Chapter 28, Problem S1.2BYB

Summary Introduction

To discuss:

The domains to which prokaryotes belong.

Introduction:

Prokaryotes are unicellular organisms that lack a well-defined nucleus and other membrane-bound organelles. They comprise the groups Archaea and Eubacteria and are included under Kingdom Monera.

The three-domain system was proposed by Carl Woese and is based on the studies of comparison of rRNA in organisms. Ribosomal RNA or rRNA is a key component of ribosomes and is highly conserved as the rate of mutation is low. Using this system, all organism was classified as Archaea, Bacteria, and Eukarya of which Eukarya is made of 4 kingdoms: Protista, Fungi, Plantae, and Animalia.

Explanation of Solution

The prokaryotes refer to organisms that lack a well-defined nucleus and other membrane-bound organelles. Hence, there are 2 domains in which the prokaryotes are classified: Archaea and Eubacteria, as both lack membrane-bound organelles and a nuclear envelope.

There are additional features present in these 2 domains of prokaryotes that are summarized as follows:

Feature	Archaea	Eubacteria
An amino acid that initiates translation.	Methionine	Formyl Methionine
Introns.	Present in some genes	Absent
Membrane lipids.	Branched	Unbranched
RNA polymerases.	Several	One
Cell wall peptidoglycan.	Absent	Present

Conclusion

The domains to which prokaryotes belong are Archaea and Eubacteria.