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Hej, er der nogen der ville give sig 5 minutter til at hjælpe mig med at forstå hvad de siger i denne tekst? Jeg forstår den ikke helt. Jeg håber i ville hjælpe. På forhånd mange tak.
In bacterial photosynthesis, a single photosystem is involved. When an electron is energized by absorption a light, it is ejected from the photosystem reaction center. The electron then passes to ferredoxin, and then down through the cytochrome b6-f complex, plastocyanin (pC), and finally back to the reaction center. The energy released during this electron transport generates a proton gradient, which is used to produce ATP. Since the excited electron returns to the reaction center, this mechanism for making ATP is called Cyclic photophosphorylation. The reducing power needed for biosynthesis is not generated in the process of cyclic photophosphorylation. Plants and cyanobacteria utilize two photo systems, which work sequentially to produce both energy and reducing power. First, a photon of light ejects a high-energy electron from photosystem 2. The electron lost from photosystem 2 does not return to photosystem 2, but is replaced by an electron generated from the splitting of water and the production of oxygen. The electron then travels from the excited reaction center of photosystem 2 to plastoquinone, to the b6-f complex, to plastocyanin and finally to the reaction center of photosystem 1. This electron transport system generates a proton motive that is used to produce ATP. Since the excited electron does not return to photosystem 2, this mechanism for making ATP is called noncyclic photophophorylation. When photosystem 1 absorbs a photon of light, it ejects a high-energy electron. The energy from this light absorption is used to generate reducing power in the form of NADPH. The ejected electron is replaced by an electron from photosystem 2.
Svar #1
27. august 2008 af Da-ted (Slettet)
I bakteriel fotosyntese er et enkelt fotosystem (proteinklump eller enzym der reducerer molekyler vha. lys) involveret. Når en elektron bliver ladet af absorberet sollys bliver det skudt ud fra fotosystemets reaktionscenter (fagterm igen) Elektronen passerer derefter til ferredoxin og derefter gennem zytochromet (hemoprotein til elektrontransp) b6-f kompleks plastocyanin (pC) og endelig tilbage til centret. Energien skaber et elektrokemisk potientiale hvilket bliver brugt til at producere atp. Idet elektronen vender tilbage til centret hedder processen Cyklisk fotofosforylation (af ATP). Der bliver ikke genereret den nødvendige energi for biosynthese i denne process. Planter og cyanobakterier benytter to foto-systemer efter hinanden hvilket både generer atp og energi til biosynthese.
Først udsender en proton en højenergis elektron fra fotosystem 2. Elektronen kommer ikke tilbage men bliver erstattet af en elektron der er skabt ved brydnigenn af bindinger i vand ved produktionen af oxygen. Elektronen rejser derefter videre fra fotosystem 2's eksiterede reaktionscenter gennem plastoquinone (transport) til b6-f komplekset til pastocyanin og derefter til sidst til reaktioncentret for fotosystem 1. Elektrontransportsystemet genererer et protonpotientiale der brugestil at producere ATP. Idet elektronen ikke vender tilbage til sit reaktionscenter kaldes det for en ikke-cyklisk ATP-fotofosforlationsprocess.
Når fotosystem 1 absorberer en foton udsender den en højenergis elektron. Energien fra denne absorbtion bruges til at generere "reducing power" i form a NADPH. Elektronen bliver erstattet af en elektron fra fotosystem 2.
Ved ikke helt hvordan jeg skal oversætte reducing power.. Engelsk fagterm der lyder ekstremt dumt på dansk..Tjek med biologi
Svar #2
27. august 2008 af Signesp (Slettet)
Er det det samme som der står her?
In plants, photosynthesis occurs in specialized organelles called chloroplasts. The internal membranes of chloroplats are organized into sacs called thylakoids. Surrounding the thylakoid membrane system is a semiliquid substance called stroma. Photosynthetic pigments are clustered together to form photosystems. When a photon of light strikes the reaction center of photosystem 2, it excites an electron. Two water molecules bind to an enzyme at the reaction center. This enzyme splits the water and uses the electrons from the water to replace the electrons removed from the reaction center. Oxygen is produced in this process. The primary electron acceptor for the light-energized electrons leaving photosystem 2 is plastoquinone. The reduced plastquinone passes the excited electrons to a proton pump embedded in the membrane called the b6-f complex. Arrival of the energetic electrons causes the b6-f complex to pump protons from the stroma into the thylakoid space, thereby generating a proton gradient across the membrane. Because the thylakoid membrane is impermeable to protons, the protons in the stroma must pass through the channels provided by ATP synthase. As protons pass through, ADP is phosphorylated to ATP and released into the stroma. This process for making ATP is referred to as photophosphorylation. When photosystem I absorbs a photon of light, its reaction center passed high-energy electrons to ferredoxin. The enzyme NADP reductase then transfers the electrons to NADP to form NADPH. Electrons lost from photosystem I are replaced by electrons generated from photosystem 2. A small protein called plastocyanin (pC) then carries the electrons from the b6-f complex to photosystem 1.
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