The Big Intro
• This is all about the relationship
between two chemical processes
found in living cells
• Autotrophs make nutrient
molecules, and
• Both Autotrophs and Heterotrophs
use these nutrient molecules for
their energy needs. This is cellular
respiration and comes later.
Photosynthesis
Photosynthesis in
Overview
• Process by which plants and other
autotrophs store the energy of sunlight into
sugars.
• Requires sunlight, water, and carbon
dioxide.
• Overall equation:
6 CO2 + 6 H20  C6H12O6 +
6 O2
• Occurs in the leaves of plants in organelles
called chloroplasts.
Leaf Structure
• Most photosynthesis occurs in the palisade
layer.
• Gas exchange of CO2 and O2 occurs at
openings called stomata surrounded by guard
cells on the lower leaf surface.
Palisade
Spongy
Chloroplast Structure
• Inner membrane
called the
thylakoid
membrane.
• Thickened
regions called
thylakoids. A
stack of
thylakoids is
called a granum.
(Plural – grana)
• Stroma is a liquid
Pigments
• Chlorophyll A is the most important
photosynthetic pigment.
• Other pigments called antenna or
accessory pigments are also present in
the leaf.
– Chlorophyll B
– Carotenoids (orange / red)
– Xanthophylls (yellow / brown)
• These pigments are embedded in the
membranes of the chloroplast in groups
called photosystems.
Photosynthesis: The Chemical
Process
• Occurs in two main phases.
– Light reactions
– Dark reactions (aka – the Calvin Cycle)
• Light reactions are the “photo” part of
photosynthesis. Light is absorbed by
pigments.
• Dark reactions are the “synthesis” part of
photosynthesis. Trapped energy from the sun
is converted to the chemical energy of sugars.
Light Reactions
• Light-dependent reactions occur on the
thylakoid membranes.
– Light and water are required for this
process.
– Energy storage molecules are formed.
(ATP and NADPH)
– Oxygen gas is made as a waste
product.
Dark Reactions
• Dark reactions (light-independent)
occur in the stroma.
– Carbon dioxide is “fixed” into the
sugar glucose.
– ATP and NADPH molecules created
during the light reactions power the
production of this glucose.
Photosynthesis
Let’s take a closer look
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How Plants Make Sugars
Pay attention; this is the
lesson!
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In this interactive lesson you will learn how
plants take carbon from the air to make glucose
Have you ever thought about where plants get the
energy to grow?
Is it from the soil?
Is it from the rain?
Or is it from the sun?
Let’s get started with navigation basics first
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Navigation – from here on out you:
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Lesson Menu
Lessons to learn:
1. ATP – The Energy Currency
2. Chloroplasts
3. Photosynthesis – Light Dependent Reactions
4. Photosynthesis – Light Independent Reactions
Assessment
LESSON 1
Have you ever used a rechargeable battery?
Well, every living thing uses the same molecule for the short-term
storage of energy. It is called ATP. The function of this molecule
can be compared to a rechargeable battery.
This molecule is called the energy currency
of ALL living things!
What does this word currency mean?
Let’s look to the web for a definition – click here  ?
So by calling ATP the energy currency of all cells
we mean that different parts of cells exchange
this molecule when energy is needed and consumed.
Since all living organisms use this same ATP molecule,
an analogy to this would be going anywhere in the world and being able to
buy goods with dollars, quarters, and nickels and other U.S. currency.
So how is this molecule like a re-chargeable battery?
Let’s find out!
This is a graphic representation of ATP
Notice the three main parts of ATP:
1. Adenine – a nitrogenous base
2. Ribose – a sugar
3. 3 Phosphate molecules
Go back and look at the ATP graphic again.
It also has a bond labeled a high-energy bond.
Do you remember what this implies?
Energy is stored in the bonds of molecules.
ATP is unstable.
(click on your answer)
That’s right!
Energy is stored in the bonds of molecules.
Remember from our unit on Biochemistry that whenever
chemical bonds are formed or broken energy is exchanged.
When bonds are broken energy is released
and generally, energy is needed to form bonds.
What about the re-chargeable battery analogy?
