Photosynthesis
Photosynthesis
Photosynthesis
Click below to see video
• http://www.youtube.com/watch?v=zEgIO9Kq2_Y
What organelle would you
expect to find in a plant cell
that you won’t find in an
animal cell?
• Chloroplasts!
What happens in the
chloroplast?
• Photosynthesis!
What is photosynthesis?
• Process of using energy
from the sun to convert
water and carbon
dioxide to
carbohydrates and
oxygen
Photosynthesis in Overview
• Process by which plants and other
autotrophs store the energy of sunlight
into sugars.
Why is that important to us?
• We need to eat and
breathe!
• Photosynthesis provides us with the
oxygen we need to breathe, and the
food we need to eat to obtain
energy !
What is an autotroph?
• Autotroph = organisms that make
their own food (plants and some
bacteria)
– Called producers (because they
produce food)
What is a heterotroph?
• Heterotroph = organisms that
gets it energy requirements by
consuming other organisms
(animals)
– Called consumers
Heterotrophs
• Heterotrophs that eat only plants
are herbivores
– Cows, rabbits, grasshoppers
• Heterotrophs that prey on other
heterotrophs are called carnivores
– Wolves, lions, hawks
• Heterotrophs that eat both plants and
animals are called omnivores
– Bears, humans, mockingbirds
• Heterotrophs that eat fragments of
dead matter are called detritivores
– Worms, aquatic insects that live on
stream bottoms
• Heterotrophs that break down dead
organisms by releasing digestive
enzymes and absorbing nutrients
are called decomposers
• Without Detritivores and
Decomposers, the entire biosphere
would be littered with dead
organisms!
Trophic levels
Steps in a Food
Chain
Trophic levels
• Autotrophs
make up first
trophic level
• Heterotrophs
make up the
remaining
trophic levels
What is energy?
• Energy is the ability to
do work.
• All living things need
energy!
• Without energy, life
would not exist!
Energy
• May be
Kinetic or
Potential
energy
21
Kinetic Energy
• Energy of
Motion
• Heat and light
energy are
examples
22
Potential Energy
• Energy of
position
• Includes
energy stored
in chemical
bonds
23
Cellular Energy
Cellular Energy
• Adenosine = adenine + ribose
• ATP - adenosine tri(3)phosphate used by the cell for energy
– Energy currency
– Energy stored in PO43- bonds
• ADP - Adenosine Di(2)phosphate used to regenerate ATP
ATP
• Components:
1. adenine: nitrogenous base
2. ribose: five carbon sugar
3.phosphate group: chain of 3
Phosphate
group
adenine
P P
ribose
P
How does ATP work ?
• Organisms use enzymes to
break down energy-rich
glucose to release its
potential energy
• This energy is trapped and
stored in the form of
adenosine triphosphate(ATP)
Coupled Reaction - ATP
• Energy used
for growth,
reproduction,
movement
and active
transport
• Drives most
of cell’s
activities
H2O
H2O
Hydrolysis of ATP
ATP + H2O 
ADP + P
(exergonic)
Adenosine
triphosphate (ATP)
P
P
P
Hydrolysis
(add water)
P
P
+
P
Adenosine diphosphate (ADP)
Hyrolysis is Exergonic
Energy
Used by
Cells
Copyright Cmassengale
Dehydration of ATP
ADP + P

(endergonic)
ATP + H2O
Dehydration
(Remove H2O)
P
P
+
P
Adenosine diphosphate
(ADP)
Adenosine triphosphate
(ATP)
P
P
P
Copyright Cmassengale
Dehydration is Endergonic
Energy is
restored
in
Chemical
Bonds
Copyright Cmassengale
Terminology Review
• Autotroph
– Obtains energy from light
• Heterotroph
– Obtains energy from other sources
• Trophic levels
– Ex. Sun – plant – herbivore – carnivore
• Photosynthesis
– Process by which light energy is
converted to chemical energy
• Cellular respiration
– Process used to harvest energy from
organic compounds
More to come!
Quiz next time
(8.1)
Terminology Review
• Autotroph
– Obtains energy from light
• Heterotroph
– Obtains energy from other sources
• Trophic levels
– Ex. Sun – plant – herbivore – carnivore
• Photosynthesis
– Process by which light energy is
converted to chemical energy
• Cellular respiration
– Process used to harvest energy from
organic compounds
Photosynthesis
Chapter 8.2
Photosynthesis
Overview
• Sun
– The source of energy for all
living things!
• Photosynthesis
– Taking in light energy and
changing it to chemical energy
– Occurs in the chloroplasts of
autotrophs
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
• Occurs in the leaves of plants in
organelles called chloroplasts.
