Bacterial Cell Structure Flashcards
Functions of the cell wall:
1.Determines the cell shape
2.Prevent osmotic lysis
3.part of cell envelope
Cell wall structure
1- Made up of peptidoglycans
2- linked by polypeptides
3-Polymer of disaccharides
Q. What are the two types of cell wall
Gram+ve
Gram -ve
Q. Why does a gram -ve cell wall turn colourless once we add alcohol
Because the peptidoglycan layer is thinner than in gram+ve cell wall.
Gram Positive Cell walls
1.Thick peptidoglycan
2.No periplasm
3. No outer cell membrane
4. Teichoic acids
Gram Negative Cell Wall
1.Thin peptidoglycan
2. Periplasm
3.Outer cell membrane
4. No Teichoic acid
Q. We can’t do a gram test on mycoplasmas ?
as it contains sterols and a complete cell wall
Q. What is the clinical importance of cell wall?
lipopolysaccharides secretes endotoxins in gram negative bacteria
Lipopolysacchrides
Lipid A
The rigidity and shape of the bacterial cell is due to:
lipopolysacchride
Which substance of the membrane of gram-negative bacteria is a potent endotoxin?
Lipopolysacchride
Glycocalyx
A network of polysacchrides that project from cellular surfaces
Glycocalyx consists of :
1-A gelatinous capsule
2-A slimy layer
Function of GLycocalx
protects bacterium from harmful pathogens
Which of the following is the most important structure related to microbial attachment to
cells?
Glycocalyx
Structure of Bacterial Flagella
outside cell wall made up of flagellin attached by a protein hook anchored to the wall of the membrane by the basal body
Function of Flagella
motility
Pili and Fimbirae
Filamentous appendages that are shorter, straighter and more numerous than flagella
Pili and Fimbriae are found in
Gram -ve Bacteria
Fimbriae function
allow attachment
Pili Function
Transfer DNA from one cell to another
Prokaryotic cells have:
no true nuclei
Endospores are only found in two shapes
1-Bacillus
2-Clostiridium
Germination of endospores
Return to vegetative state
Endospores are resistant to :
1-Dissection
2-heat
3-chemicals
Endospores are:
Resting cells
Main difference between Flagella and Cilia:
Flagella : Taller
Cilia : Shorter
80S ribosomes
1-Membrane bound
2-Free
3- Attached to the ER in cytoplasm
70S Ribosomes
Found in chloroplasts and mitochondria
Prokaryotes
1-1 circular chromosome
2- No histones
3- Reproduce by BInary Fission
4- No organelles
5- Peptidoglycan cell walls
6- chromosomes not in a membrane
Eukaryotes
1- Paired chromosomes
2- chromosomes are in nuclear membrane
3- organelles
4-histones
5- Mitotic spindle
6- polysacchraide cell walls
