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CH 8/9 NOTES
Photosynthesis and Cellular
Respiration
Chemical Energy
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
Energy is the ability to do work.

Your cells are busy using energy to build new
molecules, contract muscles, and carry out
active transport.

Without the ability to obtain and use energy, life
would cease to exist.
ATP/ADP
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 One
of the most important compounds that cells use
to store and release energy is adenosine
triphosphate (ATP).
 ATP
consists of adenine, a 5-carbon sugar called
ribose, and three phosphate groups.
Why is ATP useful to cells?
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ATP can easily release and store energy by
breaking and re-forming the bonds between its
phosphate groups. This characteristic of ATP
makes it exceptionally useful as a basic energy
source for all cells.
Storing Energy
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Adenosine diphosphate
(ADP) has two phosphate
groups instead of three.
ADP contains some enrgy,
but not as much as ATP.

.
Storing Energy
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
How is ADP like a
rechargeable battery? it
can store small amounts
of it by adding phosphate
groups to ADP, producing
ATP. Energy is released
by breaking the bonds
between the 2nd and 3rd
phosphate groups.
Using Biochemical Energy
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
One way cells use the energy provided by ATP
is to carry out active transport in order to run
the protein pumps.
Using Biochemical Energy
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
ATP powers movement, providing the energy
for motor proteins that contract muscle and
power the movement of cilia and flagella.
Using Biochemical Energy
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 Energy
from ATP powers the synthesis of proteins
and responses to chemical signals at the cell
surface.
Using Biochemical Energy
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
ATP is not a good molecule
for storing large amounts of
energy over the long term. It
is more efficient for cells to
keep only a small supply of
ATP on hand.

Cells can regenerate ATP
from ADP as needed by using
the energy in foods like
glucose.
Heterotrophs and Autotrophs
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
Organisms that obtain food by consuming other
living things are known as heterotrophs.
Examples
 Some heterotrophs get their food by eating plants.

Other heterotrophs, such as a cheetah, obtain food
from plants indirectly by feeding on plant-eating
animals.

Still other heterotrophs, such as mushrooms, obtain
food by decomposing other organisms.
Heterotrophs and Autotrophs
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
Organisms that make their own food are called
autotrophs.
Where do they get their energy? Sunlight!
(or chemicals in deep sea vents)
3 examples of autotrophs
 Plants, algae, and some bacteria are able to
use light energy from the sun to produce food.
(photosynthesis)
PHOTOSYNTHESIS
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Photosynthesis is changing the energy of
sunlight into chemical energy stored in the
bonds of carbohydrates.
Light



Sunlight is a mixture of different energy
wavelengths, many of which are visible to our eyes
and make up the visible spectrum.
List the colors we see in wavelength order:
Violet, blue, green, yellow, orange, red
Pigments
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
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Plants gather the sun’s energy with lightabsorbing molecules called pigments.
The plants’ principal pigment is chlorophyll.
Leaves reflect green light, which is why
plants look green.
Pigments
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 The
chlorophyll absorbs all colors of light except
for green. Chlorophyll reflect green light, which is
why plants look green.
Pigments
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 As
temperatures drop the chlorophyll molecules
break down, and the red and orange pigments
may be seen.
Review
 What
is the difference between ATP and ADP?
 What are the three parts of ATP?
 What is the difference between an autotroph and
a heterotroph?
 Explain how the pigment chlorophyll works.
 Why are plants green?
 Why do plants turn other shades of color as
seasons progress?
Chloroplasts
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Photosynthesis takes place (cross out “on”) in
autotrophs inside organelles called chloroplasts.
Chloroplasts contain saclike photosynthetic
membranes called thylakoids, which are
interconnected and arranged in stacks known as
grana.
Chloroplasts
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Pigments are located in the thylakoid membranes.
The fluid portion outside of the thylakoids is
known as the stroma.
Energy Collection
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
Because light is a form of energy, any compound
that absorbs light absorbs energy. Chlorophyll
absorbs visible light especially well.
When chlorophyll absorbs light, a large fraction of
the light energy is transferred to electrons. These
high-energy electrons make photosynthesis work.
An Overview of Photosynthesis
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
Photosynthesis uses the energy of sunlight to
convert water and carbon dioxide into high-energy
sugars and oxygen.
In symbols:
Chemical Equation:
 6 CO2 + 6 H2O  C6H12O6 + 6 O2
In words:
 Carbon dioxide + Water  Sugars + Oxygen
Factors Affecting Photosynthesis
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Temperature
The reactions of photosynthesis are made possible
by enymes that function best between 0 degrees C
And 35 degrees C.
Temperatures above or below this range may affect
those enzymes, slowing down or stop entirely.
Factors Affecting Photosynthesis

