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Many photosynthetic organisms have a mixture of pigments; using them, the organism can absorb energy from a wider range of wavelengths. Not all photosynthetic organisms have full access to sunlight. Some organisms grow underwater where light intensity and quality decrease and change with depth. Other organisms grow in competition for light. Plants on the rainforest floor must be able to absorb any bit of light that comes through, because the taller trees absorb most of the sunlight and scatter the remaining solar radiation ( [link] ).

The photo shows undergrowth in a forest.
Plants that commonly grow in the shade have adapted to low levels of light by changing the relative concentrations of their chlorophyll pigments. (credit: Jason Hollinger)

When studying a photosynthetic organism, scientists can determine the types of pigments present by generating absorption spectra. An instrument called a spectrophotometer    can differentiate which wavelengths of light a substance can absorb. Spectrophotometers measure transmitted light and compute from it the absorption. By extracting pigments from leaves and placing these samples into a spectrophotometer, scientists can identify which wavelengths of light an organism can absorb. Additional methods for the identification of plant pigments include various types of chromatography that separate the pigments by their relative affinities to solid and mobile phases.

What happens when a compound absorbs a photon of light?

When a compound absorbs a photon of light, the compound becomes "excited", in the sense that it has this extra energy. This is illustrated in figure 7 schematically. The compound has some ground state, it absorbs a photon and now contains this excess absorbed energy and is considered "excited". The question because what does the compound do with this excess absorbed energy and how does it get back to its "ground" state.

Energy diagram (energy story) of what happens to a molecule that absorbs a photon of light.

What does the excited atom or molecule do to return to its ground state. The energy in this molecule can then be dissipated in a variety of ways as the excited electron decays back to its ground state. There are four possible outcomes, which are schematically diagrammed in Figure 8 below. These energy options are:

  1. The energy can be dissipated as heat.
  2. The energy can be dissipated as fluorescence as the e - returns to a lower orbital.
  3. The energy can be transferred by resonance to a neighboring molecule as the e - returns to a lower orbital.
  4. The energy can change the reduction potential such that it can become an e - donor. Linking this excited e - donor to a proper e - acceptor can lead to the transduction of chemical energy this will be discussed in quite some detail in a later video and in lecture. For now lets just leave this as the ability of the excited molecule be converted into chemical work. In other words the excited state can be used in red/ox reactions.

As the excited electron decays back to its original orbit, the energy can be released in a variety of ways. While many of the antenna or auxiliary pigments absorb light energy and transfer it to the reaction center (as depicted in option III in figure 8) it is what happens at the reaction center that we are most concerned with (option IV in figure 8). Here a chlorophyll or bacteriochlorophyll molecule absorbs the energy and an electron is excited. This energy transfer is sufficient to allow the reaction center to donate the electron in a red/ox reaction to a second molecule. This initiates the photophosphorylation electron transport reactions. The result is an oxidized reaction center that must now be reduced in order to start the process again. How this happens is the basis of electron flow in photophosphorylation and will be described in detail below.

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Good
what does post-translational control refer to?
Teresa Reply
Bioremediation includes
Rachel Reply

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Source:  OpenStax, Ucd bis2a intro to biology v1.2. OpenStax CNX. Sep 22, 2015 Download for free at https://legacy.cnx.org/content/col11890/1.1
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