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Photophosphorylation a brief synopsis

Photophosphorylation is the process of converting light into chemical energy, ATP and NADPH. Photosynthesis is the integration of these light-reactions driving the reduction of CO 2 to sugars, specifically Glyceraldehyde-3-Phosphate, a triose. In this module we will focus on the first part of photosynthesis, the light-reactions or the generation of ATP and NADPH from light.

First and foremost it is important to realize that photophosphorylation and photosynthesis are very ancient sets of reactions. When we think of photosynthesis we mainly think of green plants; taking up CO 2 and giving off O 2 . But this is a special, and from an evolutionary perspective, relatively new form of photophosphorylation. While extremely efficient and complicated, oxygenic photophosphorylation , the form of photophosphorylation that produces O 2 as a product, is only part of the picture of the evolution of photophosphorylation.

Photophosphorylation has its roots in the anaerobic world, between 3 billion and 1.5 billion years ago, when life was abundant in the absence of molecular oxygen. Photophosphorylation probably evolved relatively shortly after electron transport chains and anaerobic respiration began to provide metabolic diversity. Think of photophosphorylation this way: it is simply a form of an electron transport chain. The major difference is that instead of electrons being donated by a very strong reducing compound, such as NADH, light energy is used to "energize" an electron into a "high energy state". This "energized" electron can be donated to an electron transport chain, and as it decays, that is, as it passes from one electron carrier to another via red/ox reactions protons are pumped across a membrane. The pumping of these protons across a membrane leads to the generation of a PMF, which in turn results in the production of ATP. If enough light energy or photons can be absorbed and transferred to electrons, and if those electrons can have a lower (that is a more negative) reduction potential than NADP/NADPH, then they can be used reduce NADP to form NADPH. Therefore, photophosphorylation requires a compound that can absorb light energy or photons, use that energy to excite an electron and then donate that excited electron to NADPH. That compound is chlorophyll or bacteriochlorophyll. The final piece of the photophosporylation story is finding something to reduce the oxidized bacteriochlorophyll, under anaerobic conditions, reduced sulfur compounds such as SH 2 and even elemental S 0 are excellent electron donors (look at the redox tower provided in figure 9 to see more potential electron donors).

These early, simple anoxygenic photophosphorylation pathways could either make NADPH, in a process called noncyclic photophosphorylation or ATP, in a processes called cyclic photophosphorylation per donated electron. At some point, about 1.5 billion years ago, a chlorophyll molecule evolved that when oxidized (when a photon of light was absorbed and transferred to the electron which is ejected) had a higher (more positive) reduction potential than O 2 . Which meant that the oxidized form of chlorophyll could be reduced by water and generate molecular oxygen. That event changed the shape of the planet for ever. That event, the great oxygen event now begins to accumulate molecular oxygen, a toxic, highly corrosive and reactive compound, into the environment and life on this planet would change forever.

Questions & Answers

what is microbiologist
Muhammad Reply
what is errata
Muhammad
is the branch of biology that deals with the study of microorganisms.
Ntefuni Reply
What is microbiology
Mercy Reply
studies of microbes
Louisiaste
when we takee the specimen which lumbar,spin,
Ziyad Reply
How bacteria create energy to survive?
Muhamad Reply
Bacteria doesn't produce energy they are dependent upon their substrate in case of lack of nutrients they are able to make spores which helps them to sustain in harsh environments
_Adnan
But not all bacteria make spores, l mean Eukaryotic cells have Mitochondria which acts as powerhouse for them, since bacteria don't have it, what is the substitution for it?
Muhamad
they make spores
Louisiaste
what is sporadic nd endemic, epidemic
Aminu Reply
the significance of food webs for disease transmission
Abreham
food webs brings about an infection as an individual depends on number of diseased foods or carriers dully.
Mark
explain assimilatory nitrate reduction
Esinniobiwa Reply
Assimilatory nitrate reduction is a process that occurs in some microorganisms, such as bacteria and archaea, in which nitrate (NO3-) is reduced to nitrite (NO2-), and then further reduced to ammonia (NH3).
Elkana
This process is called assimilatory nitrate reduction because the nitrogen that is produced is incorporated in the cells of microorganisms where it can be used in the synthesis of amino acids and other nitrogen products
Elkana
Examples of thermophilic organisms
Shu Reply
Give Examples of thermophilic organisms
Shu
advantages of normal Flora to the host
Micheal Reply
Prevent foreign microbes to the host
Abubakar
they provide healthier benefits to their hosts
ayesha
They are friends to host only when Host immune system is strong and become enemies when the host immune system is weakened . very bad relationship!
Mark
what is cell
faisal Reply
cell is the smallest unit of life
Fauziya
cell is the smallest unit of life
Akanni
ok
Innocent
cell is the structural and functional unit of life
Hasan
is the fundamental units of Life
Musa
what are emergency diseases
Micheal Reply
There are nothing like emergency disease but there are some common medical emergency which can occur simultaneously like Bleeding,heart attack,Breathing difficulties,severe pain heart stock.Hope you will get my point .Have a nice day ❣️
_Adnan
define infection ,prevention and control
Innocent
I think infection prevention and control is the avoidance of all things we do that gives out break of infections and promotion of health practices that promote life
Lubega
Heyy Lubega hussein where are u from?
_Adnan
en français
Adama
which site have a normal flora
ESTHER Reply
Many sites of the body have it Skin Nasal cavity Oral cavity Gastro intestinal tract
Safaa
skin
Asiina
skin,Oral,Nasal,GIt
Sadik
How can Commensal can Bacteria change into pathogen?
Sadik
How can Commensal Bacteria change into pathogen?
Sadik
all
Tesfaye
by fussion
Asiina
what are the advantages of normal Flora to the host
Micheal
what are the ways of control and prevention of nosocomial infection in the hospital
Micheal
what is inflammation
Shelly Reply
part of a tissue or an organ being wounded or bruised.
Wilfred
what term is used to name and classify microorganisms?
Micheal Reply
Binomial nomenclature
adeolu
what's microbiome?
john Reply
Microbiology is the scientific study of microorganisms
Ibra
the microorganisms in a particular environment (including the body or a part of the body).
Ibra
describe the bacterial cell
Akello
The biggest populations of microbes reside in the gut.other popular habitats include the skin genitals.The microbial cells and their genetic material ,the microbiome ,live with human from birth .
Zahreen
can agriculture be integrated into biology
David
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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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