Thylakoid: Difference between revisions
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Inside [[plant]] [[Cell (biology)|cells]] and other [[Eukaryote|eukaryotic]] cells that perform [[photosynthesis]], tiny, [[bacteria]]-sized [[organelle]]s, called [[chloroplast]]s, contain, within the inner membrane of their dual membrane structure, an extensive system of single-membrane-bound disk-shaped sacs called '''thylakoids''', their interior spaces (lumens) interconnected, their membranes housing the pigment molecules that absorb the [[energy]] of [[photon]]s of particular frequencies emitted by the sun, an event that initiates the physico-chemical sequence of steps culminating in the products of photosynthesis.<ref>[http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/Chloroplasts.html Chloroplasts]. | Additional information about chloroplasts and thylakoids.</ref> Thylakoids | Inside [[plant]] [[Cell (biology)|cells]] and other [[Eukaryote|eukaryotic]] cells that perform [[photosynthesis]], tiny, [[bacteria]]-sized [[organelle]]s, called [[chloroplast]]s, contain, within the inner membrane of their dual membrane structure, an extensive system of single-membrane-bound disk-shaped sacs called '''thylakoids''', their interior spaces (lumens) interconnected, their membranes housing the pigment molecules that absorb the [[energy]] of [[photon]]s of particular frequencies emitted by the sun, an event that initiates the physico-chemical sequence of steps culminating in the products of photosynthesis.<ref>[http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/Chloroplasts.html Chloroplasts]. | Additional information about chloroplasts and thylakoids.</ref> Thylakoids are bathed in a semifluid matrix called the [[stroma]]. | ||
In [[Prokayote|prokaryotic]] cells that carry out photosynthesis (e.g., [[cyanobacteria]]), the thylakoid membranes are not contained within chloroplasts, but are layered in the cytoplasm.<ref name=barton2005>Barton L. (2005) [http://dx.doi.org/10.1007/b138652 ''Structural and functional relationships in prokaryotes'']. New York: Springer, ISBN 9780387271255. | Discusses thylakoids in cyanobacteria</ref> | In [[Prokayote|prokaryotic]] cells that carry out photosynthesis (e.g., [[cyanobacteria]]), the thylakoid membranes are not contained within chloroplasts, but are layered in the cytoplasm.<ref name=barton2005>Barton L. (2005) [http://dx.doi.org/10.1007/b138652 ''Structural and functional relationships in prokaryotes'']. New York: Springer, ISBN 9780387271255. | Discusses thylakoids in cyanobacteria</ref> | ||
Revision as of 16:57, 18 November 2010
Inside plant cells and other eukaryotic cells that perform photosynthesis, tiny, bacteria-sized organelles, called chloroplasts, contain, within the inner membrane of their dual membrane structure, an extensive system of single-membrane-bound disk-shaped sacs called thylakoids, their interior spaces (lumens) interconnected, their membranes housing the pigment molecules that absorb the energy of photons of particular frequencies emitted by the sun, an event that initiates the physico-chemical sequence of steps culminating in the products of photosynthesis.[1] Thylakoids are bathed in a semifluid matrix called the stroma.
In prokaryotic cells that carry out photosynthesis (e.g., cyanobacteria), the thylakoid membranes are not contained within chloroplasts, but are layered in the cytoplasm.[2]
In general terms, the photosynthetic process enables the energy of photons radiated from the sun to energize electrons in special photon-absorbing pigment molecules embedded in the thylakoid membranes, electrons ultimately supplied by the splitting of water molecules in a reaction that also converts water's oxygen atoms to molecular oxygen for release into the atmosphere and for use by the plant.
The thylakoid membranes also contain molecular clusters that transfer the energy of the energized electrons to energy-carrier molecules, the energy therein used in metabolic reactions in the stroma to synthesize organic compounds using the inorganic carbon compound, carbon dioxide, as the carbon source starting material.[3]
Schematic of a chloroplast: 1. outer membrane; 2. intermembrane space; 3. inner membrane (1+2+3: envelope); 4. [stroma (aqueous fluid); 5. thylakoid lumen (inside of thylakoid); 6. thylakoid membrane; 7. granum (stack of thylakoids); 8. thylakoid (lamella); 9. Starch; 10. Ribosome; 11. plastidial DNA; 12. plastoglobule (drop of lipids).
The Internet has numerous images of thylakoids of particular instructive value. You will find links to those images on the Gallery subpage.
References
- ↑ Chloroplasts. | Additional information about chloroplasts and thylakoids.
- ↑ Barton L. (2005) Structural and functional relationships in prokaryotes. New York: Springer, ISBN 9780387271255. | Discusses thylakoids in cyanobacteria
- ↑ Thylakoid. FT Exploring. Where and how photosynthesis occurs in a typical leaf.