sc246: m icrobiology unit 1 seminar. what do the terms prokaryotic and eukaryotic mean? what are...
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What do the terms Prokaryotic and Eukaryotic mean? What are some of the major differences between Prokaryotic and Eukaryotic cells?
PROKARYOTIC CELLS
Comparing Prokaryotic and Eukaryotic Cells Prokaryote comes from the Greek words for
prenucleus. Eukaryote comes from the Greek words for true
nucleus.
One (usually) circular chromosome, not in a membrane
No membrane-enclosed organelles
Peptidoglycan cell walls (usually)
Binary fission
PROKARYOTE EUKARYOTE
• Paired chromosomes, in nuclear membrane
• Organelles• Simple cell walls (IF
present)• Mitosis
From an evolutionary prospective, Prokaryotic cells are much less complex than Eukaryotic cells. It seems that we wouldn’t have much of a problem fighting them off, right? However, this is obviously not the case. Offer an explanation for this. WHY do you think we still get infections and illnesses?
What is the Gram stain, and why is it a fundamental part of identifying bacteria? What are the major differences between Gram negative and Gram positive cells?
GRAM STAIN
The Gram stain was developed by Christian Gram in 1884
Primary stain of identification in microbiology lab
Used to classify bacteria as either gram positive or gram negative
Most, but not all, bacteria can be stained using this method
Staining procedure:1.Crystal violet and Gram’s iodine: Primary stain2. Stain is decolorized with 95% ethanol3. Counterstain: Safranin4. Water rinse
Gram + retain CV and remain purpleGram – retain safranin
* Based on cell physiology
GRAM STAIN MECHANISM
Polymer of disaccharideN-acetylglucosamine (NAG) & N-acetylmuramic acid (NAM)
Linked by polypeptides
PEPTIDOGLYCAN
Figure 4.13a
Thick peptidoglycan
Teichoic acidsIn acid-fast
cells, contains mycolic acid
GRAM-POSITIVE CELL WALLS GRAM-NEGATIVE CELL WALLS
• Thin peptidoglycan
• No teichoic acids
• Outer membrane
Lipopolysaccharides, lipoproteins, phospholipids.
Forms the periplasm between the outer membrane and the plasma membrane.
Protection from phagocytes, complement, antibiotics.
O polysaccharide antigen, e.g., E. coli O157:H7.
Lipid A is an endotoxin.Porins (proteins) form channels through
membrane
GRAM-NEGATIVE OUTER MEMBRANE
The medical and scientific communities use their knowledge of Prokaryotic cells to target infectious microbes and clear out infections. Given just what you have learned so far, how do you think they might go about this?