CELLULAR RESPIRATION AND
PHOTOSYNTHESIS
*The respiratory system carries oxygen to
the circulatory system.
*The circulatory system in turn, carries
oxygen to every cell in the human body.
AT THE CELL LEVEL
 Oxygen
is able to diffuse into the cell
while carbon dioxide diffuses out of the
cell.
 Once inside the cell, oxygen moves into
the mitochondria. -> the site of cellular
respiration
Glycolysis
without
oxygen
with
oxygen
An overview…
 Heterotrophs
and autotrophs go through the
process of cellular respiration to release the
energy stored in food.
 Before
autotrophs go through the process of
cellular respiration they have to go through
the process of photosynthesis to make their
own food.
 The
energy that is released during cellular
respiration is “packaged” in the form of ATP
(adenosine triphosphate).
CELLULAR RESPIRATION
 *During
cellular respiration, glucose
combines with oxygen to produce
carbon dioxide and water (and ATP).
C₆H₁₂O₆ + 6O₂
6CO₂ + 6H₂O + Energy
(Glucose + Oxygen
Carbon Dioxide +Water+ ATP)
 *For
heterotrophs (like us!) the
glucose comes from the food we eat.
ATP stands for adenosine tri-phosphate.
The bond linking the
last phosphate group is
a high energy bond.
When the third
phosphate is removed
and bonded to another
compound, it transfers
the energy to the other
compound.
THE PROCESS OF CELLULAR RESPIRATION
GLYCOLYSIS -> FIRST STEP IN CELLULAR RESPIRATION
*Glycolysis takes place in the cytoplasm. During
glycolysis, 1 glucose molecule is broken down
into 2 molecules of pyruvic acid.
*4 ATP molecules are formed; however, glycolysis
requires 2 ATP to break apart each molecule of
glucose; therefore, the net energy produced during
glycolysis is 2 ATP.
* If oxygen is present, glycolysis leads to two other
pathways; the Krebs cyle and the electron
transport chain. -> this is an aerobic pathway.
AEROBIC VS. ANAEROBIC RESPIRATION
 Aerobic
with oxygen
 Anaerobic
without oxygen
Aerobic respiration requires oxygen
and anaerobic respiration is carried
out without the presence of oxygen.
KREBS CYLE & ELECTRON TRANSPORT
CHAIN
 The
final two stages of
cellular respiration take
place in the
mitochondria.
 The Krebs cycle occurs in
the matrix of the
mitochondria.
 The electron transport
chain occurs in the inner
membrane of the
mitochondria.
During the Krebs cycle and the electron
transport chain, pyruvate is further
broken down and 34 more ATP are
produced.
FERMENTATION
 If
oxygen is NOT present, fermentation
occurs after glycolysis.-> this is an
anaerobic pathway
*
No ATP is produced during
fermentation; thus, all of the energy
generated during anaerobic respiration is
made during glycolysis.
FERMENTATION CONT.
 Alcoholic
Fermentation -> produces
ethyl alcohol and carbon dioxide
 Example -> yeast
 Lactic
Acid Fermentation -> produces
lactic acid and carbon dioxide
 Examples -> muscle cells, certain
bacteria
Glycolysis
without
oxygen
with
oxygen
REVIEW OF CELLULAR RESPIRATION
TRUE/FALSE
 1)
Cellular respiration that is carried out
without oxygen is aerobic. __________
 2) Glucose serves as a reactant during
cellular respiration. __________
 3) Heterotrophs obtain glucose as a product
of photosynthesis. ___________
 4) During cellular respiration, energy is
produced in the form of ATP. ___________
 5) The electron transport chain occurs during
aerobic respiration. ___________
REVIEW OF CELLULAR RESPIRATION
TRUE/FALSE
 6)
Glycolysis takes place in the
mitochondria. _______
 7) The process that breaks a glucose
molecule in half is fermentation.
________
 8) During aerobic respiration, the majority
of ATP is made in the mitochondria.
________
 9) Anerobic respiration is more efficient
than aerobic respiration at making ATP.
_______
 10) Yeast cells undergo fermentation. ____
PHOTOSYNTHESIS
PHOTOSYNTHESIS
Where does all of the
energy needed to
sustain life come
from?
____________________
The arrows below indicate the flow of ENERGY.
The sun gives off
energy in the form
of light and heat.
Plants are able to
absorb sunlight.
During
photosynthesis,
autotrophs (like
plants) use the
sunlight to
produce their
own food
(glucose).
Heterotrophs
(like us!) cannot
make their own
food -> they must
consume plants
and other
animals to obtain
glucose.
AUTOTROPHS VS. HETEROTROPHS
Autotrophs
are organisms that
make their own food from
inorganic substances.
Heterotrophs
are organisms that
cannot synthesize their own food
and must obtain in ready-made.
The following equation
summarizes the process
of photosynthesis.
Carbon
Dioxide + Water
Sunlight
Glucose + Oxygen
SOME DETAILS…
 The
process of photosynthesis begins
when light is absorbed by pigments
in the plant cell.
 The
most important photosynthetic
pigment in plants is chlorophyll: this
is what gives plants a green color
 Chlorophyll
is found in the chloroplasts ->
an organelle found only in plant cells
Mesophyll Cell
 More
specifically, chlorophyll is
found within the thylakoids of
chloroplasts.
SUMMARY OF PHOTOSYNTHESIS
1. Chlorophyll inside the chloroplasts
absorbs photons of light. (a photon is
a particle of light with a fixed
amount of energy).
2. The energy is used, along with
carbon dioxide, to blow water apart.
3. Glucose is produced.
4. Oxygen is released.
HOW DOES PHOTOSYNTHESIS RELATE
TO CELLULAR RESPIRATION?

*Photosynthesis
and cellular respiration
are complementary processes.
 Photosynthesis uses the energy of
sunlight to produce sugars.
 The same sugars in turn serve as food
(for both authotrophs and
heterotrophs).
 Cellular respiration uses O₂ and forms
CO₂ from the same carbon atoms that had
been taken in as CO₂ and converted into
sugars during photosynthesis.
REVIEW OF PHOTOSYNTHESIS
TRUE/FALSE
 1)
Heterotrophs can produce their own food.
__________
 2) The chemical equation for photosynthesis
is the opposite of the chemical equation for
cellular respiration. __________
 3) Photosynthesis uses the energy from
sunlight to produce water and carbon dioxide.
_________
 4) Photosynthesis occurs in the mitochondria.
__________
 5) It makes sense to talk to your plants.
__________