SBI4U – Metabolic Processes
106736570
Date: ___________________________
Photosynthesis
Introduction to Photosynthesis
There are two main stages in photosynthesis
____________________________________________
____________________________________________
The first stage traps _____________________________ in the bonds of the energy
carrier molecules _____________ and ______________
The second stage uses this stored chemical energy to synthesize ______________
and _____________________
The ____________________ is also known as
the “________________________” Reactions,
and they occur in the __________________
________________ of the chloroplasts
The ___________________ is also known as
the “_________________________” Reactions
and they occur in the ________________
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Historical Background
In early experiments on photosynthesis, Joseph Priestley found that a green plant
sealed in a jar with a candle or a mouse could
“______________” the air in the jar
He was the first to observe the
_______________ of plants
Van Helmont did an experiment in which he
weighed a small tree, the soil in the pot in which
the tree was planted and the water given to the
tree over a five year period
He found that the tree changed its __________
significantly over the five years while the mass
of the _____________________________
Van Helmont concluded that the mass gained
did not come from the ___________, but rather from the
______________________________
Pigments
Pigments are molecules that can absorb certain _______________ of ___________
The primary pigment of
photosynthesis is chlorophyll
Chlorophyll is green in colour
because it _____________ green
light while it ______________ red
and blue colours
Additional pigments called
__________________ pigments
absorb most colours of the visible
spectrum to some extent
Most leaves appear green because chlorophyll is much more ________________
than the accessory pigments
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Chlorophyll ______________ in short daylight allowing the colours of the accessory
pigments to become visible in the fall
Chlorophyll
Although there is only a slight difference in the ___________________________ of
Chlorophyll A and B, Chlorophyll A is located in the __________________________
where radiant energy is transferred for the production of energy carrier molecules
The characteristics chemical structure of chlorophyll is a series of alternating
___________ and ______________ bonds
The electrons of the double bonds are held _______________________ than the
electrons of the single bonds
Light energy is ________________ by the loosely held electrons, freeing them from
the bond and enabling them to enter a series of reactions similar _______________
_________________________ of aerobic respiration
Photosystems
Some chlorophyll and accessory pigments
are grouped into two types of light gathering
complexes called ____________________
___________ (PSII) and ______________
____________ (PSI)
These light gathering complexes are embedded in the __________________
____________ of the chloroplast
Photosystem II is also called _________, because the reaction center of this type of
photosystem best absorbs light photons at a wavelength of ____________
Photosystem I is also referred to as ___________ because the reaction center of
this type of photosystem best absorbs light photons at a wavelength of
____________
The photons absorbed in Photosystem II have ___________________ because the
___________________ of light have the higher energy
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Each photosystem is composed of several hundred __________________________
molecules
They are called _______________________________ because they collect and
channel energy to the ___________________________
Accessory pigments can be molecules of
chlorophyll A and a variety of other
accessory pigments such as:
_________________________
_________________________
_________________________
_________________________
_________________________
These other types of pigment molecules help absorb some light at wavelengths not
absorbed by chlorophyll
Photosynthesis is broken into two reactions
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Light Dependent Stage (Photo Stage)
When a _______________ of light energy eventually reaches the chlorophyll A
molecule at the __________________, ________ electrons from the chlorophyll A
molecule are bounced out of the _________________
This means that the chlorophyll molecule has been ___________________
The energized electrons are quickly absorbed by
an electron acceptor called “____” embedded in
the ____________________ membrane
The electrons lost by the chlorophyll A molecule in the reaction center of the
Photosystem II are immediately ___________________ with two electrons released
in the _____________________ or splitting of
one molecule of water
In addition to the two electrons, photolysis
also produces two _______ and _______ that
is released in to the atmosphere
The two electrons from Photosystem II that were absorbed by electron acceptor “Q”
are then transferred to ___________________ and on to several other molecules in
a series of ___________________________ reactions
This electron transport chain is very similar to that found in mitochondria
The production of ATP is similar to that in
_______________________ in that H+ are
pumped into the ______________________
and large electrochemical gradient is
established
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At the end of the first electron transport chain, the pair of electrons move to
_____________________, where they again become energized by another
______________ of light
The newly energized electrons are quickly passed to _________________ and then
they go on to combine with NADP+ and H+ to produce ______________
The ATP and NADPH molecules then move to the ______________ where they are
used to power the _______________________________
Light Independent Stage
Sometimes known as the _____________________ or the ____________________
This is the ____________________ stage
The role of the dark reactions is to fix ___________________ into ______________
using ___________ energy transformed from ___________ energy in the thylakoids
The dark reactions occur in the stroma of the chloroplasts
Although the dark reactions do not require _______________ or use ___________,
it cannot take place in the absence of light because it needs _______________ from
the light reaction
Although _______________ is the primary product of photosynthesis, more complex
___________________ as well as ____________ and _____________ can be
synthesized as byproducts of the dark reactions
The Calvin Cycle
The Calvin Cycle (or C3 Cycle) begins with a molecule of _____________________
________________ and results in the
production of one molecule of ____________
3 molecules of ________________________
are reacted with 3 molecules of ________,
which are then immediately broken into 6
molecules of _________________________
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Each of the six 3-phosphoglycerates is phosphorylated by ____________ into six
___________________________ which are then converted to _________________
_______________ using NADPH as energy
One glyceraldehyde -3-phosphate is removed from the cycle, leaving 5 molecules of
glyceraldehyde-3-phosphate, which are converted to _________________________
The three ribulose-5-phosphates are then _________________________________
back to ____________________________________ to start the cycle again
Each turn of the cycle “fixes” one molecule of CO2
Therefore, 6 turns of the cycle are necessary to fix the carbon in one molecule of
glucose since glucose has ___________________
A total of 18 molecules of ATP and 12 molecules of NADPH are provided as energy
by the light reaction
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