Endoplasmic Reticulum

Cytoplasm and Its Organelles

The cytoplasm is filled with both minute and large dispersed particles and organelles. There are five important organelles: the endoplasmic  reticulum, Golgi apparatus, mitochondria, lysosomes  and  peroxisomes.

Endoplasmic Reticulum

             

It's  a network

of tubular and flat vesicular structures in the cytoplasm, their walls are constructed of lipid  bilayer  membranes that contain large amounts of proteins.  

The  vast surface area of this reticulum and the multiple enzyme systems attached to its membranes provide machinery  for a major share of the metabolic functions of the cell.

Ribosomes and the Granular Endoplasmic Reticulum.  

            Attached to the outer surfaces of many parts of the endoplasmic reticulum are large numbers of minute granular particles called ribosomes. Where these are  present,  the  reticulum  is    called  the    granular endoplasmic

Reticulum, they function to  synthesize  new protein molecules in the cell.

Agranular Endoplasmic Reticulum.

Part of the endoplasmic  reticulum has no attached   ribosomes. This part  is called the a granular, or smooth, endoplasmic reticulum. The  a granular reticulum functions is  synthesis of lipid substances