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Cards In This Set
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When chlorophyll absorbs light energy, its electrons are excited to high energy levels. the energetic chloropyll electrons are transferred o what?
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Othere electron acceptors in the chloroplast membrane
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One the excited electrons leave the chlorophyll, what replaces them?
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Electrons from water (water is oxidized), which produces oxygen gas, and also later on, reduces Co2 and makes ATP
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What is the independent variable of this lab
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The amount of chloroplasts added to the reaction mixture
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What is the dependent variable of this lab
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The rate at which water is oxidized using indirect measure (oxidation of water is coupled by the reduction of DPIP, when DPIP is reduced it looses its blue color, making it clear)
so basically the rate at which DPIP becomes clear is the rate at which water is oxidized) |
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What did we do to prepare the chloroplasts?
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Blend spinach leaves with NaCl buffer, so that pH is not a variable in our spectromoeter measurements of the reduction of DPIP/ oxidation of water rate)
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When did we add the cholorplasts to the reaction solutions?
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Last!
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At what wavelength did we measure the absorbance?
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600nm, orange light, almost red
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The more cholorplast added, the what the rate of oxidation of water/ reduction of DPIP?
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The more chloroplasts added the higher the rate of ox of water/redofDPIP
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Is the rate effected by heat of the lamp or by light itself?
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Light, heat has no effect
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Why
do you suppose a buffer was used for the isolation and function assessment of
chloroplasts?
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A
buffer was used to control the pH. This
is necessary to maintain a constant external environment for the chloroplasts,
which helps them survive the experimental procedures. Also, many biological reactions are sensitive
to pH; the buffer held the pH steady to eliminate changes in pH as an
experimental variable.
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Why
was bisulfite added to the "blank" tubes in your experiments with
chloroplast function?
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The
bisulfite reduced the DPIP, so the blank had everything in it that the
experimental tube had, except the blue color.
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In the experiment where the amount
of chloroplasts was varied, what do your results show about chloroplast
function?
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The
more chloroplasts, the faster the dye reduction, as shown by the data when
graphed. (See graphs above.) The direct relationship between rate of DPIP
reduction and amount of chloroplasts indicates the dependence of water
oxidation/dye reduction on active chloroplasts.
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In
the experiment on the effect of illumination on chloroplast function, why was
it necessary to have the light on and positioned above the tube darkened with
aluminum foil, since the aluminum foil should have prevented any light from
reaching the chloroplasts?
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To
control for the effect of heat. Heat,
instead of light, could have been the factor that drove the oxidation of water
and/or the reduction of DPIP.
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In
the reaction you have been studying in this laboratory, where are the electrons
that reduce the DPIP coming from?
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The electrons originate from water.
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Where
do these electrons normally end up when the full process of photosynthesis is occurring? How important is this for the overall process
of photosynthesis?
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The
electrons are normally given to CO2,
thereby reducing it. Reduction of CO2 to sugar is the essence of
photosynthesis.
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