a couple of question about cell transport...?

Question

my teacher just shifted through the topic, and i went online to do some reasearch to try to understand-and i found these statements-what on earth do they mean?

1)Na+/k+ AtPase of animal cells
Advantage of antiport system: charge compensation
3:2 ratio of Na+/K+ transport compensates for ion leakage differential.

2)Aquaporin
H20 molecules become aligned by interaction with ASN molecules at constriction sites

pls don't give me wikipedia links-i know the website.

Answer 1

Animal cells use a sodium pump (the Na/K ATPase) to make a voltage gradient across the plasma membrane. It pumps three sodium ions out for every two K ions that go in. Since 3 positive charges are going out, and two are going in, there is a net movement of positive charges out of the cells (and hence a voltage across the membrane: inside negative and outside positive). Na levels are greater outside the cells and Na "wants" to go back in down its chemical gradient. The external Na+ also "wants" to go back into the negatively charged cell interior. The movement of Na+ ions back ino the cell is an example of charged particle moving though space (i.e., electricity). Electricity can be used to do work (like moving an anion against its concentration gradient). Antiporters couple the energetically extremely favorable movement of sodium back into the cell with energetically slightly unfavorable movement of anions into the cell. Since a positive and negative charge are entering the cell, it is a charge neutral process.

Aquaporins are membrane protein channels that transport water across the hydrophobic membrane. Asn is an abbreviation for asparagine, one of the 20 amino acids. Presumably, asparagine residues in some constricted area within the aquaporin pore help regulate this process.