+
6 O2
Leaf
Structure
• Gas exchange
of CO2 and O2
occurs at
openings called
stomata
surrounded by
guard cells on
the lower leaf
surface.
Chloroplasts
• Found in leaves of plants
• Site of photosynthesis
• Composed of:
– grana - stacks of thylakoids contain pigment (chlorophyll)
• site of light reaction
– stroma - the fluid around the
grana
• site of dark reaction
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Chloroplast Structure
• Inner
membrane
called the
thylakoid
membrane.
Chloroplast Structure
• Thickened
regions
called
thylakoids.
Chloroplast Structure
• A stack of
thylakoids
is called a
granum.
(Plural –
grana)
Chloroplast Structure
• Stroma is a
liquid
surrounding
the
thylakoids.
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Pigments
• Photosynthetic organisms capture
energy from sunlight with pigments
• These pigments are embedded in
the membranes of the chloroplast in
groups called photosystems.
Pigments
• Chlorophyll A is the most important
photosynthetic pigment.
• Other pigments are also present in the
leaf.
– Chlorophyll B
– Carotenoids (orange / red)
– Xanthophylls (yellow / brown)
Pigments
• Chlorophylls absorb most strongly in
the violet-blue region of the visible
light spectrum and reflect light in
the green region. That is why
plants that have chlorophyll a
appear green!
Light
• White light - spectrum of many colors
and wavelengths (ROYGBIV)
• Carotenoids absorb mostly blue and
green
– Reflects red, yellow, and orange
• Chlorophyll absorbs mostly blue and
red light
– Reflects green light
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More to come!
Quiz next time
(8.2)
Photosynthesis
Ch 8.3
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 (lightindependent) occur in the
stroma.
– Carbon dioxide is “fixed” into
the sugar glucose.
– uses ATP and NADPH
molecules created during the
light reactions to power the
production of this glucose.
Light Reaction
• Photosystem II (Grana, thylakoid
membrane)
– Light energy is absorbed by chlorophyll
– Energy transferred to an electron
– Excited electron exits to the Electron
Transport Chain
• Electron must be replaced
– Water molecules split
– Oxygen gas released
– ETC forms ATP
Light Reaction
• Photosystem I
– The electrons are energized again (more
light energy)
– Energy is transferred to change NADP+
into NADPH
• NADP+ is an electron carrier (takes
the high energy electrons to the
stroma for use in the light
independent reaction
Nicotinamide adenine dinucleotide phosphate
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From: http://www.cat.cc.md.us/~gkaiser
/biotutorials/photosyn/fg4.html
Products
• Products formed in the light reaction
– 1. Oxygen gas (O2) – released to
atmosphere
• From 2 water molecules being split
– 2. ATP – to dark reaction (stroma)
• From photosystem II
– 3. NADPH - to dark reaction (stroma)
• From photosystem I
Dark reaction
• Occurs in stroma of chloroplast
• Uses C & O from CO2 and H from
NADPH to form C6H12O6
• Uses energy from ATP and
NADPH
• Calvin Cycle
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Carbon Fixation:
• Carbon atoms from CO2 are
bonded or “fixed” into organic
compounds
• Carbon fixation: incorporation of
CO2 into organic compounds
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PGAL
From: http://lhs.lps.org/staff/sputnam/
Biology/U4Metabolism/calvincycle.png
Page: 69
Calvin cycle review
• What goes in
– 6 CO2
– 18 ATP
– 12 NADPH
• What comes out
– 1 glucose molecule
»ADP, NADP+
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Rate of Photosynthesis:
• Affected by:
– Light intensity
– CO2 Levels
– Temperature
– Availability of water
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Rate of Photosynthesis:
• Light intensity:
– as light intensity
increases, the
rate increases
and then levels
off
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From: http://ghs.gresham.k12.or.us/science/ps/sci/ib
bio/cellenergy/photosynnotes/photosyn/intensity.htm
Rate of Photosynthesis:
• CO2 Levels:
– increasing levels
stimulates rate
until plateau is
reached
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From: http://ghs.gresham.k12.or.us/science/ps/sci/i
bbio/cellenergy/photosynnotes/photosyn/dioxide.htm
Rate of Photosynthesis:
• Temperature:
– Raising temperature
accelerates rate
• Too hot - enzymes
denature
– Stomata will begin to
close, limiting water
loss and CO2 entry
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From: http://ghs.gresham.k12.or.us/science/ps/sci/
ibbio/cellenergy/photosynnotes/photosyn/temp.htm
Page: 74
Other Review
• Problem set 1
• Problem set 2
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More to come!
