Introduction
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ALL cells need energy and matter for growth
and reproduction.
Some organisms (like plants) obtain their
energy directly from the Sun.
Other organisms must consume food to
obtain energy.
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Autotrophs: self feeders,
organisms capable of making
their own food
Photoautotrophs: use
photosynthesis = makes
organic compounds (glucose)
from light. Converts sun
energy into chemical energy
usable by cells.
Chemoautotrophs: use
chemosynthesis = makes
organic compounds using
energy from the oxidation of
inorganic chemicals, such as
sulfur released from deep
hydrothermal vents.
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Energy = Capacity to do work
Potential Energy = Stored energy (the energy
must be released for it to do any work e.g.
apple hanging by a stem)
Kinetic Energy = The energy of motion (apple
falling to the ground)
Chemical Energy = Energy stored in the bonds
of molecules. Type of potential energy. Once
the chemical bonds are broken, the atoms have
extra kinetic energy. The atoms can move, do
work, make things happen!
The CARBON
CYCLE
1.
Photosynthesis = light energy from the Sun is
used to transform carbon dioxide and water into
energy-rich food molecules.
CO2 +
H2O
Carbon
Dioxide
Water
Light
Energy
C6H12O6 + O2
Glucose
Oxygen
2. Cellular Respiration = all of the chemical reactions
needed to break down (metabolize) carbohydrates
(and other molecules) to transfer chemical energy to
ATP.
ADP
C6H12O6 + 6O2
Glucose
Oxygen
ATP
6H2O + 6CO2
Water
Carbon
Dioxide
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Involves over 100 chemical
reactions.
The overall process happens in two
main stages:
 1. PHOTO stage: light dependent
 2. SYNTHESIS stage: light
independent
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Splits water and produces ATP.
Photosystem reactions need light energy.
Stores chemical energy in the bonds of glucose.
Synthesis reactions need chemical energy (ATP)
and H+ from photo stage.
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Carbon dioxide and water plus light energy
are the raw materials of photosynthesis.
Enzymes and chlorophyll are accessories that
are needed to make photosynthesis occur
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Visible and Invisible radiation
from the Sun and other sources of
radiant energy.
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Radiowaves, microwaves, x-rays, etc
Visible radiation is usually
simply called LIGHT.
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All forms of electromagnetic radiation travel
at 300 000 000 m/s
Different frequency of light results in
different wavelengths, which are perceived as
different colours.
The highest frequency of light is violet and
the lowest frequency is seen as red.
A combination of all of the frequencies is
interpreted as White light.
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Light travels through space in
the form of individual energy
“packets” called photons.
The amount of energy in a
photon depends on the
frequency of light. The higher
the frequency the more energy
the photon is able to deliver.
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More energy in a photon of violet than
in red.
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To use the energy of light for
photosynthesis, a plant must
absorb photons of light.
Molecules that absorb light are
called Pigments.
Most plant leaves contain
chlorophyll pigments which give
leaves their green colour.
Absorption is only one of three
possible outcomes when light
strikes a surface.
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The other two are reflection and
transmission
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Photosynthesis takes place in
chloroplasts
Chloroplasts contain light
absorbing pigment molecules
(chlorophyll a & b)
Chlorophyll absorbs red, violet,
and shades of blue.
The chlorophyll passes the
energy onto other molecules that
can be used by the synthesis
reactions.
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Very small – 40 chloroplasts in 1mm.
Very powerful - perform hundreds of reactions
in just 1 second.
Has a double membrane.
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Folded THYLAKOID membranes form stacks
known as GRANA. The folding increases the
surface area for reactions to occur.
Inside the thylakoid is a space called the
LUMEN
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In and around the grana is a watery substance
called STROMA
The chloroplast also contains lots of ENZYMES.
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Light energy is used to
split water molecules
(photolysis) to form
oxygen and hydrogen
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Oxygen atoms (O2) are
released into the
atmosphere
Hydrogen atoms added to
NADP to make NADPH+
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Oxygen molecules pass
out the chloroplast
membrane into the cell’s
cytoplasm.
