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  • In a phototrophic eukaryote, where does photosynthesis take place?

Oxygenic and anoxygenic photosynthesis

For photosynthesis to continue, the electron lost from the reaction center pigment must be replaced. The source of this electron (H 2 A) differentiates the oxygenic photosynthesis of plants and cyanobacteria from anoxygenic photosynthesis carried out by other types of bacterial phototrophs ( [link] ). In oxygenic photosynthesis, H 2 O is split and supplies the electron to the reaction center. Because oxygen is generated as a byproduct and is released, this type of photosynthesis is referred to as oxygenic photosynthesis. However, when other reduced compounds serve as the electron donor, oxygen is not generated; these types of photosynthesis are called anoxygenic photosynthesis. Hydrogen sulfide (H 2 S) or thiosulfate ( S 2 O 3 2− ) can serve as the electron donor, generating elemental sulfur and sulfate ( SO 4 2− ) ions, respectively, as a result.

Photosystems have been classified into two types: photosystem I (PSI) and photosystem II (PSII) ( [link] ). Cyanobacteria and plant chloroplasts have both photosystems, whereas anoxygenic photosynthetic bacteria use only one of the photosystems. Both photosystems are excited by light energy simultaneously. If the cell requires both ATP and NADPH for biosynthesis, then it will carry out noncyclic photophosphorylation . Upon passing of the PSII reaction center electron to the ETS that connects PSII and PSI, the lost electron from the PSII reaction center is replaced by the splitting of water. The excited PSI reaction center electron is used to reduce NADP + to NADPH and is replaced by the electron exiting the ETS. The flow of electrons in this way is called the Z-scheme .

If a cell’s need for ATP is significantly greater than its need for NADPH, it may bypass the production of reducing power through cyclic photophosphorylation . Only PSI is used during cyclic photophosphorylation; the high-energy electron of the PSI reaction center is passed to an ETS carrier and then ultimately returns to the oxidized PSI reaction center pigment, thereby reducing it.

In oxygenic photosynthesis 6 carbon dioxide 12 water and light energy is converted to glucose, 6 oxygen, and 6 water. In anoxygenic photosynthesis carbon dioxide, 2H2A and light energy is converted to a carbohydrate and water. H2A = water, H2S, H2, or other electron donor.
Eukaryotes and cyanobacteria carry out oxygenic photosynthesis, producing oxygen, whereas other bacteria carry out anoxygenic photosynthesis, which does not produce oxygen.
a) Drawing of a thylakoid membrane with proteins. Light strikes PS II which breaks water into ½ O2, 2 H+ and an electron. The electron moves to PO, PQH2, cytochrome, PO, and then to PSI. This is an electron transport chain and as the electron moves, H+ is pumped from the stroma to the thylakoid space. Light Strikes PSI and the electron is excited again; it is then moved to FD and then NADP+ reductase. This produces NADPH from NADP+ and H+. Protons from the inner thylakoid space move out to the stroma through ATP synthase which produces ATP. B) the same diagram but in a graphical format with amount of energy on the Y axis. PSII has an antenna pigment and P680 which absorbs light at 680 nm. This excites the electron (moves it up in the graph). The electron then decreases in energy as it moves from PO to OQHS, to cytochrome, to PO and then to PS I. Light at 700 nm strikes P700 and the electron is excited again. The electron then decreases in energy as it moves from FD to NADP+ reductase to NADPH. Moving from PSII to NADPH is non-cyclic photosynthesis. Cyclic photosynthesis is when the electron moves from PSI back to PS II.
(a) PSI and PSII are found on the thylakoid membrane. The high-energy electron from PSII is passed to an ETS, which generates a proton motive force for ATP synthesis by chemiosmosis, and ultimately replaces the electron lost by the PSI reaction center. The PSI reaction center electron is used to make NADPH. (b) When both ATP and NADPH are required, noncyclic photophosphorylation (in cyanobacteria and plants) provides both. The electron flow described here is referred to as the Z-scheme (shown in yellow in [a]). When the cell’s ATP needs outweigh those for NADPH, cyanobacteria and plants will use only PSI, and its reaction center electron is passed to the ETS to generate a proton motive force used for ATP synthesis.
  • Why would a photosynthetic bacterium have different pigments?

Questions & Answers

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Firomsa Reply
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Lenia Reply
compare and contrast similar structures found in prokaryotic and eukaryotic cells
Lenia
control of microorganisms
ISTEFAZUL Reply
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genital herpes caused by a virus called herpe simplex virus
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classification of gram positive
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gram positive staph is further differentiated on sensitivity test and manitol salt fermentation test while gram positive strep is differentiated on hemolysis pattern
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taxonomy
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facultative anaerobic bavteria gives uniform turdibity in nutrient broth why?
Princess Reply
oils and waxes are not sterilized in autoclave
Princess
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Muhammad
@ MAHI because they can grow all over the media from surface to the bottom as they can utilize oxygen or conduct fermentation in its absence.
Online
2.@MAHI Autoclave uses steam under pressure. The steam cannot penetrate through oil and wax. Thus, dry heat sterilization is preferred than autoclave .
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Nadiya
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Princess
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Princess
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Nadiya
nutrient agar +blood 5ml+ distilled water =blood agar .
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Shimul
because it's a general purpose agar only use for growing bacteria
Richa
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opaleye
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opaleye
antigen is a foreign body that cause activation of antibody?
ASNAKE
Antigen is a toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies.
Shimul
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Luyenu
a science that studies about the drug
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Abdul
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Abdul
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content of their cell wall
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Harley prescott
Vikas
what are the five predisposing factors of opportunistic infections
Asher Reply
1. long term exposure to diseases, that the body immunity weakens.
prosper
2. Nature Of some diseases to weaken body immunity such as, AIDS.
prosper
3. Use of immuno-suppresive drugs.
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Low immune is the major cause eg for kaposis sarcoma
Davismith
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morphological and genetic classification of bacteria
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Bupe
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Sudhir
morphologycal is defined as relating to the branch of biology that deals with the form of living organisms,and with relationship between their structures.
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Nadiya
Hello! How Can Microorganisms Be Isolated From The Skin?.. 5 ways if possible. (briefly)
prosper
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Muhammad
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prosper
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prosper
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prosper
Any question or ideas, Meek?😊
prosper
and if a patient have any blister or abscess on the skin then first cut the blister or abscess. inside material is taking by syringe.
Muhammad
in case of fingernail or toenails simply cut a small piece of nail and culture on the appropriate media at a required temperature and time
Muhammad
Again, thanks Mr. Muhammad! I appreciate the help.
prosper
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Muhammad
what are the media use for skin swab?
Sieh-Mlanwin
blood and macckonkey mostly usededia for skin bacteria
Muhammad
used media*
Muhammad
@ SIEH mostly fungal infection occurs in skin so SDA ( Sabouraud Dextrose Agar) or MEA ( Malt extract agar) are common.
Online
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Microbiologicam source of vitamins
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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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