Basic Biology


What are the major components of the eukaryotic cell?

Structure Description
Cell Nucleus
Nucleus Large structure surrounded by double membrane
Nucleolus Special body within nucleus; consists of RNA and protein
Chromosomes Composed of a complex of DNA and protein known as chromatin; resemble rodlike structures after cell division
Structure Cytoplasmic Organelles
Plasma membrane Membrane boundary of living cell
Endoplasmic reticulum (ER) Network of internal membranes extending through cytoplasm
Smooth endoplasmic reticulum Lacks ribosomes on the outer surface
Rough endoplasmi reticulum Ribosomes stud outer surface
Ribosomes Granules composed of RNA and protein; some attached to ER and some are free in cytosol
Golgi complex Stacks of flattened membrane sacs
Lysosomes Membranous sacs (in animals)
Vacuoles Membranous sacs (mostly in plants, fungi, and algae)
Microbodies (e.g., peroxisomes) Membranous sacs containing a variety of enzymes
Mitochondria 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
Microtubules Hollow tubes made of subunits of tubulin protein
Microfilaments Solid, rod-like structures consisting of actin protein
Centrioles Pair of hollow cylinders located near center of cell; each centriole consists of nine microtubule triplets (9 × 3 structure)
Cilia Relatively short projections extending from surface of cell; covered by plasma membrane; made of two central and nine peripheral microtubules (9 2 structure)
Flagella Long projections made of two central and nine peripheral microtubules (9 2 structure); extend from surface of cell; covered by plasma membrane


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