ENERGY IN THE CELL
Usable Energy
 Energy is stored when bonds
are created and released when
bonds are broken.
 The molecule used by the cell
to transport energy from one
reaction to another is called
ATP (adenine triphosphate) .
 Phosphate groups have a
positive charge which means
they are difficult to force
together. By attaching three of
them together the cell stores a
lot of energy in the bond
created between the 2nd and
3rd phosphate.
Releasing Energy
 In order to use the energy
stored in ATP (perhaps to
put CO2 together into
sugar) the bond between
the 2nd and 3rd phosphate
is broken and the 3rd
phosphate is removed.
 When this occurs the
molecule left with 2
phosphates is called ADP
(adenine diphosphate)
and has little energy
stored.
A Reusable Cycle
 When energy is released
from ATP the ADP and
single phosphate are not
destroyed.
 ADP and the phosphate can
be attached back together
using the energy that comes
out of an exergonic reaction.
 This stored energy can then
be transported to any other
reaction as an energy
source.
 This makes ATP reusable
(like a rechargeable battery)
PHOTOSYNTHESIS
The Big Picture
 The process of photosynthesis is carried out by plants and
some unicellular organisms in order to use the energy from
light to assemble sugars. This will transform the light energy
into potential energy for the cell.
 This entire process will occur in the chloroplast.
 Step 1 the light dependent reaction occurs in the thylakoid.
 Step 2 the Calvin Cycle occurs in the stroma.
 During photosynthesis the cell will bring in light energy,
water, and carbon dioxide and use these reactants to create
oxygen and glucose (sugar).
 The chemical reaction is:
 Light + 6 H2O + 6 CO2  C6H12O6 + 6 O2
reactants 
products
Step 1: Light-dependent Reaction
 Water is brought into the
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thylakoid and broken apart to
remove electrons. The oxygen
from the water is released as a
byproduct.
The electrons are put into a group
of chlorophyll pigment called a
photosystem.
The photosystem collects light
energy in order to energize the
electron.
The electron passes down a series
of proteins imbedded in the
membrane.
As they travel down the electron
transport chain (ETC) the
electron’s energy is used to create
ATP which is the usable energy for
the cell.
Step 1: Light-dependent Reaction
 The electrons will end
up in a second
photosystem where
they receive more
energy from light and
are passed down
another ETC.
 At the end of the 2nd
ETC the electrons must
be stored so they do
not damage the cell.
The electron carrier
NADP+ will catch the
electron becoming
NADPH.
Step 2: The Light Independent Reaction
AKA The Calvin Cycle
 The energy in ATP and NADPH made in the
first reaction will be used to put CO2
together to make sugar in the second
reaction. Remember that creating bonds
requires and stores energy.
 The cycle will start with a 5 carbon molecule
called RuBP.
 Carbon dioxide is brought into the cell from
the environment and attached to the RuBP.
 At this point the energy made in the first
reaction is used to rearrange and break this
molecule in half creating two 3 carbon
molecules called PGAL.
 This will occur three times creating 6 PGAL.
Step 2: The Light Independent Reaction
AKA The Calvin Cycle
 At this point one of the PGALs
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is reserved while the remaining
five are rearranged back into
the three RuBPs that were
used.
The process repeats making 6
more PGAL.
Again one is reserved while the
other five are rearranged back
into RuBP.
The two PGALs that have been
reserved can now be attached
to create glucose.
This process took six turns of
the cycle. But, the RuBP was
recreated so process is able to
continue.
Recap
 Photosynthesis occurs in the chloroplast of plants and some unicellular
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organisms.
Photosynthesis uses light, water, and carbon dioxide to make oxygen
and sugar.
The chemical reaction is:
 Light + 6 H2O + 6 CO2  C6H12O6 + 6 O2
Step 1 The Light Dependent Reaction:
 Occurs in the thylakoid.
 Uses water and sunlight.
 Produces oxygen (which is released), ATP and NADPH (energy for
the next cycle).
Step 2 The Calvin Cycle:
 Occurs in the stroma.
 Uses ATP and NADPH breaking them into ADP and NADP+ to be
sent back to the first reaction for more energy. Also uses CO2 and
RuBP.
 Produces PGAL which is turned into glucose (sugar) and RuBP to be
reused.
Warm Up: Write and answer the
questions on pg 32
 What is the main function of photosynthesis?
 In what organelle does photosynthesis occur?
 What are the reactants of photosynthesis?
 What are the products?
 What can change the rate of photosynthesis and
how would the rate change?
 What types of organisms carry out photosynthesis?
plants
 Write out the reaction of photosynthesis.
 What is the main function of photosynthesis? Make
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sugar
In what organelle does photosynthesis occur?
chloroplast
What are the reactants of photosynthesis? Light,
water, and CO2
What are the products? Oxygen, sugar (glucose/starch)
What can change the rate of photosynthesis and how
would the rate change?
 Temperature: any temp other than optimum slows reaction
 Ph: any pH other than optimum slows reaction
 Amount of reactants: faster reaction with more reactants
 What types of organisms carry out photosynthesis?
plants
 Write out the reaction of photosynthesis.
 CO2 + H2O + LIGHT  C6H12O6 + O2
CELLULAR RESPIRATION
The Big Picture
 The process of cellular respiration is carried out by all
eukaryotic cells that can obtain oxygen to break down
sugar in order to create the energy molecule ATP.
 The majority of this process occurs in the mitochondria.
 Step 1 glycolysis occurs in the cytoplasm.
 Srep 2 the Kreb’s cycle occurs in the mitochondria.
 Step 3 the electron transport chain is attached to the inner
membrane of the mitochondria.
