Q.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
Group the various sub-cellular organelles into these three categories.

Eukaryotic organelles can be sorted by whether, and how, they are bound by a membrane.

• Not bound by any membrane: ribosomes (a compact particle of RNA and protein with no membrane of its own) and structures like the centriole and the cytoskeleton's filaments.
• Bound by a single membrane: the endoplasmic reticulum, the Golgi apparatus, lysosomes, vacuoles and microbodies. …

Not every structure in a eukaryotic cell is enclosed by a membrane, and the ones that are can be wrapped in either one layer or two, which gives a natural way to group them.

Ribosomes stand apart from other organelles precisely because they have no surrounding membrane at all — they are simply a compact particle built from RNA and protein. The centriole, with its cartwheel-like arrangement of tubulin triplets, is likewise not enclosed by a membrane.

A larger group of organelles is bound by a single membrane. This includes the endoplasmic reticulum, which forms a network of tubules and cisternae; the Golgi apparatus, made of stacked, flattened sacs; lysosomes, small vesicles rich in hydrolytic enzymes; vacuoles, enclosed by the tonoplast; and microbodies, the tiny enzyme-containing vesicles found in both plant and animal cells. …

Method: Sort Organelles Using One Consistent Criterion at a Time

The question gives you the sorting rule up front — membrane count (zero, one, or two) — so the discipline required here is to apply that single criterion consistently to every organelle you know, rather than grouping organelles by "how important" or "how big" they feel, which is a common way students accidentally misplace items.

A reliable way to work through this is to first list every organelle you can recall from the chapter, then ask of each one, individually: "does this have a membrane wrapped around it at all?" If no, it goes in the unbound group (this is a short list — mainly ribosomes and the centriole, since both are built from protein/RNA or protein subunits with no lipid boundary). If yes, ask a second question: "is there one continuous membrane, or two separate ones creating an inner and outer compartment?" A single continuous membrane puts an organelle in the middle group (ER, Golgi apparatus, lysosomes, vacuoles, microbodies); two distinct membranes (with a gap or space …