2. Lose a little bit of energy to a sub excited state, and then you can lose the
remaining energy as fluorescence light. This red light is different from the red
light that it absorbs in the beginning. Fluorescence light has longer
wavelength, slightly lower energy because some of the energy has lost as heat
from the excited state
3. You can do work: trapping energy to do work. The work is photochemistry.
Using the light to change the structure of a pigment.
4. Transfer the energy of the excited state of the pigment to a neighbouring
g. Reason(s) why relative fluorescence is different in isolated chlorophyll vs. intact
cells when exposed to light.
Fluorescence is higher with isolated chlorophyll. There is less fluorescence in the cell sample
(intact cell) because the cell requires a lot of energy for it to run the cell processes it needs to
function properly. Therefore, the energy produced by the excitation could be used by essential
molecules and cell organelles to perform these processes. The energy can also be transferred to the
reaction center to drive photochemistry as part of photosynthesis. It is possible that the cell has
developed an evolutionary mechanism which help utilize light energy by minimizing energy loss
and the amount of fluorescence give off. In the isolated chlorophyll, there is no pathway for the
energy produced to be utilized so it is released via fluorescence. Since none of the energy is being
utilized by other processes like in the cell, most of the energy is released as fluorescence,
producing a higher amount of fluorescence than in the cell.
h. What accounts for the fact that chlorophyll is green in colour
It is because there is no green excited state. There isn’t excited state between red and blue photon
absorption. If there was then the chlorophyll will be able to absorb green light. Green photons are
just lost so chlorophyll cannot absorb them, so the photon is either reflected or transmitted through
i. Quantitative relationship between photons and excited electrons.
One photon can excite one electron: one to one equivalency.
j. Relationship between energy of photon and energy required to excite electrons in
order for photons to be absorbed.
For the energy to absorb, to trap the photon, the energy that’s in the photon,
whatever that energy is, must match the energy required to get from the ground
state to the excited state.
k. General structure of photosystem.
Photosystem comprised with 2 parts: antenna, protein and chlorophyll that is
individually bound to the protein antenna surrounds the reaction center in the
l. Similarities and differences of the light capturing and photochemistry of
phototransduction (retinal) vs. photosynthesis (chlorophyll).
Similarities of light capturing: both absorbs photons of light in visible light
Similarities of photochemistry:
Differences of light capturing: in photosynthesis, you want to capture as much
light as possible whereas in photoreceptor, the rods and cones harvest light as
Differences of photochemistry: in phototransduction, this event takes place in
photoreceptor, the photochemical event is called the isomerization of retinal. In
photosynthesis, the structural unit of light capture is called photosystem. In
phototransduction, there is a change of the configuration of cis-tran retinal. When