CEL - Types of Cells [LESSON]

Types of Cells

Classification

Life is categorized into three domains and six kingdoms. They are listed in the table below. Note that Archaea and Eukarya are the two most closely related domains. This means that you are more closely related to a mushroom than an archaean is to a bacteria!

 Kingdoms Classified into Type of Cell and Domain Table

Prokaryotic vs eukaryotic cells

The image above depicts an average prokaryotic cell. There are two types of cells: prokaryotic and eukaryotic. Prokaryotic cells contain neither a nucleus nor membrane-bound organelles. However, prokaryotic cells have DNA and several specialized structures. You can think of a prokaryotic cell as a small business where everything is achieved by one or two workers all in one small area. As the business grows, this model no longer works – we have to split up the jobs of the cell into different departments. 

 

Eukaryotic cells are larger and much more complex than prokaryotic cells. In fact, their size presents a challenge. With increasing size, the ratio of surface area to volume becomes smaller as we studied in Lesson 1. Such a decrease in surface-to-volume ratio results in challenges to obtaining nutrients and exporting wastes relative to the volume of the cell. Eukaryotic cells have small compartments or organelles that both increase the membrane ratio and bring all required parts of a certain cellular job to the same location. 

Watch the following video to learn more about Prokaryotic and Eukaryotic Cells.

What are the differences between prokaryotic and eukaryotic cells? Click the learning object below to see the differences.

Endosymbiotic theory

First, remember that a theory is the MOST supported category in the realm of science.  A theory explains natural phenomena according to a vast array of evidence.  For example, the theory of gravity tells us that objects are attracted to each other according to their mass or energy.  Cell theory tells us that living things are made of cells, that they are the basic structural unit of all living things, and that all cells come from pre-existing cells.  Where then did the first cell come from?  We will explore that topic in the second semester.  For now, we will discuss the endosymbiotic theory which explains how the first eukaryotic cells arose from living inside of other cells. 

Watch the Endosymbiosis Theory video below to learn about how the first eukaryotic cells arose.

Now, click below to learn about the evidence for the endosymbiotic theory.

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