Eukaryotic cells have organelles which may
(a) not be bound by a membrane
(b) bound by a single membrane
(c) bound by a double membrane

Solution: (a) Cell organelles with no membrane In eukaryotic cell, ribosomes occur freely in the cytoplasmic matrix and are attached to the outer cytoplasmic surface of the rough matrix of mitochondria and stroma of plastids called as mitoribosomes and plastidoribosomes, respectively.
(b) Cell organelles with single membrane A lysosome is a tiny sac bounded by a single unit membrane of lipoprotein. The lysosomes occurs in all animal cells and protozoans. Prokaryotic cell lack lysosomes.
Number of lysosomes varies with the cell type. Lysosome contain a dense, finely granular fluid consisting of glycoproteinaceous hydrolytic (digestive) enzymes called acid hydrolases. Cell organelles like sphaerosomes and microbodies also possess single membranes.
(c) Cell organelles with double membrane Mitochondria are double membrane bound structures with the outer membrane and inner membrane dividing its lumen distinctly into two aqueous compartments.
The inner compartment is called the matrix whereas the outer membrane forms the continuous limiting boundary of the organelle. Chloroplast and nucleus are also double membrane bound organelles.