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Author: Jessica Libby

  • Examine the structural, functional, nutritional, metabolic and genetic adaptations of prokaryotic organisms.
  • Compare and contrast the Domain Bacteria to the Domain Archaea.
  • Discuss the role of prokaryotes in the bioshpere.
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Reading Assignment

Please read chapter 19 of the book. 


Source: Campbell Biology 10th edition

Prokaryotic v. Eukaryotic Cells

One of the largest differences between these two types of cells is that prokaryotic cells do not have membrane bound organelles (nucleus, endoplasmic reticulum, mitochondria, etc.) like eukaryotic cells.  Also, the DNA of eukaryotic cells is linear whereas the DNA of prokaryotes is circular and there is only 1/1000 the amount of DNA. 



Prokaryotic Cells

A quick description of cell structure by Brightstorm.

Bacterial Kingdom

A video showing the difference between bacteria and archaea by Brightstorm.

Structure and Function

Prokaryotes are divided into two domains of life: Bacteria and Archaea. The vast majority of these individuals have a cell wall. The cell wall of bacteria is made of peptidoglycan while the cell wall of archaea is made from polysaccharides and proteins. The major purposes of the cell wall is for protection and to prevent the cell from losing an excess of water. If the cell loses too much water reproduction is inhibited. Many prokaryotes have capsules over their cell wall which is typically a sticky layer of either polysaccharides or protein.  This capsule allows them to stick to others in their colony as well as the substrate. There are some prokaryotes that use pili or fimbriae (shorter and more numerous) to stick to their substrate.  Half of the prokaryotes have flagella which allow them to move.  

Many prokaryotes reproduce by binary fission.  There are some bacteria that are able to form endospores when nutrients are low.  These bacteria copy their chromosomes and cover it with a tough wall, or endosore. The endospore is capable of surviving boiling water and when the environmental conditions are right, the bacteria will begin reproduction again.

There is a lot of nutritional diversity among prokaryotes based on how they obtain both carbon and energy.


















Prokaryotes also differ in how they obtain oxygen. Obligate aerobes use oxygen for cellular respiration.  Faculative anaerobes use oxygen if it is present but are able to grow by fermentation if it is not.  Obligate anaerobes are poisoned by oxygen and either live off fermentation or use other chemicals (nitrate ions, sulfate ions) to get energy from anaerobic respiration.  


This is a lecture on the different types of bacteria from Khanacademy.