Ch. 5 - Macromolecules Smaller organic molecules join together to form larger molecules macromolecules 4 major classes of macromolecules: carbohydrates lipids proteins nucleic acids

Dehydration synthesis Polymers Long molecules built by linking repeating building blocks in a chain (polymerization) monomers building blocks repeated small units covalent bonds 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

How to break down a polymer Digestion use H2O to breakdown polymers reverse of dehydration synthesis cleave off one monomer at a time H2O is split into H+ and OH– H+ & OH– attach to ends requires enzymes 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

OH H HO CH2OH O Carbohydrates energy molecules

Carbohydrates are composed of C, H, O Function: energy energy storage structural materials Monomer: simple sugars= glucose, fructose, galactose (CH2O)x C6H12O6 carb = carbon hydr = hydrogen ate = oxygen compound sugar

energy stored in C-C bonds Numbered carbons C 6' C O 5' C C 4' 1' energy stored in C-C bonds C C 3' 2'

Simple & complex sugars OH H HO CH2OH O Glucose Monosaccharides simple 1 monomer sugars These link to form: Disaccharides 2 monomers sucrose Polysaccharides large chains of monosaccharides Starch, glycogen

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

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

Polysaccharides Polymers of sugars Function: costs little energy to build easily reversible = release energy Function: energy storage starch (plants) glycogen (animals) in liver & muscles structure cellulose (plants) chitin (arthropods & fungi) Polysaccharides are polymers of hundreds to thousands of monosaccharides

Polysaccharide diversity Molecular structure determines function in starch in cellulose isomers of glucose structure determines function…

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

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 Cell walls of plants!! 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.

Chitin, a different structural polysaccharide 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.

Cow can digest cellulose well, with the help of bacteria in gut, no need to eat other sugars Gorilla can’t digest cellulose well; must add another sugar source, like fruit to diet 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. APBioTOPICS/20Biochemistry/MoviesAP/Macromolecule-Lifewire.swf

1. Which of the following is a polymer? Carbon atoms Simple sugar (aka monosaccharide) Glucose Cellulose Deoxyribose 2. Starch and Glycogen both: I. Serve as energy storage for organisms II.Provide structure and support III. Are structural isomers of glucose I only II only I and II only I and III only I, II, and III