Macromolecules Introduction to Biochemistry PDF

Macromolecules  Introduction Cells join smaller organic molecules together to form larger molecules, called macromolecules The four major classes of macromolecules are: carbohydrates, lipids, proteins, and nucleic acids.  Most macromolecules are polymers Three of t...

Macromolecules  Introduction Cells join smaller organic molecules together to form larger molecules, called macromolecules The four major classes of macromolecules are: carbohydrates, lipids, proteins, and nucleic acids.  Most macromolecules are polymers Three of the four classes of macromolecules form chainlike molecules called polymers. – Polymers consist of many similar or identical building blocks linked by covalent bonds. The repeated units are small molecules called monomers. – Some monomers have other functions of their own. Dehydration synthesis or Condensation reactions make polymers. Removes a water molecule and forms a covalent bond between monomers One monomer provides a hydroxyl group and the other provides a hydrogen and together these form water. This process requires energy and is aided by enzymes. Hydrolysis (opposite of dehydration synthesis) – the covalent bond is broken between monomers in the polymer – a hydrogen atom and hydroxyl group from a split water molecule attaches where the covalent bond used to be. This process releases energy and is aided by enzymes  Carbohydrates -Introduction Carbohydrates include both sugars and polymers. The simplest carbohydrates are monosaccharides or simple sugars. Disaccharides or double sugars, consist of two monosaccharides joined by a condensation reaction. Polysaccharides are polymers of monosaccharides. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Look at the next slide and brainstorm how carbohydrates are similar and how they differ  Fig. 5.3 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Monosaccharides--Characteristics an immediate source of fuel molecular formulas that are multiples of CH2O. Most names for sugars end in –”ose”. classified by the number of carbons and the location of the carbonyl group Isomers—same molecular formula but different structural arrangements Monosaccharides—Functional Groups carbonyl group hydroxyl groups Examples: –glucose, fructose, galactose are all isomers C6H12O6 –glucose--aldose—carbonyl at the end –fructose--ketose—carbonyl in the middle  Monosaccharides are also classified by the number of carbons in the backbone. – Glucose and other six carbon sugars are hexoses. – Five carbon backbones are pentoses and three carbon sugars are trioses. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Drawn as a linear skeleton when in the solid form, monosaccharides form rings in aqueous solution Disaccharides--Characteristics Formed from two monosaccharides joined by a glycosidic linkage Glycosidic linkage Which 2 is an example of functional groups which functional is an ether group? ether formed from? 2 hydroxyls Examples of Disacharides – Sucrose, table sugar, is formed by joining glucose and fructose and is the major transport form of sugars in plants. glucose + fructose ---🡪 sucrose + water Examples: maltose (glucose - glucose) lactose (glucose - galactose) Sucrose (glucose – fructose) Polysaccharides (Storage)--Characteristics polymers of hundreds to thousands of monosaccharides joined by glycosidic linkages polysaccharides function in energy storage Examples of Storage Polysaccharides: 1) Starch -- composed entirely of glucose monomers with 1-4 linkages – Amylose—an unbranched form; forms a helix. – Amylopectin—branched form; more complex. Fig. 5.6a Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings 2) Glycogen Animal storage molecule – highly branched, like amylopectin. – Humans and other vertebrates store glycogen in the liver and muscles but only have about a one day supply. Insert Fig. 5.6b - glycogen Fig. 5.6b Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Functional Groups One key difference among polysaccharides develops from 2 possible ring structures of glucose. – These two ring forms differ in whether the hydroxyl group attached to the number 1 carbon is fixed above (beta glucose) or below (alpha glucose) the ring plane. – Both forms have a 1-4 linkage Fig. 5.7a Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings  Starch is an example of a polysaccharide of alpha glucose monomers. Fig. 5.7 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings  Examples of Structural Polysaccharides Cellulose is a major component of plant cell walls a polymer of glucose monomers, with beta rings. Fig. 5.7c Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings  Fig. 5.8 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings  Chitin, used in the exoskeletons of arthropods (including insects, spiders, and crustaceans). – Chitin is similar to cellulose, except that it contains a nitrogen on each glucose. – Pure chitin is leathery, but the addition of calcium carbonate hardens the chitin. Chitin also forms the structural support for the cell walls of many fungi. Fig. 5.9 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Characteristics of Structural Polysaccharides Form strong building materials polymers built with alpha glucose form helical structures polymers built with beta glucose form straight structures hydrogen bonds form between strands (H from one and OH on the other strand) – Groups of polymers form strong strands, microfibrils, that are basic building material for plants (and humans).  The enzymes that digest starch cannot hydrolyze the beta linkages in cellulose. – Cellulose in our food passes through the digestive tract and is eliminated in feces as “insoluble fiber.” – As it travels through the digestive tract, it abrades the intestinal walls and stimulates the secretion of mucus. Some microbes can digest cellulose to its glucose monomers through the use of cellulase enzymes. Many eukaryotic herbivores, like cows and termites, have symbiotic relationships with cellulolytic microbes, allowing them access to this rich source of energy. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings HOMEWORK Review this material every day or so. There is so much material in this course, you don't want it to build up.