Chapter 12, Problem 12.1CC

How do differences in the structure and arrangement of rough versus smooth ER reflect their different functions?

Summary Introduction

To explain: The way in which difference in the structure and arrangement reflects the functions of the rough endoplasmic reticulum (ER) and the smooth endoplasmic reticulum (ER).

Introduction: Cell is the basic “fundamental unit” of life. Cells can either be unicellular or multicellular. There are various types of cell on the basis of shape and size such as red blood cells (circular), muscle cells (spindle-shaped) and so on. One of the cell organelles is found in the cell known as endoplasmic reticulum (ER). It is a network of tubules membrane inside the cytoplasm of the cell.

Explanation of Solution

The major difference between the rough endoplasmic reticulum and the smooth endoplasmic reticulum is the presence of ribosomes.

• Rough ER:

  The presence of ribosomes on the ER provides it its rough structure. The presence of ribosomes on the structure of the rough ER supports in the process of protein synthesis (translation). The protein synthesis takes place by the presence of mRNA which carries the signals from the nucleus to the cytoplasm and guides the process of translation.

• Smooth ER:

  The absence of the ribosomes on the structure of the ER represents the structure of the smooth ER. However, due to the absence of the ribosomes in the structure of the smooth ER does not take part in the synthesis of the proteins. The function performed by the smooth ER is the synthesis of lipids which supports in the structure of the plasma membrane.

Thus, the arrangement of the ribosomes on the structure of ER functionally differentiates both the ER.