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Light
High light intensity increases the rate of
photosynthesis.
After the light intensity reaches a certain level,
however, the plant reaches its maximum rate of
photosynthesis.
Factors Affecting Photosynthesis
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And Water
Because water is one of the raw materials in
photosynthesis, a shortage of water can slow or
even stop photsynthesis.
Plants that lie in dry conditions often have waxy
coatings on their leaves to reduce water loss. They
may also have biochemical pathways that make
photosynthesis more efficient under dry conditions.
Light-Dependent Reactions
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
Photosynthesis involves two sets of reactions:
Light-dependent reaction
 Light-Independent reaction(also known as the Calvin
Cycle)

Light-Dependent Reactions
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Depends on light and water.
 Takes place in the thylakoid membranes of the
chloroplasts.
 They produce oxygen and convert ADP and NADP+
into the energy carriers ATP and NADPH.

Light Dependent Reactions
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Generating ATP and NADPH
What is a photosystem?
Photosystem II, energy from light is absorbed by
chlorophyll and transferred to electrons, and then
these high energy electrons are passed on to the
electron transport chain
Photosystem I-pigments use energy from light to
reenergize the electrons.
Light-Independent Reactions
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energy (ATP) from light reaction is required to power
the light-independent reactions (The Calvin Cycle!)
 Plants absorb carbon dioxide from the atmosphere
and produce glucose and other carbohydrates.
 The light independent reactions take place outside the
thylakoids, in the stroma
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Light Independent Reactions
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Producing Sugars
The common name for the light-independent reactions is
the Calvin Cycle.
What is being made in the reaction? Glucose!
The Calvin Cycle:
How many new carbon molecules are produced for
every 6 carbon dioxide molecules? A single 6 carbon
sugar molecule.
What are these molecules used for? To build more
complex carbs that the plants need for growth and
development.
The End Results
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The two sets of photosynthetic reactions work
together
The light dependent reactions trap the energy of
sunlight in chemical form.
The light independent reactions (The Calvin Cycle)
use that chemical energy to produce high-energy
glucose from carbon dioxide and water.
In the process, animals, including humans get food
and an atmosphere filled with oxygen.
Chapter 9
Cellular Respiration
Review
 What
is the equation for photosynthesis?
 What are the two reactions for photosynthesis?
Where do they occur?
Cellular Respiration
 Cellular
Respiration is the process that releases
energy from food in the presence of oxygen.
 Food molecules contain chemical energy that is
released when its chemical bonds are broken.
 Energy stored in food is expressed in amount of
calories.
 What is a calorie? The amount of energy needed
to raise the tempearutre of 1 gram of water 1
Celsius degree. (the calories used in food labels is
a kilocalorie, or 1,000 calories.)
Overview of Cellular Respiration
 Location:
Mitochondria (powerhouse of the cell)
 Purpose: Turn chemical energy (food) into usable
energy (ATP)
 Chemical Equation:
In symbols: C6H12O6 + 6 O2 6 CO2 + 6 H2O
In words: glucose + oxygen ----carbon
dioxide + water + Energy
3 stages of Cellular Respiration in
order
Glycolysis
Krebs
Cycle
Electron Transport Chain
Glycolysis (stage one)
Means: Split glucose
 Reactants (Input): Glucose
 Products (Output): 2ATP and Pyruvates

