Learning Objectives: To be able to describe characteristics of bacteria and the functions of each structure
What can you remember? ALL bacteria are prokaryotes. What does this mean?ALL bacteria are prokaryotes. What does this mean? Without nucleusWithout nucleus Compare prokaryotes and eukaryotes:Compare prokaryotes and eukaryotes: ProkaryotesEukaryotes Small – less than 5 µm Always unicellular No nucleus or any membrane bound organelles DNA is circular, without proteins Ribosomes are small (70S) No cytoskeleton Motility by rigid rotating flagellum Cell division by binary fision Reproduction is always asexual Huge variety of metabolic pathways Large cells (>10 µm) Often multicellular Always have a nucleus and other membrane bound organelles Ribosomes are large (80S) DNA is linear and associated with proteins to form chromatin Always has a cytoskeleton Motility by flexible waving undulipodium made of tubilin Cell division by mitosis or meiosis Reproduction is sexual or asexual Common metabolic pathways
How big? A metre (m) contains an thousand millimetres (mm)A metre (m) contains an thousand millimetres (mm) A millimetre contains a thousand micrometres (µm)A millimetre contains a thousand micrometres (µm) A micrometre contains a thousand nanometres (nm)A micrometre contains a thousand nanometres (nm) The size of an animal cell and some of its contents, in micrometres and nanometres is given below.The size of an animal cell and some of its contents, in micrometres and nanometres is given below. Animal cell 20µm; mitochondrion 1µm; cell membrane (width) 8nm; nucleus 5µm; ribosome 15nm Imagine an animal cell is 5 metres across. How big would the various organelles inside it be? Real animal cell = 20µm. 5 metres = 5000 000µm, so the cell has been magnified 5000 000/20 = 250 000 –Size of nucleus 5 µm x 250 000 = 1.25m 5 µm x 250 000 = 1.25m –Size of mitochondria 1 µm x 250 000 = 250 mm 1 µm x 250 000 = 250 mm –Size of ribosome 15nm x 250 000 = 3.75mm 15nm x 250 000 = 3.75mm –Width of cell membrane 8nm x 250 000 = 2mm 8nm x 250 000 = 2mm
Bacteria are classified according to their shape: Make a list of the shapes of bacteria that you can remember
Cocci – spherical bacteria: Cocci – smallest bacteria, occur as single spheres. Diplococci – pairs of spheres, e.g. Diplococcus pneumoniae (pneumonia). Staphylococci – clusters of spheres, e.g. Staphylococcus aureus (boils and food poisoning). Streptococci – chains of spheres, e.g. Streptococcus pyogenes (sore throats).
Bacilli – rod-shaped bacteria: Individual rods – e.g. Escherichia coli, Salmonella typhi (typhoid fever). Chains of rods – e.g. Azotobacter, Bacillus anthracis (anthrax).
Spirilla – large, spiral-shaped bacteria (motile with flagella), e.g. Treponema pallidum (causes syphilis).
StructureFunction RibosomesCarries out protein synthesis MesosomeSite of respiration (formed by the intucking of the plasma membrane) Slime CapsulePhysical barrier to predatory protazoa, white blood cells or bacteriophages Cell WallProvides structure FlagellumOrganelle of propulsion Pili or FimbriaeBristle like projections that allow bacteria to stick to surfaces Cell surface membrane Barrier between cell and environment Regulates transport of substances PlasmidLoops carrying 10-30 genes enable production of antibiotics, or resistance to antibiotics Nuclear material within the nuclear zone Carries genetic material
Give four features that most bacteria have in common –C–C–C–Cell wall made of peptidoglycan –R–R–R–Reproduce asexually by binary fission –N–N–N–No membrane bound organelles –D–D–D–DNA is a circular molecule Give three features that are only present in some bacteria –P–P–P–Presence of flagella –M–M–M–Mesosomes –P–P–P–Pili or fimbriae –S–S–S–Slime layer or capsule The mitochondria found in eukaryotic cells contain their own loop of DNA as well as 70S ribosomes. Given this information suggest how mitochondria may have originated