phospholipids are known to reside in the cells membranes- i say membranes because this includes the plasma membrane, as well as nuclear membrane, mitochondrial outer/inner membranes, lysosomal membrane, and peroxisomal membrane. There is of course a reason for this: the polar, charged head groups (ex. the "serine" in phosphatidyl serine) prefer to interact with aqueous media, as do all charged molecules. The glycerol and fatty acyl groups are highly hydrophobic, meaning that they prefer to high from water. If you put phospholipids in water, what you'll see is that they spontaneously form either "micelles" or a"lipid bilayer" to keep delta G negative- ie. its highly favorable, and no energy is required to carry this out.
also important to consider is that the charged head group on almost all phospholipids is important in signaling and communication between and within cells. Having these head groups sticking out of a membrane, either on the cytoplasmic face or extracellular face, allow them to perform this task well.
2007-09-26 14:50:42
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answer #3
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answered by GUIDO 4
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