 During cell respiration the cell will bring in glucose
(sugar) and oxygen and produce carbon dioxide, water,
and ATP.
 The chemical reaction is:
 C6H12O6 + 6 O2  6 H2O + 6 CO2 + 36 ATP
reactants

products
Step 1 Glycolysis
 Occurs in the cytoplasm.
 The bond in the middle of glucose
is broken forming two 3 carbon
molecules called pyruvic acid.
 Like most chemical reactions,
glycolysis requires some
activation energy in the form of 2
ATP to start the reaction.
 Once the bond is broken the
electron that was being shared is
placed in an electron carrier called
NAD+ to make NADH. This way
the electron’s energy can be used
later.
 The energy that is released by the
breaking bond is used to create 4
ATP molecules meaning this step
makes 2 net ATP.
Step 2 Kreb’s Cycle
 The pyruvic acid made in the
first reaction is moved onto
the mitochondria.
 As the pyruvic acid is moved
one of the carbons is broken
off and released as CO2. The
breaking of this bond releases
another electron which is
placed on NAD+ making
NADH to be used later.
 The energy that was released
by the bond breaking is used
to form a new bond between
the remaining two carbons and
a coenzyme A to form AcetylCoA.
Step 2 Kreb’s Cycle
 Once Acetyl-CoA is made the
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molecule has the correct shape
to react with the enzymes in the
next part.
Through a series of chemical
reactions the Acetyl-CoA is
broken down. The remaining two
carbons are released as CO2.
The electrons from each broken
bond are placed into the
electron carriers NADH and
FADH2 so that their energy can
be used later.
The energy released from the
breaking of the bonds is used to
create 1 ATP.
Remember that there were 2
pyruvic acids so this process
occurs twice for a total of 2 ATP.
Step 3 Electron Transport Chain
 The electron carriers
NADH and FADH2 made in
the first steps are moved
to the inner membrane of
the mitochondria.
 The electrons are removed
and passed down a series
of proteins releasing a
little bit of energy at a
time.
 The energy released is
used to create 32 ATP.
 At the end of the ETC the
electrons are used to
create bonds between
oxygen and hydrogen to
make water.
Recap
 Cell respiration occurs mostly in the mitochondria of almost all
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eukaryotic cells.
Cell respiration breaks down sugar using oxygen to create water,
carbon dioxide, and 36 ATP molecules.
The chemical reaction is:
 C6H12O6 + 6 O2  6 H2O + 6 CO2 + 36 ATP
Step 1 Glycolysis: occurs in the cytoplasm
 Sugar is broken in half using 2 ATP. This creates pyruvic acid, 4 ATP
and NADH.
Step 2 Kreb’s Cycle: occurs in the mitochondria
 Pyruvic acid is broken down and released as CO2. The electron
carriers NADH and FADH2 as well as 2 ATP are also produced.
Step 3 ETC: occurs on the inner membrane of the mitochondria
 The electrons in NADH and FADH2 are placed into a series of
proteins where the energy is released a little at a time and used to
create 32 ATP. The electrons are then used to attach oxygen and
hydrogen together to make water.
Warm Up: write and answer the questions
on pg 32
 What is the main function of cell respiration?
 In what organelle does cell respiration occur?
 What are the reactants of cell respiration?
 What are the products?
 What can change the rate of cell respiration and
how would the rate change?
 What types of organisms carry out cell
respiration?
 Write out the reaction of cell respiration.
 What is the main function of cell respiration? Use
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oxygen to break down sugar to make ATP energy
In what organelle does cell respiration occur?
mitochondria
What are the reactants of cell respiration?
Glucose/sugar and oxygen
What are the products? Water, CO2, and 36ATP
What can change the rate of cell respiration and how
would the rate change?
 Temperature: any temp other than optimum slows reaction
 Ph: any pH other than optimum slows reaction
 Amount of reactants: faster reaction with more reactants
 What types of organisms carry out cell respiration? All
eukaryotic cells (animals AND plants)
 Write out the reaction of cell respiration
 C6H12O6 + O2  CO2 + H2O + 36ATP
FERMENTATION
The Big Picture
 Fermentation is a process used to
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break down sugar without oxygen.
There are situations (such as
sprinting) in which the cell does not
have enough oxygen to break down
sugar through cell respiration.
Some smaller organisms never
carry out cell respiration because
they do not require that much
energy and the alternative is faster.
While fermentation is faster it only
creates 2 ATP from a sugar
molecule. Therefore it is not as
efficient as cell respiration which
created 36 ATP for each sugar
molecule.
There are two kinds of fermentation
but each organism only carries out
one or the other.
Alcoholic Fermentation
 Occurs in the cytoplasm.
 Step 1: Glycolysis
 The bond in the middle of glucose is broken forming two 3 carbon
molecules called pyruvic acid. This requires 2 ATP, but it makes 4
ATP and NADH
 Step 2:
 The electron stored in NADH is used to break off a carbon as CO2
and rearrange the remaining two carbons into ethyl alcohol.
 Yeast and bacteria are the two most common organisms to carry out
alcoholic fermentation. We use fermenting yeast to make CO2 bubbles
causing bread to rise.
Lactic Acid Fermentation
 Occurs in the cytoplasm.
 Step 1: Glycolysis
 The bond in the middle of
glucose is broken forming
two 3 carbon molecules
called pyruvic acid. This
requires 2 ATP, but it makes 4
ATP and NADH
 Step 2:
 The electron stored in NADH
is used to rearrange pyruvic
acid into lactic acid.
 Human muscle cells will carry
out this type of fermentation for
quick energy or when there is
not enough oxygen to meet the
energy demands such as during
a sprint.