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Microbiology: The study of small life. All living things divided into 3 domains Eubacteria: prokaryotic cell structure Archaebacteria: prokaryotes, but different Eukaryotes: 4 kingdoms Plants, animals, fungi, and protists. What are microbiologists interested in?
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Microbiology: The study of small life • All living things divided into 3 domains • Eubacteria: prokaryotic cell structure • Archaebacteria: prokaryotes, but different • Eukaryotes: 4 kingdoms • Plants, animals, fungi, and protists. • What are microbiologists interested in? • Eubacteria and archaebacteria for sure. • Eukaryotes like fungi and protists • Animals (parasitic worms) but not really plants. • What’s missing? • VIRUSES!
What is “life”? • Cell theory: all living things are made of cells • Schleiden and Schwann, 1839 • Eukaryotes and prokaryotes: different kinds of cells • Excludes viruses, but we can argue later! • Living things organized into complex structures • We will compare prokaryotes and eukaryotes • Living things obtain energy / carry out chemistry • Bacteria are very diverse in how they do this! • Most bacteria of medical interest grow by aerobic metabolism or by fermentation (without oxygen) • Without energy source, bacteria don’t grow!
Life?- 2 • Living things are able to reproduce • All life comes from pre-existing life • Knowing when and how bacteria reproduce is important for controlling their growth. • All living things have DNA as a blueprint • Living things respond to their environment • Bacteria are small and simple in structure • They are successful because they can change themselves rapidly in response to their environment. • Bacteria tightly control which genes they use and when.
The study of chemistry (and biochemistry) is necessary to understand Microbiology Habitat Diet All living things are made of chemicals!
Atom: smallest unit of an elementElements differ by number of protons http://www.perceptions.couk.com/imgs/atom.gif
Molecule: atoms joined together with covalent bonds Electrons are shared between atoms. Covalent bonds are strong. When atoms in the molecule are of different elements, the substance is called a “compound”. http://www.truenorthgb.com/images/molecule.jpg
Covalent bonds & polar molecules Covalent Bonds: sharing of electrons between the oxygen and hydrogen atoms. Strong. Oxygen is an electron hog; the electrons spend more time there leaving the hydrogen’s proton nearly naked (and somewhat positive): Water is a polar molecule Water mdp2.phys.ucl.ac.uk/ Talks/Ice/Ice.html
Hydrogen bonds: • Electrical attraction between electronegative oxygen atom and nearly naked proton. • Bonds made between polar molecules. • Weak bonds.
H-bonds hold large molecules together Example: A-T base pair in DNA http://www.mun.ca/biology/scarr/Fg10_16a.gif
Hydrophilic and hydrophobic Surfaces made of molecules without polar groups (e.g. CH3CH2CH2CH2.) repel water.
H2O H+ + OH-[H+] = 10-7 pH= -log [H+] Logarithmic pH 7 is neutral Ranges from 0-14 Molecules that release H+ are acids; those that release OH- are bases. http://www.btinternet.com/~chemistry.diagrams/ph_scale.gif
The Chemicals of life are large and small • Cells contain molecules of all sizes but are MADE of large molecules called polymers • Polymer: a large molecule made of many similar or identical subunits. • “poly” means “many” (polyethylene, polysaccharide) • The small molecules that make up a polymer can be called “monomers” • “mono” means “one” • In our, not all polymers are biological • Plastics are all polymers too
Small molecules (monomers) and macromolecules (polymers) Ethylene and polyethylene
Four Classes of Biological Molecules • Carbohydrates • Sugars and their polymers • Nucleic acids and nucleotides • DNA, RNA, ATP • Lipids • Various hydrophobic molecules • Proteins and amino acids
Carbohydrates: CH2O Monosaccharides: glucose, fructose, many others Disaccharides: sucrose, lactose Oligosaccharides: found on glycoproteins, in cytoplasm (oligo- means “few”) Polysaccharides: starch, glycogen, cellulose, agar, chitin, xanthan gum
A nucleotide: a monomer of DNA http://www.emc.maricopa.edu/faculty/farabee/BIOBK/nucleotide.gif
Nucleic acids are the polymers made from nucleotides. DNA tRNA http://www.biochem.uwo.ca/meds/medna/IMG/tRNA.GIF
Structure of DNA http://academic.brooklyn.cuny.edu/biology/bio4fv/page/molecular%20biology/16-05-doublehelix.jpg
Phospholipids are essential building blocks for membranes; sterol-type molecules are rarely found in bacteria.
A lipid polymer: a biodegradable plastic made by bacteria. Ester bond Polyesters
Peptide bond covalent bond that connects two amino acids.
Levels of protein structure Primary: amino acids and the order they are in; determined from the DNA. Secondary: alpha helix and beta pleated sheet; twisting of chain in space. Tertiary: 3D shape of protein. Quaternary: more than 1 polypeptide combining to form a functional unit. http://www.contexo.info/DNA_Basics/images/proteinstructuresweb.gif
Role of these molecules in cell structure • Polysaccharides • Present in protective layers around the cell • Part of cell wall • Nucleic acids • Blueprint of cell, location of genes • Ribosomes contain RNA • Lipids • Major component of cell membranes, barrier • Proteins • Enzymes, carry out chemical reactions • Structural components
Don’t forget the water • ALL living things require water • Water is major component of cytoplasm • All small molecules are dissolved in water • All large molecules have water attached to them • Cells modify their chemistry to retain water • You die of dehydration before you starve • Every polymer, every structure in the cell is surrounded by water. http://media.nasaexplores.com/lessons/04-070/images/faucet.jpg
Review • Microbes include • Bacteria, which are prokaryotic cells • Fungi and protozoa, which are eukaryotic cells • Viruses, which are not cellular so maybe not alive • All of these are comprised of 4 types of molecules • There’s small and large example of all 4 types • So Why do we study microbes? www.pasteur.fr/.../im/micros/pasteur%20copie.jpg
Why Study Microbes? • Major impact on health • Responsible for disease in humans, animals, plants • Major impact on environment • Major decomposers • Nutrient cycling, elemental cycling • Microbes are talented • Live under extreme conditions • Protect against disease • Eat oil, toxic waste (bioremediation) • Make plastic • Spoil food, make food • Use light, produce light