Download Prokaryotic and Eukaryotic Cells

Prokaryotic and Eukaryotic Cells
Definition: Cells are the basic units that compose all living organisms. All cells possess three
fundamental features: 1) cells contain a plasma membrane that separates them from the
surrounding environment; 2) cells possess regions where DNA is located; and 3) cells contain
cytoplasm. There are two major cell types: prokaryotes and eukaryotes.
Prokaryotes
• Classified within the kingdoms Bacteria and Archaea
• Classified as simple, single-celled organisms
• Typically small (fewer than 2 micrometers in diameter)
• Do not possess a true nucleus
• In lieu of a nucleus, prokaryotes have a nucleoid region consisting of RNA, DNA, and
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protein
Multiply through binary fission; cells do not undergo meiosis or mitosis
Utilize transformation, transduction, and conjugation as means of creating new
genomes
• Transformation • Transpires when a cell uptakes naked DNA material secreted from live bacteria or
released from dead bacteria
• Transduction • The transfer of DNA from one bacterium to another via a virus
• A virus destroys the host cell (bacterium 1) and incorporates some of the bacterial
genes into its viral genome
• The virus then replicates, and some of the viral progeny contain the original host
DNA from bacterium 1
• The progeny then infect another bacterium (bacterium 2) and inject some of the
original host DNA (from bacterium 1), along with viral DNA, into bacterium 2
• Conjugation
• Takes place between a donor (which must possess a conjugative plasmid) and a
recipient bacterium
• The donor bacterium initiates contact with the recipient via a sex pilus, allowing
for cell-to-cell contact and the transfer of DNA
• Plasmids frequently contain genes that encode for toxin production, antibiotic
resistance, and virulence factors • Plasmids are circular, double-stranded DNA molecules that are located
extrachromosomally in some prokaryotic cells
• Plasmids are not typically necessary for a cell to flourish, however, plasmids are
generally comprised of genes that allow for a selective advantage
Cell walls are found in the majority of prokaryotes, however, the composition differs
between Bacteria and Archaea
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Prokaryotic and Eukaryotic Cells
• Peptidoglycan is found within the cell walls of bacteria; peptidoglycan is a target site
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for many antibiotics such as penicillin, which were created to disrupt cell wall
synthesis
Lack mitochondria
Lack chloroplasts
May possess endospores
Possesses 50S and 30S ribosomal subunits
Eukaryotes
• Classified within the kingdoms Protista, Fungi, Animalia, and Plantae (and include
algae)
• Cells are complex and surrounded by a plasma membrane
• Cells are typically larger than prokaryotic cells, measuring between 2 and 100
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micrometers in diameter
Cells possess membrane-bound organelles
Contain a nucleus that is encapsulated by a nuclear envelope
Cells can divide via mitosis
New genomes are created via sexual reproduction
Eukaryotic ribosomes consist of a small (40S) and a large (60S) subunit, except for
mitochondria which possess 30S and 50S subunits
Do not contain plasmids
Lack endospores
Cell walls are present in algae, plants, and fungi, but are absent in animal and most
protozoan cells; however, the cell walls do not contain peptidoglycan
Chloroplasts are present in algae and plants
Cells possess a cytoskeleton which includes microtubules for structural support
Reference
Madigan M, Martinko J, Parker J. Brock biology of microorganisms. 9th ed. Upper Saddle
River, NJ: Prentice-Hall (Pearson); 2000. 6-9; 57-71; 99-100.
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