The Cell: Revision
Cells are the basis of life, as we know it. All cells have a membrane surrounding cytoplasm in which floats DNA, and ribosomes. The basic functions of all cells are similar.
However, within this general description we find many different types of cell. The most important divide is between Prokaryotic (Pro – before, karyote – nucleus) and Eukaryotic cells.
Prokaryotic cells are comparatively simple, and small. The DNA is found in circles or loops and it floats in cytoplasm. Ribosomes (70S in size) are also found in the cytoplasm. While some cells have internal membranes, most have only a porous outer membrane with a semi permeable inner membrane. Prokaryotic cells are commonly referred to as bacteria (see Ch 33 in your text), though the group includes the superfamilies of Archaea and Eubacteria, which have huge biochemical differences between them.
Eukaryotic cells are structurally complex and they are generally larger than bacterial cells. Eukaryote cells have membrane bound organelles. Their DNA is organized into linear threads called chromosomes which are located within a membrane, and the entire unit is called a nucleus. Organelles that might be found in a cell include ribosomes (80S), mitochondria, chloroplasts and golgi. The organelles are linked by membranes. Their position and the activity of organelles within the cell is regulated by the cytoskeleton. The cytoskeleton has two main components, microfibrils made of actin and microtubules made of tubulin (see Chapter 3 of your text). Animals, Plants, Fungi and Protista are found within the Eukaryota.
To test your knowledge complete the following drag and drop exercise.
Drag & Drop Exercise
