• Acetic Acid: CH3COOH
• IF oxygen is present, and the organism is
able to perform cellular respiration, then
glycolysis is followed by AEROBIC
cellular respiration instead of
fermentation.
• The 3-carbon molecule (1/2 of the
glucose) moves into the mitochondria and
enters the mitochondrial matrix.
WOW!
Reaction: C6H12O6 + O2 ---> H2O + CO2 + 36ATP
• The electron transport chain requires
OXYGEN to work, the oxygen then
combines with hydrogen to form water.
What is Cellular Respiration?
Once the energy that was in sunlight is
changed into chemical energy by
photosynthesis, an organism has to
transform the chemical energy into a a
form that can be used by the organism.
This process is cellular respiration.
Describe Cellular Respiration
Describe Cellular Respiration
• The breakdown of glucose molecules to
release energy
• Takes place in all living things
• Is a step by step process
What is the chemical equation
for cellular respiration?
What is the chemical equation
for cellular respiration?
Read how photosynthesis &
respiration are related:
http://www.usoe.k12.ut.us/curr/science/scib
er00/8th/energy/sciber/photosyn.htm