Chapter 7, Problem 16A

Summary Introduction

To explain:

The plasma membrane maintains homeostasis within a cell.

Introduction:

The cell maintains a steady state of internal equilibrium by maintaining balance in its physical and chemical components. The internal environment of the cell is separated from the external surroundings by the plasma membrane.

Explanation of Solution

The plasma membrane is the boundary that delimits the internal cellular environment. It is made up of a phospholipids bilayer and surrounds the cell. It is selectively permeable and allows passage of only some specific materials through it. The selective permeable nature of the plasma membrane allows cells to maintain higher concentration of sodium ions and potassium ions on the outer and inner side of the membrane respectively.

The plasma membrane also maintains and regulates the water balance to an optimum level inside the cell by slowing the movement of water into or out of the cell. In addition, the cell membrane helps to maintain membrane fluidity. The plasma membrane is a phospholipid bilayer with an electrically charged head region and an oily tail. In case of decrease in membrane mobility, the oily regions can crystallize into a solid which can adversely affect the cells ability to regulate ions and water.

Conclusion

The plasma membrane maintains the internal balance of several factors. It regulates the passage of water and ions, maintaining their optimum concentration level at all time. The fluidity of the plasma membrane is also maintained so that the cell can adjust to changing environmental conditions.