Quiz next time
(8.3)
How we use
the products
of
Photosynthesis
How do we use the glucose
and oxygen produced during
photosynthesis?
• We breath in the oxygen – it enters our
lungs, diffuses into our bloodstream, and
gets delivered to our cells.
• We eat food, the food breaks down into
molecules (remember learning about the
macromolecules in Ch 2?), diffuses into
our bloodstream, and then gets delivered
to our cells
• We can eat plants directly, (salads,
fruits, cereal, vegetables) or we
can eat meat from an animal that
ate the plants (hamburger, steak,
fish, chicken)
What happens once the
oxygen and glucose gets
delivered to our cells?
• Cellular respiration!
Cellular respiration
• C6H12O6 + 6O2
6 CO2 + 6H2O + 36 ATP
Remember the Photosynthesis equation?
Respiration is the process of extracting
stored energy from glucose and storing
it in the high energy bonds of ATP.
The cells
use ATPs
to do
cellular
work!
Cellular Respiration
• Happens in both Heterotrophs
and autotrophs
Cellular Respiration
• Takes place in 3 steps
1)Glycolysis
2)Krebs Cycle or Fermentation
3)Electron Transport Chain
(comes after Krebs Cycle)
Glycolysis
• Glycolysis occurs in all organisms!
– In the cytoplasm of their cells
• Glycolysis is the beginning of
cellular respiration.
• Does not require O2.
Glycolysis
• 1 glucose broken in half to form 2
pyruvic acid molecules (Pyruvate)
• Releases small amount of energy.
– Invest 2 ATP and get back 4
ATP - Net gain of 2 ATP
– Gain 2 NADH (from NAD+)
Glycolysis
• Occurs quickly- cells can produce
thousands of ATP molecules in
milliseconds!
– But this isn’t enough, we need more
from the respiration
• Does not require oxygen!
– Can supply chemical energy to cells
when O2 is not available.
Cellular Respiration
• After the pyruvic acid molecules
are formed during glycolysis, they
will go to Cellular Respiration
• There are two types of Respiration:
Anaerobic Respiration and Aerobic
Respiration
Vocab words!
• Anaerobic respiration
– No 02
• Aerobic respiration
– With 02
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Anaerobic Respiration
• FERMENTATION
• Occurs when in ABSENCE of O2.
• 2 Types
• Lactic acid fermentation
• Alcohol fermentation
Lactic Acid Fermentation
• Pyruvic acid is converted into
lactic acid
– NADH to convert pyruvic acid
to lactic acid
– H+ taken from NADH makes
NAD+
• used again for glycolysis
Examples
• Bacteria used to create sauerkraut
and buttermilk
• Build up of lactic acid in muscle
tissue.
– You feel the lactic acid when you feel
the ‘burn’ during exercise
Alcohol Fermentation
• Pyruvic acid converted into ethyl
alcohol in two steps
– 1. CO2 removed from pyruvic acid
• Uses NADH
– 2. H+ from NADH is transferred to
make ethyl alcohol
• Used again in glycolysis
• Enzymes break down glucose into
ethanol and CO2.
Examples
Bacteria and yeast – used to make:
• Wine
• Beer
• Cheese
• Bread
Next time we will learn
about Aerobic Respiration
Aerobic
Respiration
Remember
4/13/2015
Remember
• If oxygen is not available, after
glycolysis, the pyruvate goes into
anaerobic respiration, either lactic
acid or alcohol fermentation.
– Learned about this last class
Remember
• If oxygen is available, then the pyruvate
will go into the Mitochondria and aerobic
respiration
– Two parts, Kreb cycle and the electron
transport chain.
– We will learn about this today
The Mitochondria
• If O2 is present,
pyruvate is modified
and enters the
mitochondria.
• Here food is broken
down completely into
CO2.
• Energy storage
molecules like ATP are
produced. This is why
the mitochondria is
called the power house
of the cell.
