Physiology 2130 Lecture Notes - Lecture 2: Fluid Compartments, Extracellular Fluid, Phospholipid

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5 Feb 2013
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Physiology Lecture 2 Cell Membrane
Function of the Cell Membrane
o The composition of the interstitial fluid and plasma are approximately the same
o The composition of intracellular and extracellular fluid are dramatically different
o Differences are possible because the intracellular fluid is separated from the interstitial
fluid by a cell membrane
o Cell membrane is selectively permeable and contains transport mechanisms which
favour the ion distribution
o Important to maintain the ion gradients
o Selective for different ions and molecules
o Controls what goes in and out of cell
Structure
o Fatty acid chains of the phospholipid are hydrophobic
Represent the major permeability barrier to water and water-soluble
substances such as ions, glucose, urea, and most other molecules found in living
organisms
o Fat-soluble substances such as oxygen, alcohol, and steroid hormones can penetrate
this portion of the membrane
o Phosphate Head hydrophilic, polar, stick towards the outside of the cell
o 2 Fatty Acid Chain Tails hydrophobic, non-polar, make up the core of the cell
membrane
o Transmembrane Protein help transport big ions and other things inside and out of the
cell
o Cholesterol affects fluidity of membrane
o Glycoprotein always external, a carbohydrate stuck to a protein
o Glycolipid carbohydrate with 2 lipid tails
o External proteins proteins on the outside of the sell