Cell Theory, Form, and Function

Prokaryotes and Eukaryotes

Two structurally distinct types of cells have evolved that vary greatly in their internal complexity. Prokaryote cells are the simplest type and are evolutionary precursors to eukaryote cell types. What is thought to be the earliest known fossilized cells were discovered by paleontologists working near the Great Lakes in North America. They discovered microfossil evidence with enough detail to classify the cells as prokaryote. How did they know they were prokaryote?

Although both prokaryote and eukaryote cells can have a cell wall and a cell membrane to enclose the cellular cytoplasm, the structural similarities end there. Inside a typical prokaryote cell, such as a bacteria cell, there are no membrane-bound organelles. An organelle is a subcellular structure that has a specific function. Even the genetic material, although often contained and cornered inside the cell, is not bound by a membrane. Eukaryotic cells, which basically include every cell type except bacteria, are characterized by internal organelles surrounded by a membrane, which helps to increase their organization and efficiency. In contrast to prokaryotes, in eukaryotes the chromosomes are made of distinct lengths of DNA and are stored within a nuclear membrane. Because prokaryotes are simpler, lacking membrane-bound organelles, they are also much smaller (1 to 10 micrometers) than eukaryotes, which range from 10 to 100 micrometers in size.

book cover

Excerpted from The Complete Idiot's Guide to Biology © 2004 by Glen E. Moulton, Ed.D.. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc.

To order this book direct from the publisher, visit the Penguin USA website or call 1-800-253-6476. You can also purchase this book at Amazon.com and Barnes & Noble.

highlights

Special Books for the Kids You Love
Celebrate 20 years of sharing love to the moon and back with the anniversary edition of Guess How Much I Love You, one of the world’s best-loved picture books. Plus, search our Book Finder for more great book picks. Brought to you by Candlewick Press.

Vote Now for the Children's & Teen Choice Book Awards
Voting is open now through May 3 for the Children's and Teen Choice Book Awards — the only national book awards program where the winning author, illustrator, and books of the year are selected by young readers. Encourage your child to vote for his favorites today!

Top 10 Math & Science Apps for Your Whiz Kid
Looking for the best math and science apps for kids? Check out these cool apps for all ages, which will grow your child's love of the STEM subjects (science, technology, engineering, and math).

Registered for Kindergarten — Now What?
Wondering what to do now that you've signed your child up for kindergarten? Try our award-winning Kindergarten Readiness app! This easy-to-use checklist comes with games and activities to help your child build essential skills for kindergarten. Download the Kindergarten Readiness app today!

stay connected

Sign up for our free email newsletters and receive the latest advice and information on all things parenting.

Enter your email address to sign up or manage your account.

Facebook icon Facebook icon Follow Us on Pinterest

editor’s picks