BIOL 1201 : Exam 2
Document Summary
The problem a cell and its environment: the interior of a cell is different than its environment, how to defend the internal environment but still communicate with the external environment, transport materials across the barrier. Integral membrane proteins: amphipathic, hydrophobic (nonpolar) regions, hydrophilic (polar) regions. Want more fluids increase unsaturated fats: increases the fluidity of the membrane. What kind of molecules would pass through a phospholipid bilayer: small and nonpolar. Direction of movement: expect down the concentration gradient, what about against the concentration gradient, sodium5-15mm in the cell ; 145mm outside. When concentrations on both sides of a barrier are equal: molecules keep moving, no net charge solute. Semi-permeable barrier: only some type of molecules pass through. Diffusion: movement of molecules down concentration gradient from high to low, physical property of matter, individual molecules move randomly, but the net effect is non- random. Movement of water across membranes: from high to low water potential.
