Lectures 7 & 8: Cell Membrane Function Flashcards
What are phospholipids?
A lipid that has a hydrophilic head and contains a phosphate group and two hydrophobic tails. They are abundant in the cell membrane and are amphipathic molecules.
What is the fluid mosaic model?
The membrane has fluid within a mosaic of proteins embedded into it.
What are the six major functions of membrane proteins?
Transport, Enzymatic activity, Signal transduction, cell to cell recognition, intracellular joining, attachment to cytoskeleton and extracellular matrix (ECM).
What are lipid bilayers not permeable to and why?
Ions (potassium, sodium, calcium, chlorine and HCO3), small hydrophilic molecules like glucose and fructose (too polar to get across), macromolecules like proteins and RNA (too big).
What is osmosis and when does it occur?
Osmosis occurs when a solute cannot cross the cell membrane, so water moves instead. Water moves by passive diffusion (no ATP required), but mainly through water channels (aquaporins).
What is osmotica?
These are solutes that are not osmotically active, such as ions, sugars and proteins.
How do you calculate osmolarity (Osm/L)?
Molar concentration x number of molecules or ions in a solution
What is tonicity?
The ability of a solution to cause a cell to gain or lose water
Isotonic solution?
A solute concentration is the same as that inside the cell; no net water movement across the plasma membrane.
Hypertonic solution?
Solute concentration is the same as that inside the cell; no net water movement across the plasma membrane.
Hypotonic solution?
Solute concentration is less than that inside the cell; the cell gains water.
What is the effect of tonicity on human red blood cells?
If the osmolarity is 50 Osm/L then it is hypotonic and the cells are lysed, then the cells volume increases when the solutions osmolarity is 300 Osm/L, it is the normal cell volume and is an isotonic solution. When the osmolarity increases to 500 Osm/L then the cell decreases and the solution becomes hypertonic.
