Transport Across Cell Membranes Flashcards
Why is the cell membrane called the fluid-mosaic model?
It is fluid because the individual phospholipids can move, giving the membrane flexibility. It is a mosaic because the proteins vary in size and shape, similar to tiles or stones in a mosaic.
What elements make up the cell surface membrane?
Phospholipid bilayer, proteins (carrier and channels),cholesterol, glycolipids and glycoproteins.
What is the function of cholesterol in the cell membrane?
Reduce movement of the phospholipids and prevent leakages of water and ions in the cell.
Name the 2 types of transport proteins found in the cell membrane?
Protein channels and carrier proteins
Transport proteins are specific, what does this mean?
They are selective, and only work in the presence of specific ions.
What features would you expect to see in cell membranes where rapid diffusion is needed?
Define facilitated diffusion?
Movement of charged or larger molecules across the membrane facilitated by proteins within the membrane.
Define simple diffusion?
The net movement of molecules or ions from an area of high to low concentration until they are evenly distributed.
When does diffusion stop?
Until they are distributed evenly at equilibrium.
What characteristics do molecules have t have in order to cross a membrane through simple diffusion?
Small
Non polar
What factors will affect the rate of diffusion of oxygen into a cell?
Temperature, concentration gradient, thickness of membrane, surface area
Define osmosis?
The net movement of water from an area of high water potential to lower water potential through a selectively permeable membrane.
What are the units of water potential?
KPa
Describe and explain what would happen to an animal cell places in pure water?
Define water potential?
Water potential is pressure exerted by water molecules on the membrane. If a solution has a high water potential, it has a high water concentration (not much solute dissolved in it).
