Biology Chapter 4: Inside the Cell
The cell is the smallest structural and functional unit of an organism, consisting of cytoplasm and a nucleus surrounded in a membrane. Cells are microscopic in size. Cells must remain small in order to have an adequate amount of surface area per cell volume.
All cells have a plasma membrane, cytoplasm, and genetic material. Prokaryotic cells do not have a membrane-bound nucleus. Eukaryotic cells have a membrane-bounded nucleus and also do various membranous organelles. Bacteria are representative of the prokaryotes. They have a cell wall and capsule, in addition to a plasma membrane. Their DNA is in the nucleoid. They have many ribosomes and three possible appendages.
The plasma membrane of both prokaryotes and eukaryotes is a phospholipid bilayer. The phospholipid bilayer regulates the passage of molecules and ions into and out of the cell. The fluid-mosaic model of membrane structure shows that the embedded proteins form a varying pattern. The types of embedded proteins include channel, transport, cell recognition, receptor, enzymatic proteins.