17 Questions
What is the primary component that gives rigidity to the bacterial cell wall?
Peptidoglycan
In which type of bacteria does the murein (peptidoglycan) constitute almost 95% of the cell wall?
Gram-positive bacteria
Which enzyme can completely dissolve the cell wall of some Gram-positive bacteria?
Lysozyme
What is the main difference in the peptidoglycan layer between Gram-positive and Gram-negative bacteria?
Location in the cell wall
Which component is found in the matrix substances of some Gram-positive bacterial cell walls?
Teichoic acids
What is used to classify bacteria into either 'Gram positive' or 'Gram negative'?
'Peptidoglycan' composition
What is responsible for the rigidity of the bacterial cell wall?
Peptidoglycan
Which type of bacteria has a cell wall with a thick layer of peptidoglycan?
Gram-positive bacteria
What is the main difference in the cell wall composition between Gram-positive and Gram-negative bacteria?
Thickness of the peptidoglycan layer
Which staining method is used to differentiate between Gram-positive and Gram-negative bacteria based on their cell wall characteristics?
Gram staining
Which component of the bacterial cell wall is targeted by antibiotics like penicillins and cephalosporins?
Peptidoglycan synthesis
Which type of bacterial cell wall provides structural integrity to the cell?
Both Gram-positive and Gram-negative
What is responsible for the cell wall's inability to retain the crystal violet stain in Gram staining?
Peptidoglycan layer
Which component of the Gram-negative cell wall causes it to have an overall negative charge?
Lipopolysaccharides
What is the function of Lipopolysaccharides (LPS) present on Gram-negative cell walls?
Cause endotoxic activities
Which region of the Lipopolysaccharide (LPS) in Gram-negative cell walls determines the O antigen?
Polysaccharide
What form of shock does LPS Endotoxin cause due to its endotoxic activity?
Septic shock
Study Notes
Bacterial Cell Wall
- Peptidoglycan (Mucopeptide) is a unique component of bacterial cell walls, composed of alternating chains of N-Acetyl Glucoseamine and N-Acetyl Muramic acid, cross-linked by peptide chains.
- Peptidoglycan structure is responsible for the rigidity of the bacterial cell wall and determination of cell shape.
Gram Positive vs Gram Negative Bacteria
- Gram positive bacteria have peptidoglycans as the main structural element, making up nearly 95% of the cell wall.
- Gram negative bacteria have a thinner peptidoglycan layer, adjacent to the cytoplasmic membrane.
Peptidoglycan Structure
- Peptidoglycans are made up of a polysaccharide backbone consisting of alternating N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG) residues in equal amounts.
- Lysozyme can dissolve the cell wall of some Gram-positive bacteria by attacking the bonds between GA and MA.
Cell Wall Function
- The primary function of the cell wall is to protect the cell from internal turgor pressure caused by higher concentrations of proteins and other molecules inside the cell compared to its external environment.
Antibiotics and Cell Wall Synthesis
- Antibiotics like penicillins and cephalosporins stop bacterial infections by interfering with cell wall synthesis, with no effects on human cells.
Cell Membrane
- The cell membrane is composed of 2 layers of phospholipids with polar heads and non-polar tails, allowing water, gases, and small molecules to move freely.
- Membrane proteins (peripheral and integral) float in the membrane, facilitating molecule transport in and out of the cell.
Lipopolysaccharides (LPS)
- LPS present on the Gram-negative cell wall consists of three regions: polysaccharide determining O antigen, core polysaccharide, and glycolipid portion/Lipid A.
- LPS is responsible for endotoxic activities and can cause Septic Shock, with no direct treatment available.
Test your knowledge about the structure of the bacterial cell wall, focusing on the unique composition of peptidoglycan. Learn about the role of peptidoglycan in providing rigidity to the cell wall and shaping bacterial cells. Explore the classification of bacteria into Gram positive and Gram negative based on their cell wall composition and staining properties.
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