See if you can deduce the correct answer.
3 phosphates attached to the adenosine molecule represents
a fully charged battery, with a maximum number
of energy–rich chemical bonds.
The adenosine molecule itself is the fully charged battery.
(click on your answer)
Excellent!
When 3 Phosphates are attached to adenosine
this energy currency is at its highest denomination,
like a fully charged battery.
This molecule is again called adenosine triphosphate
or ATP.
The fewer phosphates, the less energy these molecules have
because they have fewer bonds from which to release energy.
Adenosine diphosphate
(Half-charged battery)
Adenosine monophosphate
(dead battery)
This concludes lesson 1.
LESSON 2
Photosynthesis
is
The absorption of light energy from the sun by specialized organelles.
That use this energy to power chemical reactions that
use water and “fix” carbon dioxide from the atmosphere
into energy storage molecules called glucose.
It is the occurrence of two successive series
of chemical reactions called:
1. Light dependent reactions
2. Light independent reactions
What was the specialized organelle we studied
in the cells unit where photosynthesis occurs?
Vacuole
Chloroplast
Good job!
Chloroplasts are the specialized organelle
in plants and some algae where photosynthesis occurs.
This view would be through
a cross-section of the leaf
The light dependent reactions (subject of lesson 3)
occur in the thylakoid membrane .
The light independent reactions (subject of lesson 4)
occur in the stroma.
The thylakoids (as seen in the graphic)
are arranged like a stack of coins called a granum, with
the side of the granum oriented towards the sun
for maximum light exposure.
This concludes lesson 2.
LESSON 3
As stated in lesson 2 photosynthesis involves water, CO2,
light energy and sugars, but let’s get more specific.
Let’s look at the chemical and
word formulas for photosynthesis.
6CO2 + 6H20 sunlight C6H12O6 + 6O2

Carbon dioxide + water sunlight glucose + oxygen
Next is a concept map of the whole process.
Concept Map
Photosynthesis
includes
Light
independent
reactions
Light
dependent
reactions
uses
Light
Energy
Thylakoid
membranes
to produce
ATP
NADPH
occurs in
occur in
Stroma
of
O2
Chloroplasts
uses
ATP
NADPH
to produce
Glucose
Here’s a graphic representation of the two
series of reactions.
The light dependent reactions capture
the energy of the sun.
The light-dependent reactions are comprised of
two sets of reactions called photosystems.
Photosynthesis begins with Photosystem II
because it was the first set of reactions discovered.
Photosystem II
Begins with absorption of energy (photon) by a chlorophyll molecule (Chl).
The chlorophyll molecule is raised to an excited state.
The electron lost by the chlorophyll is replaced by
the enzymatic splitting of water
This electron is passed down a chain of molecules
called the electron transport chain or redox chain.
Energy from this transfer of electrons is used to
produce ATP, leaving the electron in a low energy
state to be recharged by Photosystem I
The low energy electron from photosystem II
replaces one that in photosystem I that has
become energized and left the chlorophyll
Molecule in photosystem II.
Energy from this excited electron is exchanged
across different molecules (called carriers)
ultimately being used to convert NADP+ to
NADPH.
NADPH stores this electrical energy for use in
the light independent reactions.
The Light Dependent Reactions
(Overview)
Where did the light dependent reactions
take place again?
In the stroma
In the thylakoid membranes
Correct!
This completes lesson 3
LESSON 4
Let’s Review
The two series of chemical reactions that comprise
Photosynthesis are called?
Photosystem I and Photosystem II
Light dependent and Light independent
Correct!
The two series of chemical reactions that comprise
photosynthesis are called the:
Light dependent reactions – they require light and therefore occur
in the thylakoid membrane
Light independent reactions – these don’t require light and occur
in the stroma
Light Independent Reactions
(also called Calvin Cycle, after man who discovered them)
Are a cyclical set of reactions that use the CO2 from the
atmosphere to make the high energy sugar glucose
Take a look at the overview of photosynthesis again
Here’s an overview of the Calvin Cycle.
Next we’ll break it down in stages.