Aerobic Respiration
• After glycolysis – 90% of the
energy that was in glucose is left
within the bonds of the pyruvate
• So in the presence of O2 pyruvate
passes to the second stage of
arerobic cellular respiration
within the matrix of the
mitochondria, the Krebs cycle
Krebs cycle
• Krebs cycle - named after Sir
Hans Krebs
• Also called the citric acid cycle
• Pyruvic Acid enters and ATP,
NADH, and CO2 exits
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Krebs cycle
• Once Pyruvate enters the
mitochondria, one carbon atom
becomes part of a molecule of
CO2
– Which will eventually be
released into the atmosphere
• The other two carbon atoms
become part of a molecule called
acetyl-CoA
• The Acetyl CoA will go through 2
turns of Krebs cycle
Krebs Cycle (Citric Acid Cycle)
1 Acetyl CoA (2C)
OAA (4C)
Citrate (6C)
Krebs
Cycle
FADH2
(one turn)
2 CO2
3 NAD+
FAD
3 NADH
ATP
ADP + P
Krebs Cycle (Citric Acid Cycle)
1 Acetyl CoA (2C)
OAA (4C)
Citrate (6C)
Krebs
Cycle
FADH2
(two turns)
2 CO2
3 NAD+
FAD
3 NADH
ATP
ADP + P
Krebs Cycle (Citric Acid Cycle)
• Total net yield (2 turns of krebs
cycle)
1. 2 - ATP
2. 6 - NADH
3. 2 - FADH2
4. 4 - CO2
Review of what we know so far
• Glycolysis:
– One glucose  2 pyruvic acids
and 2 NADH and 2 ATP
• Before Krebs:
– 2 Pyruvic acids  2 acetyl CoA,
2 NADH and2 CO2
• Krebs Cycle:
– Two turns produce:
• 6 NADH, 2 FADH2, 2 ATP, 4
CO2
Now to the Electron
Transport Chain!
Electron Transport Chain
• NADH and FADH2 from Krebs
move to the inner mitochondrial
membrane and their high energy
electrons convert ADP to ATP
as they travel through the
electron transport chain
inner mitochondrial
membrane
Electron Transport Chain
Site of
ETC
Outer
membrane
Inner
membrane space
Matrix
Cristae
Inner
membrane
115
Electron Transport Chain for
NADH
higher H+
concentration
ATP
+
H Synthase
Intermembrane Space
1H+
E
NADH
+ H+
NAD+
2H+
3H+
T
C
2H+ +
1/2O2
Inner
Mitochondrial
Membrane
H2O
ADP +P
H+
ATP
(Proton Pumping)
Matrix
116
Electron Transport Chain for
FADH2
higher H+
concentration
Intermembrane Space
+
1H
E
T
FADH2
+ H+
FAD+
ATP
+
H
+
2H
C
2H+ +
1/2O2
Synthas
e
Inner
Mitochondrial
Membrane
H2O
ADP + P
ATP
+
H
(Proton Pumping)
Matrix
117
Oxygen:
• O2 is the final electron acceptor
• Will also accept hydrogen ions
(protons – H+) from ETC (NADH
and FADH2)
– Forms H2O
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TOTAL ATP YIELD
1. 4 ATP – Glycolysis and Krebs Cycle
– Glycolysis: 2 ATP
– Krebs Cycle: 2 ATP
2. 32-34 ATP – Electron Transport Chain
36-38 ATP - TOTAL YIELD
• Actual number varies from cell to cell
• Aerobic respiration is 20x more efficient
than glycolysis alone
ATP
Cellular Respiration
Equation
• C6H12O6 + 6O2  6CO2 + 6H2O + 36ATP
Overview of photosynthesis and
respiration
SUN
RADIANT
ENERGY
PHOTOSYNTHESIS
GLUCOSE
RESPIRATION
CELL
ACTIVITIES
ATP(ENERGY)
EQUATION FOR
PHOTOSYNTHESIS
WATER
6CO2 + 6H2O +ENERGY
CARBON
DIOXIDE
OXYGEN
C6H12O6 +
6O2
GLUCOSE
EQUATION FOR
RESPIRATION
CARBON
DIOXIDE
GLUCOSE
C6H12O6 + 6O2
OXYGEN
ATP
6CO2 + 6H2O + ENERGY
WATER
Energy and Exercise
• Small amounts of ATPs are stored –
enough for a few seconds of intense
activity
• Then muscle cells will use ATPs made by
Lactic Acid Fermentation. This lasts
about 90 seconds (enough for a 200
meter sprint)
– The only way to get rid of the lactic
acid buildup is a chemical pathway that
requires extra oxygen. Reason for
heavy breathing after a race
Energy and Exercise
• For exercise more than 90 seconds,
cellular respiration is used for the needed
ATPs
• Slower than fermentation, so athletes
must ‘pace themselves’
• Uses glycogen stores for first 15 to 20
minutes
• Then uses other stored energy, like fats
• Why aerobic forms of exercise are
beneficial for weight control
End of Photosynthesis and
Respiration Power Point
You will see this again in
quizzes and tests!
Please Study!