University:
California State University, Northridge
Course:
BIOL 100 | Introductory Biology
Academic year:

2021
Views:

89

Pages:

2
Author:

B. Coleman

SUMMARY CELL BIOLOGY 1. The cell membrane structure is mainly composed of a phospholipid bilayer with amphipathic properties, namely the lipid head structure which has hydrophilic properties andthe tail structure which has hydrophobic properties. 2. Apart from the phospholipid bilayer, the cell membrane also contains proteins that are found between the phospholipid bilayer or bind to one of the lipid layers on the inside (cytosol) or on the outside (extracellular). The proteins that make up membranes can be classified into three categories, namely 1) integral proteins, 2) proteins bound to fat, and 3) peripheral. 3. The existence of a cell membrane provides semi-permeability for the cell so that certain molecules and gases can freely pass through the membrane and other molecules or gases require a special mechanism to pass through the cell membrane. 4. Transport of substances in or out of cells, including: diffusion, facilitated diffusion, osmosis, endocytosis and exocytosis. 5. Active transport is active diffusion where there is a mechanism for the entry of certain substances or ions into cells that require the help of proteins and require energy in the form of ATP. The presence of proteins and the types of molecules that enter produce uniport, symport and antiport conditions. 6. Osmosis, which is a mechanism for the entry of water into cells, causes different situations in cells, namely isotonic, hypotonic and hypertonic. 7. Large molecules require a special mechanism to enter the cell, namely through the endocytosis mechanism and through the endolytic pathway, molecules that have been digested by lysosomes can be released again through the exocytosis mechanism.