Chapter 7, Problem 13STP

Summary Introduction

To explain:

The cell membranes, if were not selectively permeable.

Introduction:

The cell membrane surrounds the cell and helps it to protect it from any environmental fluctuations. The plasma membrane of the cells is selectively permeable which an essential property is as it only allows certain molecules to enter or exit the cell.

Explanation of Solution

The presence of a selectively permeable membrane helps the cell to regulate and exercise control over timings and rate of movement of the ions and molecules. It is made up of a phospholipid bilayer, along with other carbohydrates, proteins and lipids.

In case, the cell membrane is completely permeable, the cell will have no control over the influx and out flux of the molecules and almost all molecules will gain access to the inside of the cell. As there is no regulation, several toxins, viruses, pathogen harmful substances will able to damage the cell and ultimately, kill it.

In case, the membrane is fully impermeable, the cell cannot get rid of its toxin byproducts and these will accumulate inside the cell. As a result, biological processes will get disrupted leading to cell death.

Conclusion

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 a balanced atmosphere.