BIOLOGY 173 Lecture Notes - Lecture 7: Fluid Mosaic Model, Surface 3, Membrane Transport
15 Sep 2016
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The plasma membrane = cell membrane = plasmalemma. Structure of the plasma membrane: components and their function: lipids compose about 42% of the membrane by weight. Phospholipid: hydrophilic head containing glycerol and phosphate, hydrophobic tail containing two fatty acids, arrangement: bilayer hydrophilic heads on the outsides and hydrophobic tails on the inside, function: boundary, barrier, separates intracellular from extracellular, cholesterol too! Stiffens membrane: proteins compose about 55% of the membrane by weight. Two types : integral embedded, penetrates, spans membrane, peripheral loosely associate with the inner or outer surface, carbohydrates composes about 3% of the membrane by weight. It is called fluid because the components of the membrane move. It is refereed to mosaic because of the proteins embedded in the lipids that make patterns. Selectively permeable barrier: permits passage of some substances but not all. Membrane transport (how things get in and out of the cell) Major categories of transport mechanisms: diffusion: (passive)
