recap

5.1 recap

The cell theory is a unifying principle of biology. Cell size is limited in order to maintain a high surface area-to-volume ratio. Both prokaryotic and eukaryotic cells are enclosed within a cell membrane, but prokaryotic cells lack the membrane-enclosed organelles that are found in eukaryotic cells.

learning outcomes

You should be able to:

  • List the three tenets of the original cell theory.

  • Explain the importance of membranes in cell function.

Question 1

How does cell biology embody all the principles of life?

Life is continuous: the cell theory explains that this comes from cell continuity. Life is complex chemically: the cell theory states that this chemistry occurs within cells. Life evolves and changes over time: the cell theory states that evolution occurs in cells as they change genetically and pass on new characteristics to the next generation of cells.

Question 2

What is the importance of the cell membrane and the membranes that surround organelles?

The membranes that enclose cells and organelles create compartments. The cell membrane allows the chemical reactions of life to occur away from the surrounding environment; in particular, the cell membrane permits the internal environment to have a distinct composition and concentration. Organelles’ membranes permit specialized functions and keep harmful substances away from the rest of the cell (cytoplasm).

86

As we mentioned in this section, there are two structural themes in cell architecture: prokaryotic and eukaryotic. We will now turn to the organization of prokaryotic cells.