By the end of this lesson and the next few, you should be able to:
- Describe the structure of eukaryotic cells
- Compare animal cells with plant cells
- State the role of the plasma membrane
- Summarize the functions of the major cell organelles
Introducing Eukaryotic Cells
Have you ever heard the phrase “form follows function?” Basically, it’s a philosophy which many industries practice. In architecture, this means that buildings should be constructed to support the activities that will be carried out inside them. For example, a skyscraper should be built with several elevator banks; a hospital should be built so that its emergency room is easily accessible.
Our natural world also utilizes the principle of form following function, especially in cell biology. Actually, this will become clear as we explore eukaryotic cells (see image below). Unlike prokaryotic cells, eukaryotic cells have:
- a membrane-bound nucleus;
- numerous membrane-bound organelles such as the endoplasmic reticulum, Golgi apparatus, chloroplasts, mitochondria, and others; and
- several, rod-shaped chromosomes.
These figures show the major organelles and other cell components of (a) a typical animal cell and (b) a typical eukaryotic plant cell. The plant cell has a cell wall, chloroplasts, plastids, and a central vacuole—structures not found in animal cells. In fact, plant cells do not have lysosomes or centrosomes. Image Attribution: OpenStax Biology
Because a membrane surrounds a eukaryotic cell’s nucleus, we often say it has a “true nucleus.” The word “organelle” means “little organ,” and, as already mentioned, organelles have specialized cellular functions, just as the organs of your body have specialized functions.
At this point, it should be clear to you that eukaryotic cells have a more complex structure than prokaryotic cells. Organelles allow for the categorization of different functions in different areas of the cell. Before turning to organelles, let’s first examine two important components of the cell: the plasma membrane and the cytoplasm. We’ll do this in the next lesson.