1. Fully explain the role of ATP in the sodium potassium pump.
Sodium potassium pump is a primary active type of cell transport where in it pumps ions against the concentration gradient. In the human cell, sodium and potassium are essential ions in maintaining normal fluid volume moreover it is an important ions that maintains the function of excitable cells such as nerve and muscles cells in transmitting impulses or contracting the muscles. The mechanism is that the sodium potassium pump pumps potassium ions from outside the cells to the inside of the cell while at the same time it pumps sodium ions from inside to outside the cell. Since this type of transport is a transport that pumps ions against the concentration gradient knowing the potassium is more on the inside of the cell while sodium is more on the outside of the cell, transporting these ions against their concentration gradient necessitates an active energy and this type of energy is achieved through the phosphorylation of ATP known as adenosine triphosphate.
ATP basically is being phosphorylated as soon as the ion attaches to the carrier protein on the plasma membrane, the bonds on the phosphate group are broken thereby releasing energy. The energy which was released is used by the carrier protein channel in changing its shape thereby transporting sodium ions from inside to the outside of the cell and potassium ions from outside to the inside of the cell (book p. 73 -74).
2. Would a 2% solution of NaCl cause a red blood cell to crenate (shrink) or swell? Explain your answer.
Osmosis is a type of passive transport where water molecules pass through a selectively permeable membrane from an area of greater concentration to an area of lesser concentration. This is basically achieved because of the random movement of the membrane lipid thereby opening small gaps between the wiggling tails of the lipid bilayer and the transmembrane proteins which are water specific called the aquaporins which allow water molecules to pass through the plasma membrane. Aquaporins are particularly abundant in red blood cells and kidney/tubule cells. The water molecule movement along its concentration gradient depends on the concentration of the solute particles or osmolality on either side of the membrane which decreases the concentration of the water.
To answer the question, a 2% NaCl will cause red blood cell to shrink because the water will move from the inside of RBC to the outside of RBC.