4. Features of prokaryotes Flashcards
1
Q
how are prokaryotic cells organised?
A
- cell envelope
- cytoplasm
- appendages
2
Q
what is the cell envelope
A
- glycocalyx
- cell wall
- cell membrane
3
Q
what is the cytoplasm
A
- genetic info [
– chromosome
–plasmids - ribosomes
- specialised features
4
Q
what appendages do prokaryotes have
A
- sex pilus
– stabilises mating bacteria during DNA tranfer by conjugation - flagella
– swimming movement - fimbriae
– attatchment to surfaces
– protection againts phagotrophic engulfment
5
Q
what is the structure of the glycocalyx
A
- slime layer
– loosely adherent
– nonuniform density / thickness - capsule
– condensed layer closely surrounding bacterium - both
– form glycocalyx
– can exist as either
– very important in biofilm formation
6
Q
what is the structure of the cell wall
A
- gram positive
- gram negative
- large complex peptidoglycan molecule
– disaccharide polymer (murein)
7
Q
what is peptidoglycan
A
- disaccharide polymer
–murein - polymer made of sugars and amino acids
– glycopeptide
-that forms mesh-layer outside plasma membrane of bacteria
– not archaea) - sugar consists of NAG (N-acetylglucosamine) and NAM (N-acetylmuramic acid) units
– attached to NAM is peptide chain (3-5 amino acids)
8
Q
what is a gram -ve cell?
A
- thin layer of peptidoglycan
– in periplasmic space (between inner and outer lipid membranes - small lipoproteins embedded in outer membrane covalently bound to peptidoglycan
- lipopolysaccharides on outer leaflet
– complex molecules adhesive in nature - porins / specialised transporters
– act as channels to facilitate non-vesicle mediated transport
9
Q
what is a gram +ve cell
A
- single lipid membrane surrounded by cell wall
– thick layer of peptidoglycan
– and lipoteichoic acid
– anchored to cell membrane by diacylglycerol - thick (40-80% of cell dry weight)
- lipoteichoic acid links to plasma membrane
– immune response - lipoteichoic acid links to peptidoglycan
– rigidity of cell wall
10
Q
what are the functions of the cell wall
A
- structural strength of cell
- maintaine cell chape (cell growth, reproduction, nutrients, movement)
- protection from cell lysis
- keep out toxic molecules
- (pathogens): contribute to pathogenicity of certain microorganisms
11
Q
what is the cell membrane
A
- lies beneath cell wall
– encompasses cytoplasm - highly selectively permeable barrier
– regulates passage of substances in/out
– passage of water/uncharged molecules - bacterial similar to eukaryotes
12
Q
what is the structure of archaea membranes
A
- saturated
- branched
- repeating isoprenoud subunits
– attach to glycerol (ester linkages in glycerides of eukaryotic/bacterial membrane lipids) - useful for adaption and survival in extreme environments
13
Q
what are the functins of the cytoplamsic membrane
A
- osmotic / permeability barrier
- locations of transport systems
– for specific solutes (nutrients/ions) - energy generation fxns
– respiratory / photosynthetic elecctron transport systems - synthesis of membrane lipids
– lipopolysaccharides (gr. -ve) - synthesis of murein
– peptidoglycan - assembly / secretion
– extracytoplasmic proteins - co-ordination of DNA replication / segregation
– septum formations
– cell division - chemotaxis
– motility
– sensing fxns - location of specialised enzyme system
14
Q
what is the periplasm
A
- between inner and outer membranes
– Gram -ve bacteria - contains enzymes
– cell wall / membrane component assembly - various degradative or detoxifying enzymes
- secretion systems
- sensing proteins
– chemotaxis
– signal transduction - binding proteins
– for solutes take up by BPDT transport systems
15
Q
what is the structure of the cytoplasm
A
- internal matrix of cells
- appears homogenous
– highly organised/packed with ribosomes - 70% water
- macromolecules
– proteins
– lipids
– polysaccharides
– nucleic acids
