2 Macromolecules Large organic molecules built by smaller molecules. 4 major classes of macromolecules:carbohydrateslipidsproteinsnucleic acids
3 Dehydration synthesis Polymers:Long molecules built by linking repeating building blocks in a chainMonomers are small building blockscovalent bonds betweenH2OHOH• great variety of polymers can be built from a small set of monomers• monomers can be connected in many combinations like the 26 letters in the alphabet can be used to create a great diversity of words• each cell has millions of different macromoleculesDehydration synthesis
4 To build a polymer Take out water: called dehydration synthesis or condensation reaction:joins monomers by “taking” H2O outone monomer loses OH–other monomer loses H+requires energy & enzymesH2OHOHenzymeDehydration synthesisCondensation reaction
5 To break down a polymer Add H2O to breakdown polymers requires enzymes reverse of dehydration synthesisH2O is split into H+ and OH–H+ & OH– attach to endsrequires enzymesreleases energyH2OHOHenzymeMost macromolecules are polymers• build:condensation (dehydration) reaction• breakdown:hydrolysisAn immense variety of polymers can be built from a small set of monomersHydrolysisDigestion
14 Polysaccharides Polymers of sugars Function: energy storage structure starch (plants)glycogen (animals)Glucose stored in liverstructurecellulose (plants)chitin (arthropods & fungi)Polysaccharides are polymers of hundreds to thousands of monosaccharides
15 Chitin: polysaccharide in lobster shells, insect bodies CH2OHOHOHHOHHOHHHNHCOCH3(b) Chitin forms the exo- skeleton of arthropods. This cicada is molting, shedding its old exoskeleton and emergingin adult form. It is also found in Fungal Cell Walls.(a) The structure of thechitin monomer.(c) Chitin is used to make astrong and flexible surgicalthread that decomposes afterthe wound or incision heals.
16 Linear vs. branched polysaccharides slow releasestarch(plant)energy storageCan you see the difference between starch & glycogen?Which is easier to digest?Glycogen = many branches = many endsEnzyme can digest at multiple ends. Animals use glycogen for energy storage == want rapid release.Form follows function.APBio/TOPICS/Biochemistry/MoviesAP/05_07Polysaccharides_A.swfglycogen(animal)fast release
17 Polysaccharides Molecular structure determines function in starch in celluloseisomers of glucosestructure determines function…
18 Cellulose Most abundant organic compound on Earth herbivores have evolved a mechanism to digest cellulosemost carnivores have notthat’s why they eat meat to get their energy & nutrientscellulose = undigestible roughageCross-linking between polysaccharide chains:= rigid & hard to digestThe digestion of cellulose governs the life strategy of herbivores.Either you do it really well and you’re a cow or an elephant (spend a long time digesting a lot of food with a little help from some microbes & have to walk around slowly for a long time carrying a lot of food in your stomach)Or you do it inefficiently and have to supplement your diet with simple sugars, like fruit and nectar, and you’re a gorilla.
19 Digesting starch vs. cellulose enzymestarch easy to digestcellulose hard to digestStarch = all the glycosidic linkage are on same side = molecule lies flatCellulose = cross linking between OH (H bonds) = rigid structureenzyme
20 BACTERIA such as E. coli live in digestive systems & help digest cellulose-rich grass.