Introduction

We have reached our discussion on the smallest unit of life, the cell. For many students, this module is one of their favorites. In Module 1, you worked to gain a general understanding of the chemistry of life, and then put those concepts together to think about how and why certain atoms interact to form important organic molecules of the cell. You took a closer look at these individual molecules, their structure, and their general functions and in this module you will put all of these concepts together to gain an understanding of how they work together to promote the life of the cell, the basic unit of life.

In addition to defining the function of the individual structures within the cell, be aware that there is communication among the structures within the cell. An example is the act of producing a lysosome. The digestive enzymes found in the final product (lysosomes) are produced in the rough endoplasmic reticulum. A vesicle buds off of the rough endoplasmic reticulum and carries the digestive enzymes to the golgi apparatus, where the vesicle will dock and fuse. The membrane of the vesicle becomes a part of the golgi apparatus and “dumps” the digestive enzymes into the golgi. Once the final vesicle buds off of the golgi apparatus carrying the digestive enzymes within, this is called the lysosome, and is an example of two compartments/ organelles acting together within the cell.

In this module, think about the “cell theory”, compare eukaryotes and prokaryotes, and then take a close look at the structures within the cell and the functions they provide to the cell on the whole. When you are reviewing the structures within the cell, also keep in mind the size of the cell (small; how small?) and the idea that the structures within the cell have their individual functions, but also interact with each other to promote the overall functioning of the cell.

Another important concept to consider in this module is that as cells specialize, they develop more or less of the organelles listed above. For example, red blood cells (RBCs) in the body will actually squeeze the nucleus out of the cell during development. Why? The nucleus is often thought of as the “brain of the cell”, since this is where your genetic information, DNA, is stored. Consider the theme “structure equals function” from Module 2 and apply it to the function of the red blood cell. This particular cell’s main function is carrying oxygen to nourish the cells of the body. To this end, RBCs are packed full of hemoglobin and squeezing the nucleus out of the cell can be seen as a way to pack in more hemoglobin molecules and allow for more oxygen to be carried. You will explore cell specialization in the discussion board for this module ¹ .