Most of the oxygen that is
produced is waste product.
The plant’s own cells use
some of the oxygen to
carry out cellular
respiration.
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Chlorophyll pigments
are packed into clusters
called
PHOTOSYSTEMS
Photosytems funnel
absorbed energy to the
REACTION CENTER
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Excited electrons are
passed from the primary
electron acceptor to
ELECTRON TRANSPORT
CHAINS
The electrons “fall” to a
lower energy state,
releasing energy that is
harnessed to make ATP.
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Adenosine triphosphate
One molecule of ATP contains
three phosphate groups
When removing the third
phosphate group, lots of
energy given off
An EXCELLENT molecule for
shuttling energy around
within cells.
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Nicotinamide adenine
dinucleotide phosphate
NADPH is the reduced form
of NADP+.
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Reduction is the gain of electrons
by a molecule, atom, or ion
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Does not require sunlight
Requires 18 ATP's, 12 NADPH's,
and CO2 to produce glucose
Uses the products from the Light
Reaction
Occurs in the STROMA of the
chloroplast
Three phases of the Dark
Reaction
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Carbon Fixation
Reduction
Regeneration
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Carbon fixation is a process
which involves the conversion of
carbon in a gas to carbon in solid
compounds.
In order for carbon fixation to
occur, energy in the form of ATP
and hydrogen (from photolysis)
are needed.
The carbon can be used to make
organic compounds.
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The carbon of a CO2 molecule from the
atmosphere is attached to a 5-carbon sugar
called RuBP
This forms an unstable 6-carbon compound
The 6-carbon compound breaks down to form
two 3-carbon molecules called
PGAL(phosphoglyceraldehyde)
 Think of PGAL as half a glucose
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The 3 PGAL are converted to G3P using
energy (ATP) and hydrogens from NADPH
from the Light Reaction
For every 3 molecules of CO2 there are 6
molecules of G3P produced
 Only 1 is net gain
 What happens to the other 5?
 Regeneration
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Products need to be regenerated to keep the
cycle going.
5 of the 6 G3P molecules are regenerated
using ATP and producing 3 RuBP molecules
which are then ready to receive new CO2 and
continue the cycle
The one G3P molecule combined with
another G3P molecule is used to make
glucose, fructose, sucrose, starch and cellulose
for the plant.
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Describes how much sugar a plant can
produce over time
It describes how productive a plant is under
various conditions
What things would control the rate of
photosynthesis?
1. Light Intensity:
 High Intensity Light causes the rate of
photosynthesis to increase
 The rate will increase until it reaches its
saturation point
 At the saturation point, the rate of
photosynthesis remains constant
2. Temperature:
 As temperature increases, so does the rate of
photosynthesis
 Enzymes function at an optimal temperature:
If the temperature is too high or too low,
enzymes will not function properly
 Rate of photosynthesis will slow down or
stop.
3. Water:
 Water is one of the raw materials of
photosynthesis
 A shortage of water can slow or even stop
photosynthesis
 Water stress causes stomata to close,
preventing CO2 from entering the leaf
4. Carbon Dioxide:
 An increase in CO2 concentration causes the
rate of photosynthesis to increase
 More CO2 available means more sugar made
in the light independent reaction
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In hot, dry environments plants maximize
photosynthesis by limiting water loss.
Leaves of plants contain stomata which are
tiny holes in the leaves that release by
products and take in raw materials need for
photosynthesis
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Most plants will close their stomata to
prevent water loss but this limits carbon
dioxide intake
Some plants will only open the stomata
during night
It is a fine balance between receiving the
necessary supplies and preventing water loss.
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If the CO2 concentration in the cell drops
below 50 ppm, the cell begins to undergo
PHOTORESPIRATION which results in the
fixation of oxygen instead of carbon dioxide.
This is a very wasteful process as it produces
a substance that is not useful to the cycle.