Note: pyruvates are often called pyruvic acid
Glycolysis
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Glycolysis produces only a small amount of energy.
Most of glucose’s energy (90 %) remains locked in
the chemical bonds of pyruvic acid at the end of
glycolysis.
Glycolysis is an anaerobic process. It does not
directly require oxygen,nor does it rely on an
oxygen-requiring process to run.
Glycolysis takes place in the cytoplasm of the cell.
Glycolysis
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What are the advantages of glycolysis?
1. process is fast
2. does not require oxygen
Oxygen and Energy
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Pathways of cellular respiration that require oxygen
are called aerobic.
The Krebs Cycle and the Electron Transport chain
are both aerobic processes.
Both processes take place inside the mitochondria.
Krebs or Citric Acid Cycle
Reactant: Pyruvate and
oxygen
 Product: 2ATP and CO2

Other name?-The Citric
Acid Cycle-citric acid is
produced
Electron Transport Chain
Location: Mitochondria
 Reactant: Oxygen
 Oxygen acts as an
electron receptor.
 Product: 32 ATP and
H2O
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Energy Totals
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How many ATP molecules are made by cellular
respiration? 36
Where do they come from (what stage?). 2 ATP’s
from glycolysis, 34 from the Krebs cycle and the
Electron Transport Chain
Sources besides glucose to generate ATP?
1. alcoholic fermentation 2. lactic acid fermentation
3. glycogen
Relationship

Opposite processes
Relationship
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
Photosynthesis is about
energy capture where
cellular respiration is
about energy release.
36% of energy from
glucose is given off as
ATP which leaves 64%
given off as heat.
Comparing Photosynthesis and Cellular
Respiration
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Reactants- Photosynthesis: Carbon Dioxide and
Water
Reactants-Cellular Respiration: glucose and oxygen
Products-Photosynthesis: Glucose and Oxygen
Products-Cellular Respiration: carbon dioxide, water
and ATP
Photosynthesis occurs in the chloroplast
Cellular Respiration occurs in the mitochondria
Review
 What
is the equation for cellular respiration?
 What are the three reactions for cellular
respiration? Where do they occur?
 What are all the inputs for cellular respiration?
 What are all the outputs for cellular respiration?
 What is the relationship between photosynthesis
and cellular respiration?
Fermentation
What is fermentation?
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In the absence of oxygen there
is no cellular respiration,
fermentation occurs and small
amounts of ATP (energy) will
be created in order to keep
the cell from dying.
Where? The cytoplasm
Two kinds of fermentation
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Lactic Acid Fermentation
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Alcoholic Fermentation
Alcoholic Fermentation
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Produces alcohol, carbon dioxide, and 2 ATP
Example:
 Bread/yeast:
This process causes bread dough to rise and
the carbon dioxide released causes the holes in bread.
 This is how alcoholic beverages are created.
Lactic Acid Fermentation
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Produces lactic acid and 2 ATP
Example:
 Muscle
Cells: Fermentation occurs during heavy exercise
 Bacteria: Some help to make yogurt and cheese
Energy/Exercise
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Quick Energy
 Cells
normally contain small amounts of ATP
produced during cellular respiration, enough for
quick burst of intense activity.
 Lactic Acid Fermentation can supply enough ATP to
last about 90 seconds. However, extra oxygen is
reuqired to get rid of the lactic acid produced.
 Following intense exercise, a person will “huff and
puff” for several minutes to pay back the built up
“oxygen- debt” and clear the lactic acid from the
body.
Energy/Exercise
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Longer exercises
Fermentation only makes enough energy to last 90
seconds
 Exercise longer than this can only get the energy it needs
from cellular respiration.
 The body stores energy in the form of the carbohydrate
glycogen. These glycogen stores are enough to last for
15 to 20 minutes of activity. After that, the body begins
to break down other stored molecules, including fats, for
energy. This is how animals can hibernate by living off of
stored fats.

Review
 When
does fermentation occur?
 What are the two types of fermentation?
 For each type:
 What
are the inputs?
 What are the outputs?