History 4 Types of Compound Light Microscopy 1665 Robert Hooke was the first to describe microorganisms 1676 Antoni van Leeuwenhoek was the first to describe bacteria Optimize image resolution by using lenses with high light gathering characteristics limit of resolution 0 2 micrometers Brightfield o Simplest o Specimen is illuminated magnified 1000x o Specimen stained to increase contrast o 10x objective 100x total magnification o 100x objective 1000x total magnification Phase Contrast and Darkfield o Visualize live samples o No staining required o Image contrast is derived from cell structures Fluorescent o Visualization of autofluorescent molecules or fluorescent stains o Ex Chlorophyll autofluorescence DAPI fluorescence o Transmission Electron Microscope TEM used for observing internal cell structure o Scanning Electron Microscope SEM used for observing 3D images and cell surfaces Limit of resolution is 0 2 4 nanometers 2 Types of Electron Microscopy Electron Microscopes BIOL 2051 EXAM 1 Structure and Function 1 9 Prokaryotes Significance of Being Small Basic Components of All Cells Microorganisms are as small as 0 2 micrometers o Mycoplasma pneumoniae is the smallest free living bacterium pathogenic Size affects physiology growth rate and ecology High surface volume ratio aids in nutrient and waste exchange with the environment o Smaller cells have higher surface volume ratio Cytoplasm Cytoplasmic membrane Ribosomes Include Domains Bacteria and Archaea Contain o Cytoplasm o Cytoplasmic membrane o Cell wall o Nucleoid o Ribosomes o Plasmid Typically much smaller than eukaryotes Include Domain Eukarya All cells contain o Cytoplasmic membrane o Endoplasmic reticulum o Ribosomes o Nucleus o Nuclear membrane o Golgi complex o Cytoplasm Some cells contain o Mitrochondrion or Hydrogenosome o Chloroplast o Lysosome Typically much bigger than prokaryotes Fluid highly selective permeable barrier Made of lipids and proteins Phospholipids form a lipid bilayer with a Hydrophobic polar exterior and a Hydrophilic non polar interior o In Eukarya and Bacteria fatty acids are linked to glycerol by ester linkages Integral membrane proteins span this membrane Other lipids in cytoplasmic membrane Cytoplasmic Membrane Eukaryotes BIOL 2051 EXAM 1 Structure and Function 2 9 Nucleus Endoplasmic Reticulum ER o Sterols in Eukarya o Hopanoids in Bacteria In Archaea o There is a lipid monolayer o More resistant to peeling apart than bilayers o Linked by ether linkages o Contain biphytanyl Functions 1 Permeability Barrier prevents leakage and functions as a gateway for transport of nutrients into and out of the cell 2 Protein Anchor site of many proteins involve in transport bioenergetics and chemotaxis 3 Energy Conservation site of generation and use of the proton motive force Contains DNA Has pores join the outer and inner membrane to allow for import and export of proteins and nucleic acids Contains nucleolus where rRNA is made Rough ER continuous with nuclear outer membrane o Contains ribosomes o Site of protein synthesis o Makes glycoprotein s and new membrane material Smooth ER continuous with the rough ER o Lipid synthesis o Carbohydrate metabolism Chemically modifies carbohydrates on ER glycoprotein s Sorts molecules from the ER o Secreted from the cell o Used within the cell Produced by budding of the Golgi Complex pH 5 Contains digestive enzymes lipases nucleases proteases etc Function Site of oxidation oxidase enzymes break down lipids and other molecules for energy o Recycle macromolecules o Kill foreign bacteria o Apoptosis cell suicide o Beta oxidation of lipids breaks down a 2 carbon acetyl unit at a time o Acetyl CoA is then transported into the cytosol Golgi Complex Lysosome Peroxisome BIOL 2051 EXAM 1 Structure and Function 3 9 Contains o Catalase to degrade H2O2 o Superoxide dismutase to degrade O2 Mitochondrion Outer Membrane o Rigid o Somewhat permeable ions small organic molecules Inner Membrane Cristae folds o Less rigid and folded o Less permeable transport through specific proteins o Sites of electron transport and ATP production Matrix o Aqueous inside of the mitochondrion o Contains enzymes of the Citric Acid Cycle Hydrogenosome Instead of the Mitochondrion in some anaerobic eukaryotes Site of ATP production but no electron transport No Citric Acid Cycle Chloroplast Found in phototrophic eukaryotes Surrounded by a double membrane Stroma aqueous inside of the chloroplast o Site of Calvin Benson Cycle RuBisCO fixes CO2 into organic compounds Grana of Thylakoid Membranes o Stacks of flattened membrane discs o Contain light harvesting pigments such as chlorophyll o Site of photosynthetic electron transport and ATP production Cytoskeleton Skeleton of the cell Microfilaments polymers of actin o Define maintain change cell shape BIOL 2051 EXAM 1 Structure and Function 4 9 o Cell motility cytoplasmic streaming Microtubules polymers of tubulin o Maintain cell shape o Cell motility form flagella and cilia o Movement of organelles and chromosomes PROKARYOTIC Cytoskeleton o FtsZ Protein structure similar to tubulin Determines where cell division will occur o FtsA and MreB Protein structures similar to actin FtsA proteins help hold FtsZ proteins in place MreB proteins determine where new cell wall will be inserted into an expanding dividing cell Cocci shaped bacteria lack MreB gene Cell Wall Structure o Proteins o Glycoprotein s o Polysaccharides o Some lack cell walls Functions o Protection o Maintain cell shape o Prevents osmotic lysis o Interacts with the environment Eukarya cell walls o Cellulose ex algae o Chitin ex fungi o Glycoprotein widespread ex fungi slime molds yeast Bacteria cell walls o Mycoplasma and Chlamydia groups lack a cell wall o Planctomyces group has protein cell walls o Peptidoglycan is found in all other groups o Gram Negative Bacteria have only a few layers of peptidoglycan only 10 of cell wall is peptidoglycan contains an outer membrane o Gram Positive Bacteria have several layers of peptidoglycan as much as 90 of the cell wall is peptidoglycan BIOL 2051 EXAM 1 Structure and Function 5 9 o Repeating subunit forms the peptidoglycan layer 2 sugars repeating N Acetylglucosamine and N Acetylmuramic acid 4 amino acid tetrapeptide crosslink o Teichoic Acids negatively charged polymers containing glycerophosphate or ribitol residues Bind Ca2 and Mg2 o Lipoteichoic Acids Teichoic acids covalently linked to membrane lipids span the membrane o Lipopolysaccharides contain