Membrane Transport 12-15 points (12-15%) Understand what types of molecules/ ion
ID: 3510066 • Letter: M
Question
Membrane Transport 12-15 points (12-15%) Understand what types of molecules/ ions can move through the cell membrane by: A) Simple diffusion, B) facilitated diffusion channels and how they can be gated, C) facilitated diffusion carriers and why they are for larger molecules, how they can be saturated), D) primary active transport and the direct use of ATP and E) secondary active transport- Know how each of the above works, what energy drives them (diffusion gradient, ATP or other) and a specific example of each.Explanation / Answer
A. Simple diffusion
it is the process by which materials move from an area of high concentration to the area of low concentration. it is a type of passive transport and does not require energy. it is run by the concentration gradient or the difference in the degree of saturation.
eg. small , non polar molecules like oxygen and carbon dioxide move across the cell membrane by simple diffusion
B. facilitated transport via channels
this is also a passive tranport from high concentration to low concentration via a channels. these are water filled channels which will overcome the problem that some larger molecules face while crossing the lipid bi layer of the membrane. these channels can be gated or opened and closed by external ligands like neurotransmiters,mechanically by sound, voltage gated etc . this is also a type of passive transport and do not require energy
eg . binding of acetylcholine at the synapsed will open the sodium channels and cause nerve excitation
C.facilitated diffusion by carriers
This is also transport across a membrane through protein carrier. these transmembrane proteins have pores though which the materials cross according to the concentration gradient.
eg . transport of Oxygen from blood to RBC
D. Active transport is the transport of materials against the concentration gradient (ie from low concentration to high concentration ) by the expenditure of energy. this is done by using spcialised pumps.
eg . Sodium Potassium ATP ase pump actively pumps potassium in to and sodium out of the pump maintaining the resting membrane potential
E. Secondary active transport . it is the tranport of materials accross a membrane against the concentration gradient by using energy other than ATP like the electromechanical gradient caused by the movement of other ions in opposite direction.
eg.Sodium Hydrogen antiport in Kidney