Exam 10: Membrane Transport

Drug resistance is frequently traced to (I)the MDR transporter. (II)overexpression of P-glycoprotein. (III)increased number of specific ABC transporters. (IV)the evolution of selectivity filters.

Which features allow the KcsA channel to selectively transport K⁺? (I)The entrance of the channel contains hydrophobic residues which forces the removal of waters of hydration. (II)It is attracted to the entrance of the channel via electrostatic interactions. (III)The "selectivity filter" involves a narrowing of the channel,allowing only dehydrated K⁺ access. (IV)As K⁺ is transported through the channel it interacts with −C=O groups from the protein.

Matching -KcsA is an example of a(n)_________.

D-glucose is added to cells and the rate of glucose transport is plotted against D-glucose concentration.In the presence of the D-galactose derivative 6-O-benzyl-D-galactose,the curve is shifted to the right,indicating that D-glucose and the D-galactose derivative both compete for a place in the binding site.Which of the following is true?

Matching -The GLUT1 transporter functions via _____ transport.

Of the transport proteins discussed in the chapter,in general,which of the following do they have in common?

The rapid transport of K⁺ ions by the KcsA ion channel moves up to ____ ions per ______.

Based on the figure below,this system represents _______.

Matching -The Ca²⁺-ATPase requires ATP directly and is therefore an example of ______ transport.

Matching -______ are transporters that bind the substance to be transported on one side of the membrane then diffuse through the membrane and release the substance on the other side.

Which statement about aquaporins is false?

Matching -A transporter that moves two substances simultaneously in the same direction is an example of a(n)__________.

Gap junctions

The Kv channel is transiently closed by ___________.

In the intestinal epithelium,glucose enters the cell in symport with ______,which is subsequently ejected by ________.

A patient has low levels of potassium.Which of the following could be affected? (I)levels of calcium available for cardiac muscle (II)amount of glucose transported through the intestinal lumen (III)amount of lactose metabolized (IV)chloride ion transport may slow

Based on the diagram below,which of the following statements is TRUE?

Which of the following is evidence for aquaporins?

Which of the following is (are)characteristic of the (Na⁺-K⁺)-ATPase? (I)It binds Na⁺ and K⁺ simultaneously prior to binding ATP (II)It is covalently modified by phosphorylation at an Asp residue when Na⁺ is present. (III)Transport of Na⁺ and K⁺ occur in a 1:1 ratio,thus maintaining a balanced gradient until opening of the gated portion of the channel. (IV) It is essential for excitation of nerve cells.

Which of the following correctly rank the steps in erythrocyte glucose transport by GLUT1? (I)Glucose binding results in a conformational change,opening the binding site on the opposite side of the membrane (II)Glucose binds to the transporter on one side of the membrane (III)The transporter reverts to initial conformation (IV)The glucose disassociates