The Cell Surface Membrane Flashcards
The phospholipid bilayer is an important component of cell membranes, how is this bilayer arranged?
Hydrophobic tails point inwards and hydrophilic heads point outwards
The cell surface (plasma) membrane forms a boundary between the environment and the cell cytoplasm, why is this needed?
Allows different conditions to be established and keeps them separated (homeostasis)
Partially permeable - controls exchange cells between cells and environment
What are the functions of phospholipids in membranes?
Allow lipid soluble substances to enter/leave cell
Prevent water soluble substances entering/leaving cell
Make the membrane flexible
What are the two ways in which the proteins in membranes are embedded in the phospholipid bilayer?
Extrinsic - either on surface or partly embedded. Give mechanical support or act as cell receptors.
Intrinsic - span bilayer from one side to the other. Act as carriers or enzymes.
What is the importance of cholesterol in membranes?
Controls membrane fluidity; more cholesterol - less fluid - less permeable
Keeps membranes stable at normal body temperature - without it cells would burst open
What is the fluid mosaic model and why is it called this?
The way in which the various molecules are combined into the structure of the cell surface membrane is known as the fluid mosaic model
Fluid - phospholipids can move - gives membrane a flexible shape that is constantly changing - fluid like
Mosaic - proteins in membrane vary in size, shape and pattern in the same way as the tiles of a mosaic
