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The cytoskeleton is a meshwork of protein filaments that provides support and movementCytoskeletal proteins (Actin, myosin, tubulin and others) are responsible for cell movement and cell shapeMuscle cells are special cells with exceptional cytoskeleton that allows for contraction°Cell junctions (connections)Specializations of the cell membrane that attach neighboring cells and allow materials to move between themThe cell is a complex and confusing place. And the ultimate explanation for itmust be chemical and molecularFebruary 20, 2015The chemistry of life is the chemistry of carbonCarbon’s almost unlimited ability to bond to itself makes it possible to form macromolecules of great length and complexity°Carbon chemistry can be understood in terms of functional groups:Amino, carbonyl, carboxyl, hydroxyl, phosphate, sulfhydrylCarboxyl groups are acids: H+ ion donor = organic acidsoCarbon double bonded to oxygen and single bond to OHAmino: H+ ion acceptor = organic base°The presence of similar chemical groups in two molecules tells us that they will have some properties in common (Example: amino and carboxyl groups in both of these molecules)°Living things are based on “macromolecules”:No precise definition (MW > 1,000 d)
Usually assembled from simpler subunits by the process of polymerization:oMonomer, dimer, trimer, tetramer, polymerIf all the same, the polymer is a homopolymerIf all different, the polymer is a heteropolymer°Four major classes of biological macromolecules:°LipidsBasis: hydrocarbon chain – made up of hydrogen and carbonConstructed from fatty acidsTriglyceride (a lipid) – cooking oilsFats (lipids) are macromolecules that are waxy or oily and soluble in organic solvents (such as ethanol, acetone, benzene)Many lipids have water-loving and water-hating portionsoHave polar heads (hydrophilic)oNonpolar tails (hydrophobic)Making them particularly good at forming membranes phospholipid bilayer, or membraneStearic acid – a saturatedfatty acid (maximum number of hydrogens for each carbon)Oleic acid – unsaturatedacid (in the middle there is a double bondtherefore we cannot have the maximum # of hydrogens)Linolenic acid – poly-unsaturated(tells us how many double bonds there are)°Carbohydrates (sugars polysaccharides)Have the general formula: (CH2O)nwhere n>3oGlucose C6H12O6oWhen the linear form closes to form a ring, the position of the – OH group on carbon #1 determines if it will close in the α (alpha) or β (beta) formGlucose is a monosaccharide (simple sugar)… which can be joined to other sugars to form disaccharides – or polysaccharidesStarch – a polymer of glucoseoTens of thousands of glucoses linked together
oStarch and cellulose are both polymers of glucose. Monomers of starch are linked by α (alpha)-1,4 glycosidic bondsoCellulose uses β (beta)-1,4 glycosidic bonds – oxygen is in βWe do not have enzyme to break down β bond°Nucleic acids (nucleotides nucleic acids)Nucleic acids are polymers of nucleotides