movement across cell membrane

Question 1

state the 4 ways in which small molecules can travel across the cell membrane

Answer 1

passive diffusion, facilitated diffusion, active transport and endocytosis

Question 2

describe the process of passive diffusion

Answer 2

this is diffusion directly through the lipid bilayer or through aqueous pores(aquaporin) that go across membrane
many lipid soluble drugs cross the membrane this way

Question 3

describe the process of facilitated diffusion

Answer 3

this is diffusion via special carrier proteins that bind the drug on one side of the membrane, undergo conformation change, and release the drug on the other side
doesn’t require energy but requires conc. gradient

Question 4

describe the process of active transport of a drug across the membrane

Answer 4

requires energy, via specialised carrier proteins and can go against the conc. gradient

Question 5

describe the process of endocytosis

Answer 5

this is when the drug on the outside of the membrane is encased by a part of the membrane, after invagination of part of the membrane, and released on inside
used to transport large drugs across membrane