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Chapter 5: Macromolecules

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1 Chapter 5: Macromolecules

2 Macromolecules Large organic molecules built by smaller molecules.
4 major classes of macromolecules: carbohydrates lipids proteins nucleic acids

3 Dehydration synthesis
Polymers: Long molecules built by linking repeating building blocks in a chain Monomers are small building blocks covalent bonds between H2O HO H • 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 macromolecules Dehydration synthesis

4 To build a polymer Take out water: called dehydration synthesis
or condensation reaction: joins monomers by “taking” H2O out one monomer loses OH– other monomer loses H+ requires energy & enzymes H2O HO H enzyme Dehydration synthesis Condensation reaction

5 To break down a polymer Add H2O to breakdown polymers requires enzymes
reverse of dehydration synthesis H2O is split into H+ and OH– H+ & OH– attach to ends requires enzymes releases energy H2O HO H enzyme Most macromolecules are polymers • build: condensation (dehydration) reaction • breakdown: hydrolysis An immense variety of polymers can be built from a small set of monomers Hydrolysis Digestion

6 Carbohydrates

7 Carbohydrates - composed of C, H, O Carb-o – hydrate Used for: energy
energy storage raw materials structural materials Building blocks are sugars carb = carbon hydr = hydrogen ate = oxygen compound sugar

8 Sugar structure 5C & 6C sugars form rings in solution
Carbons are numbered

9 Carbons are numbered: C 6' C O 5' C C 4' 1' C C 3' 2'

10 Sugars: end in -ose Monosaccharides: glucose fructose
Disaccharides: glucose + fructose = sucrose Others: maltose, lactose, dextrose

11 Simple & complex sugars
Monosaccharides 1 monomer glucose Disaccharides 2 monomers sucrose Polysaccharides large polymers starch

12 Building sugars Dehydration synthesis monosaccharides disaccharide |
H2O maltose | glucose | glucose | maltose glycosidic linkage

13 Building sugars Dehydration synthesis monosaccharides disaccharide |
H2O | glucose | fructose | sucrose (table sugar) sucrose = table sugar

14 Polysaccharides Polymers of sugars Function: energy storage structure
starch (plants) glycogen (animals) Glucose stored in liver structure cellulose (plants) chitin (arthropods & fungi) Polysaccharides are polymers of hundreds to thousands of monosaccharides

15 Chitin: polysaccharide in lobster shells, insect bodies
CH2OH O H OH H OH H OH H H NH C O CH3 (b) Chitin forms the exo- skeleton of arthropods. This cicada is molting, shedding its old exoskeleton and emerging in adult form. It is also found in Fungal Cell Walls. (a) The structure of the chitin monomer. (c) Chitin is used to make a strong and flexible surgical thread that decomposes after the wound or incision heals.

16 Linear vs. branched polysaccharides
slow release starch (plant) energy storage Can you see the difference between starch & glycogen? Which is easier to digest? Glycogen = many branches = many ends Enzyme can digest at multiple ends. Animals use glycogen for energy storage == want rapid release. Form follows function. APBio/TOPICS/Biochemistry/MoviesAP/05_07Polysaccharides_A.swf glycogen (animal) fast release

17 Polysaccharides Molecular structure determines function in starch
in cellulose isomers of glucose structure determines function…

18 Cellulose Most abundant organic compound on Earth
herbivores have evolved a mechanism to digest cellulose most carnivores have not that’s why they eat meat to get their energy & nutrients cellulose = undigestible roughage Cross-linking between polysaccharide chains: = rigid & hard to digest The 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
enzyme starch easy to digest cellulose hard to digest Starch = all the glycosidic linkage are on same side = molecule lies flat Cellulose = cross linking between OH (H bonds) = rigid structure enzyme

20 BACTERIA such as E. coli live in digestive systems & help digest cellulose-rich grass.

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