Lesson 1

In this lesson, we will cover:

• Cells as building blocks
• Cell composition
• Prokaryotes and eukaryotes

The cell is the basic unit of life. The cell theory, set forth in the 1850's, says that:

• Cells are the fundamental units of life, because a cell is the simplest unit capable of independent existence.
• All living things are made of cells.

Cells are 90% water. The rest of the present molecules are:

• 50% protein
• 15% carbohydrate
• 15% nucleic acid
• 10% lipid
• 10% others

By elements, a cells composition is:

• 60% Hydrogen
• 25% Oxygen
• 10% Carbon
• 5% Nitrogen

Eukaryotes could be said to have a more complex form than that of prokaryotes. Eukaryotes have a nucleus and membraned-bound organelles, while prokaryotes do not. The DNA of prokaryotes floats around the cell, while the DNA of eukaryotes is trapped in the nucleus. On the average, eukaryote cells are ten times larger than prokaryote cells. The DNA of eukaryotes is much more complex than that of prokaryotes. Prokaryotes have a cell wall made up of peptidoglycan, a large polymer consisting of amino acids and sugar. Many kinds of eukaryotic cells also have cell walls, but none are made of peptidoglycan. Prokaryotes and eukaryotes have many similarities, also.

• They both have DNA as their genetic makeup
• They are both contained by a membrane
• They both have ribosomes
• They have a basic metabolism
• They both have many different forms

That's it! You have made it through lesson 1, an introduction to cells. If you want to proceed to the next lesson, first take the lesson 1 quiz.