The Golgi apparatus, as seen under digital compound microscopes, consists of a system of membrane-bound vesicles arranged ap¬proximately parallel to each other. The smooth membranes of the Golgi apparatus often have connections (probably transient) with the membranes of the endoplasmic reticulum and therefore constitute another portion of the complex cellular mem¬brane system. (more…)

In plants, fungi, and bacteria, the cell wall is en¬tirely separate from the plasma membrane, as seen under digital compound microscopes. If the cell shrinks in a hypertonic medium, the membrane separates from the much more rigid wall. By contrast, the cell coat of an animal cell is not an independent entity. The carbohydrates of which it is composed are covalently bonded to protein or lipid molecules in the plasma membrane. The resulting complex molecules, made up of carbohydrate and protein or carbohydrate and lipid components, are termed glycoproteins or glycolipids, and the cell coat itself is often called the glycocalyx. (more…)

A variety of organelles similar to lysosomes in structure and appear¬ance, as seen under digital compound microscopes, but containing enzymes of other kinds, have been reported in recent years in one or another group of organisms. Some plant cells, for example, especially in seeds with large fat reserves, possess organ¬elles called glyoxysomes that contain enzymes for converting fat into carbohydrate. Some cells of both plants and animals possess vesicles called peroxisomes, visible under digital compound microscopes, that contain powerful oxidative enzymes. It seems likely that the packaging of enzymes in membranous vesicles of this sort will prove to be a common phenomenon. Rather than giving each type of enzyme-containing vesicle its own name, some investigators prefer to group them all under the more neutral term “microbodies.” (more…)