Ribosomes of eukaryotic cell

i. Ribosomes are protein factories of cell and were first observed as dense particles in electron micrograph of a cell by scientist Palade in 1953.

ii. Ribosomes lack membranous covering around them and are made up of Ribosomal RNA and proteins.

iii. In a eukaryotic cell, ribosomes are present in mitochondria, plastids (in plant cells) and in cytosol.

IV. Ribosomes are either found attached to outer surface of Rough Endoplasmic Reticulum and nuclear membrane or freely suspended in cytoplasm.

V. Both are of 80S type. Each ribosome is made up of two subunits- a large (60S) and a small (40S) subunit. 

Vi.  Bound ribosomes generally produce proteins that are transported outside the cell after processing in ER and Golgi body. e.g. Bound ribosomes of acinar cells of pancreas produce pancreatic digestive enzymes.

Vii.  Free ribosomes come together and form chains called polyribosomes for protein synthesis.

Viii.  Free ribosomes generally produce enzymatic proteins that are used up in cytoplasm, like enzymes required for breakdown of sugar. 

ix. Both types of ribosomes (bound and free) can interchange position and function.

X. Number of ribosomes is high in cells actively engaged in protein synthesis.