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BIOL 2900 (72)
Dr Manafi (1)
Lecture 2

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York University
BIOL 2900
Dr Manafi

CELL STRUCTURE AND FUNCNTION Cell Structure Prokaryotes vs Eukaryotes Feature Prokaryotes Eukaryotes Nucleus NO YES RNA process NO YES Organelles NO YES Cell Wall YES Not in Animals STRUCTURE OF BACTERIA AND FUNCTION FLAGELLUM:  flagellum/flagella are a medium of locomotion. It allows the microbe’s to move. Some sort of engine for movements.  Structure:  long structure that extend beyond surface of cell  the flagella may be arrange differently depending on the species  many flagella can also be present  Function:  Movement: rotation propels bacterium through the environment  Used in chemotaxis – movement towards or away from the substance  Help the bacteria to detect the high concentration of some thing  Help bacteria to move away from the toxic substances AXIAL FILAMENTS:  Similar functions as flagella  Run lengthwise in all cells  A part of cell  Snake like movement FIMBRIA AND PILLI Fimbria:  Sticky projection, cover the bacteria body at all places  Used by bacteria to adhere to one another, to host , and to substance environment.  May be hundred per cell and are shorter than flagella  Gives affinity to hold on to the substance  Fimbrae may be evenly distubuted over the entire surface so that bacteria can use it according to need.  E Coli O157 – cause spinach infection and certain water problems Pilli  Long hollow tubes  Longer than fiberia but shorter than flagella  Bacteria typically only have one or more per cell  Join two bacteria cell and mediate the transfer of DNA from the one cell to another (conjugation) CAPSULE or SLIME LAYER  Sticky/sugar substance surrounding the outside of the cell  Almost always observed on the surface of cell growing in nature (as opposed to the laboratory)  provide protection against enviorenment  Eukaryotics cell eat bacteria as food  We have immune system that can catch the bacteria and digest it. For example: lysosomes  Composed of polysaccrides, polypeptides, glycproteins  Capsules: Thick layer a gel, firmly attached to cell surface  Slime Layer: thinner than capsule, loosely attached to cell surface.  Functions:  Mediate adherence of cell to each other and the surface  Protect bacteria cell from engulfment by neutrophills, macrophages, lysosomes,  Protect it from drying, keep it damp and alive  Reserve of carbohydrate (sugar) BIOFILM  It Is a single type of bacteria, accumulate together in one place to colonise  A biofilm is a complex aggregation of MO growing on a solid substrate  Mediated by fimbria and capsules  Much more resistant than planktonic cells to antimicrobial agents and host immune system  Help the bacteria to survive major attacks by antibiotics, because it is very resistant  In medicine, biofilm spreading along the implanted tubes or wires can lead to severe infection in patient.  Development of biofilm can make it difficult to treat the patient  They can be antibiotic resistant  Biofilm development is a process by which they make additions or subtraction. They count and form different types of bacterial strains that secret different toxins.  When population increases, they make different types of flagella thus make bacteria to move away and form biofilm on another place thus making it hard to treat the patient.  They come in contact with the surface  They produce the toxin and send message/ signals to other bacteria  Thus more bacteria are produced through fimberia – pilli CELL WALL  Cell wall allows the bacteria to resist osmotic stress  In hypotonic solution, bacteria will burst if they are without cell wall
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