Cell Composition 70 90 water Organic chemistry key to the construction of cells is inherently linked to the properties of water vs organic compounds Consider 4 groups of monomers a single repeated building block Polysaccharides Lipids Nucleic Acids Proteins Macromolecules Sugars Fatty Acids Nucleotides Amino Acids Cell Construction OK using the building blocks we have described let s make a microbe Flagella Function s Swimming movement Predominant chemical composition Protein Pili Sex pilus Mediates DNA transfer during conjugation Protein Common pili or fimbriae Attachment to surfaces protection against phagotrophic engulfment Protein Capsules includes slime layers and glycocalyx Attachment to surfaces protection against phagocytic engulfment occasionally killing or digestion reserve of nutrients or protection against desiccation Usually polysaccharide occasionally polypeptide Gram positive bacteria Prevents osmotic lysis of cell protoplast and confers rigidity and shape on cells Peptidoglycan murein complexed with teichoic acids Gram negative bacteria Peptidoglycan prevents osmotic lysis and confers rigidity and shape outer membrane is permeability barrier associated LPS and proteins have various functions Peptidoglycan murein surrounded by phospholipid proteinlipopolysaccharide outer membrane Plasma membrane Permeability barrier transport of solutes energy generation location of numerous enzyme systems Phospholipid and protein Ribosomes Sites of translation protein synthesis RNA and protein Inclusions Often reserves of nutrients additional specialized functions Highly variable carbohydrate lipid protein or inorganic Chromosome Genetic material of cell DNA Plasmid Extrachromosomal genetic material DNA Cell wall Prokaryote Structure Cell wall Nuclear material membrane Membrane is critical part of how food and waste are transported Selectively permeable Phospholipid layer Transport proteins Cell Membranes The membrane separates the internal part of the cell from the external that these environments remain separate but under CONTROLLED contact is a key to life Membrane Components Phospholipid bilayer Hopanoids which provide additional structural stability similar to sterols cholesterols which provide rigidity to eukaryote cells Proteins direct transport between outside and inside the cell 40 lipid 60 protein Eubacteria vs Archaebacteria Archaeal cell structure Bacterial cell structure Difference Let s look more closely at the membrane though only 8 nm thick it is the principle difference between these 2 groups of microbes Archaea vs bacteria membranes Principle difference between these two is the membrane In archaea lipids are unique they have ether linkages instead of ester linkages Membrane function SELECTIVELY PERMEABLE Passive diffusion Gases O2 N2 CO2 ethanol H2O freely diffuse through layer Osmosis because solute concentration inside the cell are generally higher 10 mM inside the cell water activity is lower inside H2O comes in increased water results in turgor pressure 75psi Protein mediated transport selective and directional transport across the membrane by uniporters and channel proteins these facilitate diffusion still following a gradient and does not require an energy expenditure from the cell Size and diffusion Membrane function 2 Active transport proteins that function to move solutes against a gradient this requires energy Uniport Symport and Antiport proteins guide directional transport of ions molecules across membrane different versions can be quite selective single substance or class of substances as to what they carry Membrane and metabolism As the membrane is the focus of gradients this is where electron transport reactions occur which serve to power the cell in different ways Many enzymes important to metabolic activity are membrane bound H gradients across the membrane Proton Motive Force PMF is what drives ATP production in the cell pH 1 4 0 14 V 23 KJ mol Figure 5 21 Membrane functions other In addition to directing ion molecule transport and providing the locus for energy production membranes are also involved in Phospholipid protein synthesis for membrane Nucleoid division in replication Base for flagella Waste removal Endospore formation Though very small the membrane is critical to cell function Lysis involves the rupture of this membrane and spells certain death for the organism Cell Wall Cell wall structure is also chemically quite different between bacteria and archaea Almost all microbes have a cell wall mycoplasma bacteria do not Bacteria have peptidoglycan archaea use proteins or pseudomurein The cell wall serves to provide additional rigidity to the cell in order to help withstand the turgor pressure developed through osmosis and define the cell shape as well as being part of the defense mechanisms Cell wall structure Two distinct groups of bacteria with very different cell walls Gram negative has an outer lipid membrane different from the inner or plasma membrane Gram positive lacks the outer membrane but has a thicker peptidogycan layer Peptidoglycan layer This layer is responsible for the rigidity of the cell wall composed of N Acetylglucosamine NAG and Nacetylmuramic NAM acids and a small group of amino acids Glysine chains held together with peptide bonds between amino acids to form a sheet Outer membrane Gram Lipid bilayer 7 nm thick made of phospholipids lipopolysaccharides and proteins LPS lipopolysaccharides can get thick and is generally a part that is specifically toxic aka an endotoxin LPS layers are of potential enviornmental importance as a locus of chelators and electron shuttles Porins are proteins that are basically soluble to ions and molecules making the outer layer effectively more porous than the inner membrane though they can act as a sort of sieve External features Glycocalyx aka capsule tightly bound and adhering to cell wall or slime layer more unorganized and loosely bound helps bacteria adhere to surfaces as well as provides defense against viruses Flagella tail that allows movement by rotating and acting as a propeller Pili thin protein tubes for adhesion colonization and adhering to surfaces Inside the cell Cytoplasm everything inside the membrane Nucleoid Chromosome DNA of the organism it is not contained by a nuclear membrane as eukaryote cell Ribosomes made of ribosomal RNA and protein these are responsible for making proteins Vacuoles or vesicles spaces in the cytoplasm that can store solids or gases Mesosomes