Chapter 13 membrane channels and pumps questions

Na+/K+ pumps: extracellular side of the pump

-binding of cardiotonic steroids -binding of K+

E1-P

-high affinity for calcium -ion binding sites open to the cytosol

E1:

-high affinity for calcium -is phosphorylated by ATP on calcium binding -ion binding sites open to the cytosol

Na+/K+ pumps: intracellular side

-hydrolysis of ATP and phosphorylation -binding of Na+

E2-P

-low affinity for calcium -ion binding sites open to the luminal side of the membrane

E2

-low affinity for calcium -ion binding sites open to the luminal side of the membrane -is dephosphorylated upon the release of calcium

which of the following is an example of simple diffusion? a. passage of steroid hormones through a membrane b. movement of sodium ions across a membrane c. transport of glucose across a membrane d. transport of lactose across a membrane

A simple diffusion involves the passage of lipophilic molecules across a membrane according to their concentrations gradient

what is true about membrane channels, carriers, and pumps? a. all are integral,transmembrane proteins b. all can be ligand or voltage gated c. all contain multiple subunits or domains d. all carry out active transport of ions and polar molecules e. all allow bidirectional flux of the transported molecule

A, C

which of the following describes properties that are common to the calcium ATPase of the sarcoplasmic reticulum and the sodium/potassium pump? a. both are abundant membrane proteins in the sarcoplasmic reticulum b. both have homologous N-terminal subunits containing ABC numerous transmembrane helices c. both contain an aspartate residue that is phosphorylated by ATP d. both translocate the same number of ions per transport cycle e. both probably have four major conformational states

B, C,E

which of the following statements about proteins containing ABC domains is NOT correct? a. they are members of the p-loop NTPase superfamily b. they usually consist of two membrane spanning domains and two ATP binding domains c. the membrane spanning domains and ATP binding domains are always on separate polypeptide chains d. the ABC domains undergo conformational changes upon ATP binding and hydrolysis

C while prokaryotic ABC proteins are often multisubunit proteins, eukaryotic ABC proteins usually contain both membrane spanning and ATP binding domains on the same polypeptide

which of the following are used as forms of energy that can drive active transport? a. light absorption b. ATP hydrolysis c. ion gradient d. a and b e. all of the above

E

explain how the MDR protein functions in the phenomenon of multidrug resistance

the multidrug resistance (MDR) protein is 170 kD P-glycoprotein that is expressed in cells displaying multidrug resistance. it acts as an ATP dependent pump that extrudes a wide range of small molecules from cells that express it. when cells expressing the MDR protein are exposed to a drug, they are pumped out of the cell before the drug can exert its effects

explain why an electric current is generated during the transport of sodium and potassium by the sodium-potassium pump

three sodium ions are transported out for every two potassium ions that are transported in, so there is a net efflux of oe positively charged ion. the net movement of ions sets up an electric current