micro week 3 chptr 4
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How are Prokaryotes Different from Eukaryotes?
- The way their DNA is packaged
- –No nucleus
- –Not wrapped around histones
- The makeup of their cell wall
- –Bacteria- peptidoglycan
- -Archae- tough and made of other chemicals, distinct to them
- Their internal structures
- –No complex, membrane-bound organelles
Prokaryotic Form and Function
What are the external parts of a prokaryote?
- Appendages- Flagella, Pili, Fimbriae
- Glycocalyx - capsule, slime layer
what are the cell envelope parts of a prokaryote?
what are the parts of the internal prokaryote (6)?
- actin cytoskeleton
Structures Common to all Bacterial Cells
- •Cell membrane
- •One (or a few) chromosomes
- Structures found in most bacterial cells:
- •Cell wall
- •Surface coating or glycocalyx
Structures found in some bacterial cells
- •Slime layers
- •Actin cytoskeleton
External structures of prokeyotes
are appendages present on all species?
can provide what?
which can be used for attachment and mating?
- cell extentions
- no but are common
- motility (flagella and axial filiments)
- pili and fimbriae
what are the 3 parts of prokaryote flagella?
describe polar arrangment of flagella?
flagella attached at one or both ends of the cell
small bunches or tufts of flagella emerging from the same site
dispersed randomly over the structure of the cell
a single flagellum at either end of the cell
move toward or away from stimuli
axial filaments are also known as?
periplasmic flagella or endoflagella
where is axial filaments enclosed?
in the space between the cell wall and the cell membrane
rotation of the axial filiments cause what?
cell to move
describe the physical characteristics of Pili?
Elongate, rigid tubular structures, hollow
what are Pili made of?
where are pili found?
gram negative bacteria
what are pili used in?
conjugation - a process to transfer DNA from one cell to another
fimbriae allow bacteria to do what? why is this important?
- stick to surfaces and each other
- important for reproduction
glycocalyx consist of what?
polysaccharides and protiens
glycocalyx protect the cell from what?
how do glycocalyx differ from bacteria
- chemicle composition
glycocalyx are formed by?
many pathogenic bacteria- protect the bacteria from phagocytes
glycocalyx are important in formation of what?
majority of bacteria have cell envelope where does it lie?
the cell membrane is composed of?
2-3 basic layers
what are the 2-3 basic layers of the cell envelope?
- cell wall
- cell membrane
- in some bacteria, the outer membrane
how many layers does gram positive bacteria have? what about gram negative?
- gram pos - 2 layers
- gram neg - 3 layers
what are gram positive bacteria consist of? what about gram negative?
- gram pos - cell wall and cytoplasmic membrane
- gram neg - outer membrane, cell wall, and cytoplasmic membrane
what does the structure of the cell wall help to determine?
the shape of a bacterium
cell walls of bacterium are strong and rigid because the contain what?
the structure of the cell wall prevents what?
cell walls are targeted by what?
many antibiotics they have little protection from lysis
Gram-positive cell wall characteristics:
- A thick (20 to 80 nm), homogeneous sheath of peptidoglycan
- Contains tightly bound acidic polysaccharides
characteristics of Gram-Negative Cell Wall
- Single, thin (1 to 3 nm) sheet of peptidoglycan
- Periplasmic space surrounds the peptidoglycan
Some bacteria aren’t characterized as either gram-positive or gram-negative
Some don’t have a cell wall at all. what is an example?
Archae- unusual and chemically distinct cell walls
gram negative outer membrane are similar to the cell membrane exept for containing what to things?
specialized polysaccharides and proteins
what does the uppermost layer of gram-negative bacteria contain?
phospholipid layer anchored by lipoproteins to the peptidoglycan layer below
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