Cellular Basics

Structures Inside Cells

What are the major components of the eukaryotic cell?

The virus that causes chicken pox can cause the human body to produce memory cells: After having the chicken pox once, a re-exposure to the virus is fought off by the memory cells, preventing a person from contracting the disease more than once. But in this case, you may not get the “chicken pox,” but another problem: After a chicken pox infection, the virus remains dormant in the body’s nerve tissues. While the immune system keeps the virus at bay, later in life—usually as an adult—the virus (it is called herpes zoster, from the varicella zoster virus) can reactivate (although the reason is unknown, it is often traced to stress or a suppressed autoimmune system). This causes a different form of the viral infection called shingles—which leaves a person with an often painful skin rash.

Many major components in eukaryotic cells exist, all of various sizes and functions. The following table lists the major structures in the cell nucleus, the cytoplasmic organelles, and the cytoskeleton (for both animals and plants):



Cell Nucleus




Large structure surrounded by double membrane



Special body within nucleus; consists of RNA and protein



Composed of a complex of DNA and protein known as chromatin; resemble rodlike structures after cell division

Cytoplasmic Organelles



Plasma membrane

Membrane boundary of living cell



Network of internal membranes extending through reticulum (E.R.) cytoplasm


Smooth endoplasmic

Lacks ribosomes on the outer surface reticulum


Rough endoplasmic

Ribosomes stud outer surface reticulum



Granules composed of RNA and protein; some attached to E.R. and some are free in cytosol


Golgi apparatus

Stacks of flattened membrane sacs



Membranous sacs (in animals)



Membranous sacs (mostly in plants, fungi, and algae)


Microbodies (e.g., peroxisomes)

Membranous sacs containing a variety of enzymes



Sacs consisting of two membranes; inner membrane is folded to form cristae and encloses matrix


Plastids (e.g., chloroplasts)

Double membrane structure enclosing internal thylakoid membranes; chloroplasts contain chlorophyll in thylakoid membranes

The Cytoskeleton




Hollow tubes made of subunits of tubulin protein



Solid, rodlike structures consisting of actin protein



Pair of hollow cylinders located near center of cell; each centriole consists of nine microtubule triplets



Relatively short projections extending from surface of cell; covered by plasma membrane; made of two central and nine peripheral microtubules



Long projections made of two central and nine peripheral microtubules; extend from surface of cell; covered by plasma membrane


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