Procaryotic cell structure
Simple cells compared to eucaryotic structure – more primitive without a true nucleus.
Similar to eucaryotic cells; predominantly aqueous with ribosomes and nucleotide-protein complexes
Nuclear body/bacterial nucleoid:
• single long chromosome; double stranded DNA
• exists in a ‘supercoiled’ structure (~1mm in length if extended)
• may have additional fragments of DNA (episomal DNA) – often called plasmids
• consists of protein and RNA; smaller than eukaryotic cells
• concerned with protein synthesis
• as bacteria have limited cell organelles, the cell membrane carries out many of the functions
• 5-10nm thick; relatively weak
• consists mostly of phospholipids and proteins
• external to cell membrane; 10-25nm thick; relatively strong structure
• rigid structure that protects cell from rupture (high osmotic pressure in cell)
• porous and permeable to low molecular weight substances
• plays important role in cell division
• generally two types – gram positive and gram negative
Gram positive cell walls:
Less complex than gram negative. Has thick layer (15-80nm) of peptidoglycan (murein, mucopeptide) arranged on a rigid meshwork.
Gram negative cell walls:
Peptidoglycan layer is only 1-2nm. Has two membranes – outer lipoprotein layer and an inner cytoplasmic membrane seperated by the periplasmic space
Layer of extracellular gelatinous material, mostly polysaccharides.
Function to help bacteria adhere to tissues and resist ingestion by phagocytosis
Long threadlike appendages made up of the protein, flagellin.
Allow motility of bacteria by rotation
Filamentous appendages on many bacteria that extrude from the cytoplasmic membrane
Composed of the protien, pilin
Formation of spores is how some microorganisms survive harsh environmental conditions
Genetic material of cells is concentrated and surrounded by a protective coat becomes very resistant to desiccation, heat and many chemical agents.
Spores are biochemically inert