The quantities listed are for the production of one glucose
molecule which is produced from six turns of the cycle
Acronyms we’ll use
RuBP - ribulose biphosphate
PGA - phosphoglycerate
PGAP - diphosphoglycerate
PGAL - phosphoglyceraldehyde
The cycle starts when (3) 5-carbon molecules
(from the previous cycle) of RuBP combine with
(3) CO2.molecules from the atmosphere.
This combination of molecules forms six molecules
of the 3-carbon compound PGA.
The energy and phosphates from six ATP’s
is taken to convert the 6 PGA’s to 6 PGAP’s
Where did these ATP’s come from?
The Light dependent reactions
The mitochondria
You are right!
In this next step the energy from 6 NADPH’s
is used to remove the phosphate molecules
forming 6 PGAL’s
Where did these NADHP’s come from?
The cytoplasm
The Light dependent reactions
You are correct!
At this point (after three turns of the cycle)
one of these PGAL’s leaves the cycle.
Six turns of the cycle produces 2 of
these PGAL molecules which combine
to form a glucose molecules.
The remaining 5 PGAL molecules are converted
to (3) 5-carbon intermediates, then back to 3
RuBP molecules to start the cycle again.
This completes lesson 4
ASSESSMENT
Question 1 of 5
The energy currency of all cells in all organisms is
Adenosine diphosphate
Adenosine triphosphate
Adenosine monophosphate
Correct
Continue on to Question 2
ASSESSMENT
Question 2 of 5
The two series of chemical reactions that comprise
photosynthesis are called
Photosystem I and photosystem II
Cellular Respiration
Light dependent and light independent
Correct
Continue on to Question 3
ASSESSMENT
Question 3 of 5
The light independent (also called dark reactions)
occur in the)
stroma
thylakoid membrane
cytoplasm
Correct
Continue on to Question 4
ASSESSMENT
Question 4 of 5
The three parts of ATP are
adenine, thylakoids, stroma
stroma, grana, chlorophyll
adenine, ribose, phosphate
Correct
Continue on to Question 5
ASSESSMENT
Question 5 of 5
What are products of the light dependent reactions?
oxygen gas
ATP
NADPH
All of the above
Correct
You have now completed the test.
Return to Title Slide
Move on to Respiration
Incorrect
Go back and select the correct answer.
Cellular Respiration
• Now let’s see what all the
excitement is about in the release
of energy in cells
Respiration
• Respiration the process by which
food molecules are broken down
– Food molecules are 6-carbons sugars
– You take in food which is digested
and broken down into 6-carbon
sugars
– Plants can’t “eat” so they make 6carbon sugars with photosynthesis
– Mitochondria then transform the “food
energy” into chemical energy
Respiration
• A 6-carbon sugar contains an
enormous amount of energy (for a
cell)
• Mitochondria “make change”
energetically ($100 bill to 20 $5 bills
- easier to spend)
• Take the energy in a complex sugar
and convert it into more
conveniently-sized packages of
adenosine triphosphate
Respiration
C6H12O6 + 6O2 → 6CO2 + 6H2O + energy
Carbohydrate
Oxygen
Carbon
dioxide
Water
Respiration
• Aerobic respiration: processes that
require oxygen in order to take
place
• Anaerobic respiration: processes
that do not require oxygen
Aerobic Respiration
•
•
•
•
Step 1: Glycolysis
Step 2: Breakdown of pyruvic acid
Step 3: Citric acid cycle
Step 4: Electron transport chain
Respiration
CYTOPLASM:
Glycolysis
Outer membrane
MATRIX:
Breakdown of
pyruvic acid,
Citric acid cycle
INNER MEMBRANE:
Electron transport
chain
Step 1: Glycolysis
• Occurs in cytoplasm
• Does not require oxygen
