You are doing an experiment with liposomes (spherical vesicles with phospholid b
ID: 164353 • Letter: Y
Question
You are doing an experiment with liposomes (spherical vesicles with phospholid bilayers) containing only one protein in their membranes: Na^+ -K^+ pumps. Inside the membrane of those vesicles, the Na^+ -K^+ pumps are in the same orientation as they are usually found in the cell. That is, all of the Na^+/K^+ pumps are oriented so that: they are pumping Na^+ out of the cell and K^+ in to the cell AND the portion of the Na^+ -K^+ pumps that normally faces the cytoplasm of a cell is facing the inside of the vesicle For each of the conditions below, predict what would happen to the transport of Na^+ and K^+ and explain your answer. There is no ATP either inside or outside the cell There is ATP inside the cell, but no ATP outside of the cell. There is ATP, and Na^+, both inside and out of the cell, and there is no K^+.Explanation / Answer
A. The pump requires an ATP every time it works, ATP must be constantly supplied to the cell. ATP is created during the processes called "cellular respiration" which occur inside the cell. Part of cellular respiration happens in the cytoplasm and part happens in the mitochondrion. Since these organelles are part of the nerve cell, as the ATP is made, it floats up to the pump and provides its energy. More ATP is made and the pump continues to do its job. If something interferes with the production of ATP, the pump will stop working and the nerve cell will also stop working. This can cause serious loss of nerve function and even death. Since cellular respiration requires oxygen, if you were to stop breathing, ATP could not be produced and you would die. Of course ATP is needed by many processes in the body so it is not only the Na/K pump that would stop.
b. The Na/K pump illustrates active transport since it moves Na+ and K+ against their concentration gradients. That is because there is already a high concentration of Na+ outside the cell and a high concentration of K+ inside the cell. In order to move the ions against their gradients, energy is required. This energy is supplied by ATP (adenosine triphosphate). An ATP molecule floating inside the cell, binds to the pump transferring some energy to it. As the energy is used, the ATP falls off and having lost its energy it is converted into ADP (adenosine diphosphate). The Na/K pump will work effieciently.
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