Fandom

VroniPlag Wiki

Ry/Fragment 021 01

< Ry

31.348Seiten in
diesem Wiki
Seite hinzufügen
Diskussion0 Share

Störung durch Adblocker erkannt!


Wikia ist eine gebührenfreie Seite, die sich durch Werbung finanziert. Benutzer, die Adblocker einsetzen, haben eine modifizierte Ansicht der Seite.

Wikia ist nicht verfügbar, wenn du weitere Modifikationen in dem Adblocker-Programm gemacht hast. Wenn du sie entfernst, dann wird die Seite ohne Probleme geladen.


Typus
KomplettPlagiat
Bearbeiter
SleepyHollow02
Gesichtet
Yes.png
Untersuchte Arbeit:
Seite: 21, Zeilen: 1 ff. (entire page)
Quelle: Anézo 2003
Seite(n): 34 f., Zeilen: 34: 22 ff.; 35: 1 ff.
Hydrogen bonding and poor hydration of the PE headgroups result in a stabilization of the gel state relative to the liquid crystalline state. For PC, the possibility of direct hydrogen bonds between the headgroups is missing, so that the PC headgroups interact much more strongly with water. This increases the hydration of the bilayers, modifies its structure and lowers the gel-fluid transition.

Effect of phospholipids mixtures. Mixing phospholipids together alters the phase behavior of each phospholipid component in a complex way. The study of lipid mixtures is of great interest since biological membranes contain a variety of lipid species. The fact that biomembranes are generally in a lamellar liquid crystalline phase under physiological temperatures shows that a well-defined balance in the lipid composition is necessary to maintain such a fluid morphology.

Effect of cholesterol. Cholesterol tends to fluidize the gel phase Lβ and to order the lamellar liquid crystalline phase Lα, thereby broadening or even eliminating the transition between the two phases. Cholesterol can induce a liquid crystalline state in phospholipids that would otherwise adopt a gel state, enhancing thus the stability of fluid bilayers. However, maintaining a fluid state in biological membranes is likely not the major role of cholesterol in cell biology. Most plasma membranes would be indeed in a fluid state at 37oC without cholesterol. The introduction of a double bond in the hydrocarbon chains of membrane phospholipids, for example, would be sufficient to keep the bilayers in a liquid crystalline state [10]. Cholesterol is, nonetheless, essential for the normal growth and functioning of cells (e.g. by modulating the function of the membrane proteins through direct binding to sterol-specific sites on membrane proteins). The ordering effect of cholesterol observed in fluid bilayers can be explained by the rigid structure of cholesterol. The portion of the phospholipid hydrocarbon chains encountering the rigid steroid nucleus is indeed hindered in its motion and trans-gauche isomerization about the carbon-carbon bonds is diminished. The effects of cholesterol on the phospholipid phase behavior are however much more complex than described above and are strongly [dependent on the cholesterol concentration.]


10. Yeagle, P. L. The Membranes of Cells, 2nd ed.; Academic Press: San Diego, 1993.

Hydrogen bonding and poor hydration of the PE headgroups result in a stabilization of the gel state relative to the liquid crystalline state. For PC, the possibility of direct hydrogen bonds between the headgroups is missing, so that the PC headgroups interact much more strongly with water. This increases the hydration of the bilayer, modifies its structure, and lowers the gel-fluid transition.

Effect of phospholipid mixtures Mixing phospholipids together alters the phase behavior of each phospholipid component in a complex way. The study of lipid mixtures is of great interest since biological membranes contain a variety of lipid species. The fact that biomembranes are generally in a lamellar liquid crystalline phase under physiological temperatures shows that a well-defined balance in the lipid composition is necessary to maintain such a fluid morphology.

[page 35:]

Effect of cholesterol Cholesterol tends to fluidize the gel phase Lβ and to order the lamellar liquid crystalline phase Lα, thereby broadening or even eliminating the transition between the two phases. Cholesterol can induce a liquid crystalline state in phospholipids that would otherwise adopt a gel state, enhancing thus the stability of fluid bilayers. However, maintaining a fluid state in biological membranes is likely not the major role of cholesterol in cell biology. Most plasma membranes would be indeed in a fluid state at 37oC without cholesterol.

The introduction of a double bond in the hydrocarbon chains of membrane phospholipids, for example, would be sufficient to keep the bilayer in a liquid crystalline state [2]. Cholesterol is, nonetheless, essential for the normal growth and functioning of cells (e.g. by modulating the function of membrane proteins through direct binding to sterol-specific sites on membrane proteins). The ordering effect of cholesterol observed in fluid bilayers can be explained by the rigid structure of cholesterol. The portion of the phospholipid hydrocarbon chains encountering the rigid steroid nucleus is indeed hindered in its motion and trans-gauche isomerization about the carbon-carbon bonds is diminished. The effects of cholesterol on the phospholipid phase behavior are however much more complex than described above and are strongly dependent on the cholesterol concentration.


[2] P. L. Yeagle. The Membranes of Cells. Academic Press, San Diego, second edition, 1993.

Anmerkungen

The source is not given.

Sichter
(SleepyHollow02) Schumann

Auch bei Fandom

Zufälliges Wiki