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Questions and Answers
What is the main purpose of the bacterial cell wall?
What is the main purpose of the bacterial cell wall?
- To store nutrients for the bacteria
- To regulate osmotic pressure within the cell
- To maintain the shape of the cell (correct)
- To produce energy through oxidative phosphorylation
What is the composition of the Gram positive bacterial cell wall peptidoglycan layer?
What is the composition of the Gram positive bacterial cell wall peptidoglycan layer?
- N-acetyl muramic acid and N-acetyl glucosamine (correct)
- Cholesterol and phospholipids
- N-acetyl glucosamine only
- Proteins and lipids
Where are teichoic acids located in bacterial cell walls?
Where are teichoic acids located in bacterial cell walls?
- Attached to the ribosomes
- In the outer layer of Gram positive cell walls (correct)
- In the cytoplasmic membrane
- In the inner layer of Gram negative cell walls
Which molecules are responsible for cross-linking in the peptidoglycan layer of the cell wall?
Which molecules are responsible for cross-linking in the peptidoglycan layer of the cell wall?
What is the significance of the thick peptidoglycan layer in Gram positive bacteria?
What is the significance of the thick peptidoglycan layer in Gram positive bacteria?
Why is digestion necessary for large molecules in bacterial cells?
Why is digestion necessary for large molecules in bacterial cells?
Why can't Mycobacteria be gram stained?
Why can't Mycobacteria be gram stained?
Why are wall-less bacteria often produced when treated with lysozyme or antibiotics that interfere with peptidoglycan biosynthesis?
Why are wall-less bacteria often produced when treated with lysozyme or antibiotics that interfere with peptidoglycan biosynthesis?
Which group of bacteria naturally lack a cell wall?
Which group of bacteria naturally lack a cell wall?
How does the lack of a rigid cell wall affect Mycoplasma?
How does the lack of a rigid cell wall affect Mycoplasma?
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Study Notes
Cell Wall Function
- Maintains the shape of the cell
- Supports the weak cytoplasmic membrane
- Plays a role in cell division
- Responsible for staining properties of the organisms
- Rigid and protects the cell from osmotic lysis
Gram Positive Cell Wall
- Thicker peptidoglycan layer compared to Gram negative bacteria
- Composed of alternating N-acetyl muramic acid and N-acetyl glucosamine
- Cross-linked by identical pentapeptides and tetrapeptides
- Site of action for penicillins, cephalosporins, and lysozyme enzyme
Teichoic Acids
- Polymers of glycerol phosphate or ribitol phosphate
- Located in the outer layer of Gram positive cell wall
Cell Wall of Gram Negative Bacteria
- Outer membrane, peptidoglycan, and periplasmic space
- Digestion is necessary for molecules to pass through the outer membrane or cell membrane
Acid-Fast Bacteria
- Mycobacteria have an unusual cell wall with high lipid content (fatty mycolic acids)
- Cannot be Gram stained due to high lipid content
Wall-Less Forms of Bacteria
- Mycoplasma: the only group of bacteria that exist naturally without a cell wall
- Lacking a rigid cell wall, resulting in no defined shape
- Resistant to antibiotics that destroy bacterial cell walls
Induced Wall-Less Forms
- Produced when bacteria are treated with enzymes that are lytic for the cell wall (e.g. lysozyme)
- Or when antibiotics interfere with peptidoglycan biosynthesis
- Usually generates non-viable organisms
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