How To Make Biological Molecules (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 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 build a polymer Synthesis joins monomers by “taking” H2O out one monomer donates OH– other monomer donates H+ together these form H2O requires energy & enzymes H2O HO H enzyme Dehydration synthesis Condensation reaction

How to break down a polymer Breaking up is hard to do! 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 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

Any Questions?? 2007-2008

OH H HO CH2OH O Carbohydrates energy molecules

Carbohydrates are composed of C, H, O Function: energy energy storage raw materials structural materials Monomer: sugars ex: sugars, starches, cellulose (CH2O)x C6H12O6 carb = carbon hydr = hydrogen ate = oxygen compound sugar

Where do you find solutions in biology? Sugar structure 5C & 6C sugars form rings in solution Where do you find solutions in biology? In cells! Carbons are numbered

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 glucose Disaccharides 2 monomers sucrose Polysaccharides large polymers starch

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

Polymers of glucose units are used as temporary food storage in both plant and animal cells. Glucose units are connected to one another by 1, 4-linkages to make a linear polymer and by 1, 6-linkages to make branch points.

Numbered carbons C 6' C O 5' C C 4' 1' C C 3' 2'

Linear vs. branched polysaccharides starch (plant) What does branching do? 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)

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 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 Gorilla can digest cellulose well; no need to eat other sugars 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

Tell me about the rabbits, again, George! Helpful bacteria How can herbivores digest cellulose so well? BACTERIA live in their digestive systems & help digest cellulose-rich (grass) meals Caprophage I eat WHAT! Tell me about the rabbits, again, George! Ruminants

Review Questions

Which of the following is a polymer? Simple sugar (aka monosaccharide) Carbon atoms Glucose Cellulose deoxyribose

Starch and Glycogen both Serve as energy storage for organisms 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