Lecture 2 Structure,physiology And Biochemistry Of Microorganisms Flashcards
Cell theory
Cell is the basic structural and functional unit of all living organisms and it is the smallest form of life and all cells come from pre-existing cells
Prokaryotic vs eukaryotic
Methods of reproduction by cell division,cell binary fission and mitosis and meiosis
It’s present of DNA and RNA for protein synthesis
Cellular metabolism organised in specific metabolic pathways
They respond to external and internal stimuli to changes in the retune and PH and nutrient levels
The difference between prokaryotic and eukaryotic
Prokaryotic cells have no nucleus no membrane bound cell organelles
Eukaryotic cells have nucleus ad no membrane bound cell organelles
Glycocalyx
It is he extra cellular matrix that surrounds cells
Normally a network of polysaccharides but the composition varies
Its function:
Cell to cell communication
Binding of cells to the extra cellular matrix
Protection from pathogens
Modulation of the immune response
Attachments site for bacteria to insert surfaces which is the formation of biofilms
Cell wall
Bacteria archaea fungi plants and algae typically have cell walls but into animal cells.different chemical composition and this can be used to differentiate between organisms.
The cell wall protects the interior of cells from physical movements and hostile environments and it contributes too the shape of the organism.
Archaea: cell wall does not contain peptidoglycon some contain pseudopeptidoglycan
Plant cells: polysaccharides mostly cellulose hemicellulose and pectin.
Algae: cellulose and a vary of glycoproteins polysaccharide inclusions used in algal taxonomy
Fungi: cellulose glucosamine and chitin not all fungi have cell walls
Bacterial cell wall
Bacteria is identified in two ways either gram positive and gram negative by staining.
The differences in the cell wall composition are important in selecting the appropriate anti microbial drug.
Gram positive v/s Gram negative cell wall
Gram positive:
Thick peptidoglycan layer
External to the plasma membrane
Contains tieichoic acid and lipoteiichoic acid
Periplasmic space between plasma membrane cell wall-minimal
Easily treated produces exotoxins
Gram negative:
Thin peptiddoglycan layer
More complex
Outer membrane that provides and is anchored to the lipoprotein molecules of the peptidoglycan layer
The outer membrane is similar to plasma membrane
Lipopolysaccharides produce exo/endotoxins
Surface appendages
Present in both prokaryotic and eukaryotic cells
Prokaryotes have flagella and pili (fimbriae)
The piliiii is more rigid and shorter than flagella and it is composed of protein-piliin its movement is adhesion twitching and conjugation
Eukaryotes: consist if Celia,micrviilii,flagella
The microvilli is known for membrane extension and movements such as absorption secretion and adhesion and motility
The cilia and the eukaryotic flagella are structurally the same but they are shorter in movements on surface and flagella are longer and move the whole cell.move fluid over the surface goblet cells secretions
Flagellum
Bacterial flagellum are long helical filaments about 12-30 nm in diameter used for movement ini the environment.
Protein components are flagella is assembled to from a cylindrical structure with a hollow core
Long filament external to the cell crusade
Has a hook located at the ed of the filament
Basal body to which hook is anchored
Basal body consists of. Rod and one or two pairs of disics
Types of bacterial flagella
Monotrichous:single polar structure at one end of the bacterium
Lophotochoius:flagella ini tufts at one or both ndsamphiitriichoud:single polar structure at each of the ends
Peritrichous:flagella distributed over the general surface
The movement of bacteria
The flagella can either move the Astoria clockwise or counterclockwise
Movement can be either away or towards a stimulus is called taxis
Rotation depends on cells energy
Results in various patterns of motility either runs(swims) or tumbles
Organisation:biofilms
Its a collection of surface associated microbes and it is enclosed by extracellular mostly polysaccharides matrix.
Can include non-cellular material mineral crystals,corrosive particles blood and other substances
First colony adheres to surface ad anchor permanently if not removed immediately new incoming cells then attach
Biofilms grows through cell division and recruitment cells behaviour changes with thickness of the film
They form on a variety of surfaces including medical surfaces and aquatic systems etc.
The disadvantage if biofilms is that it causes I concern in food industry cleansers are being send on surfaces will kill isiinle cells.
Biofilms provide ideal environment for plasmid exchange
The positive use is the bioremediation of contaminated soil or water
Cell organelles
Chloroplasts: found in plans and algae the inner membrane I of chloroplast contain is pigments called chlorophyll and enzymes
The stroma contains mall circular DNA
The chloroplast converts sun energy into chemical energy photosynthesises
Vacuoles: membrane bound storage
The contractive vacuoles in protozoans pumps excess water out of the cell
Inclusion(both)
Mono layer which has the storage and the gas inclusion which allows the bacteria to float
Ribosomes:contain ribosomal and RNA the production of protein is for cell maintenance and repair.
Membrane transport mechanisms
Passive transport: no cellular energy needed and it has molecular Brownian movement across the concentration gradient
Active transport:requires cellular energy and it goes against the concentration gradient
