The plasma membrane surrounds the cell to create a barrier between the cytosol and the extracellular matrix. Plasma membranes also enclose lumens of some cellular organelles.
2.Endoplasmic reticulum
The endoplasmic reticulum (ER) is a large network of membranes responsible for the production of proteins, metabolism and transportation of lipids, and detoxification of poisons. There are two types of endoplasmic reticulum with separate functions: smooth endoplasmic reticulum and rough endoplasmic reticulum. The presence or absence of ribosomes in the ER’s plasma membrane determines whether it is classified as smooth or rough ER.
3.Golgi apparatus
The Golgi apparatus appears as a series of flattened, membranous sacs, or cisternae, that resemble a stack of pancakes just off the rough endoplasmic reticulum. It receives vesicles containing proteins recently produced by the rER. The Golgi apparatus can be compared to a warehouse or post office for newly formed proteins. Here the proteins are further modified, packaged, and sent off to their final destinations in the cell or body.
The major function of DNA is to encode the sequence of amino acid residues in proteins, using the genetic code. To read the genetic code, cells make a copy of a stretch of DNA in the nucleic acid RNA.