• Involves splitting a glucose (6carbon sugar) into 2 3-carbon
molecules: pyruvic acid
Step 1: Glycolysis
• Also produces H+ ions and
energizes electrons which are
captured by NAD+, forming NADH +
H+
Step 1: Glycolysis
• Uses up 2 ATP
• Produces 4 ATP
• Net yield = 2 ATP
Step 1: Glycolysis
Glucose
Step 1: Glycolysis
2 ATP
Glucose
2 ADP
Step 1: Glycolysis
2 ATP
2 ADP
P
Glucose
P
2 PGAL
Step 1: Glycolysis
2 ATP
2 ADP
4ADP + 4 Pi
4ATP
P
Glucose
2 NAD+ 2NADH + 2H+
P
2 PGAL
Step 1: Glycolysis
2 ATP
2 ADP
4ADP + 4 Pi
4ATP
P
Glucose
2 NAD+ 2NADH + 2H+
P
2 PGAL
2 Pyruvic
acid
Aerobic Respiration
Step 1: Glycolysis
• Step 2: Breakdown of pyruvic acid
• Step 3: Citric acid cycle
• Step 4: Electron transport chain
Step 2: Breakdown of
Pyruvic Acid
• Occurs when pyruvic acid (from
glycolysis) enters the mitochondrial
matrix
• Requires oxygen
– If there is no oxygen present pyruvic
acid enters fermentation
Step 2: Breakdown of
Pyruvic Acid
• Involves breaking CO2 off pyruvic
acid
• Remaining portion of pyruvic acid
combines with coenzyme A to form
acetyl-CoA
Step 2: Breakdown of
Pyruvic Acid
• Also produces H+ and energizes
electrons which are captured by
NAD+, to form NADH + H+
Step 2: Breakdown of
Pyruvic Acid
Mitochondrial
membrane
To citric
acid
cycle
“Exhaled”
Aerobic Respiration
Step 1: Glycolysis
Step 2: Breakdown of pyruvic acid
• Step 3: Citric acid cycle
• Step 4: Electron transport chain
Step 3: Citric Acid Cycle
• Occurs in mitochondrial matrix
• Acetyl-CoA is transformed into citric
acid through a series of reactions
Step 3: Citric Acid Cycle
• More ATP and CO2 are produced
• More H+ are produced and
electrons are energized
• NAD+ and FAD capture them to
form NADH + H+ and FADH
Step 3: Citric Acid Cycle
4C
6C – Citric acid
CITRIC
ACID
CYCLE
5C
Aerobic Respiration
Step 1: Glycolysis
Step 2: Breakdown of pyruvic acid
Step 3: Citric acid cycle
• Step 4: Electron transport chain
Step 4: Electron Transport
Chain
• Happens on inner membrane of
mitochondria
• Occurs only if oxygen is present
– Oxygen is final electron acceptor
– If no oxygen is present reaction stops
Step 4: Electron Transport
Chain
• Electrons come from NADH and
FADH molecules which gathered
them during glycolysis and CTA
• Energy from electrons is used to
add Pi to ADP, forming ATP
• At the end of the chain, oxygen
accepts the electrons and
combines with 2 H+ ions to form
water
Step 4: Electron Transport
Chain
Aerobic Respiration
•
•
•
•
Step 1: Glycolysis
Step 2: Breakdown of pyruvic acid
Step 3: Citric acid cycle
Step 4: Electron transport chain
Aerobic Respiration
Glycolysis
2
ATP
Citric acid cycle
2
ATP
Electron transport chain **32
ATP
**Makes ATP from electrons carried
to it from the first 3 steps
Aerobic Respiration
Makes 36
ATP
Anaerobic Respiration
• Pyruvic acid molecules are still
formed through glycolysis
• Broken down differently:
– No ATP is produced after glycolysis
– NAD+ is regenerated so glycolysis can
continue
Anaerobic Respiration
• 2 types:
– Lactic acid fermentation
– Alcoholic fermentation
Lactic Acid Fermentation
• Lactic acid is end product
• Occurs when muscles require
energy at a faster rate than it can
be supplied through aerobic
respiration
• Causes burning sensation in
muscles
Lactic Acid Fermentation
Glycolysis
Alcoholic Fermentation
• Ethyl alcohol and CO2 are end
products
• Occurs in organisms that live in
environments lacking oxygen
• Source of bubbles in beer and
champagne and causes baking
bread to rise
Alcoholic Fermentation
Glycolysis
2 CO2
2 Ethanol