BIO LECTURE 1710 CH3
BIO LECTURE 1710 CH3 BIOL 1710
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This 6 page Class Notes was uploaded by Anoosha Mardani on Tuesday September 20, 2016. The Class Notes belongs to BIOL 1710 at University of North Texas taught by Mark Burleson in Fall 2016. Since its upload, it has received 5 views. For similar materials see BIOL SCI MAJORS 1 in Biochemistry at University of North Texas.
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Date Created: 09/20/16
Bio Lecture Sept 12 2016 Chapter 3 Notes: Biological Macromolecules Living things are made up of four classes of large biological molecules: 1. carbohydrates 2. lipids 3. proteins 4. nucleic acids • small organic molecules (subunits) are joined together to form larger molecules • MACROMOLECULES- large molecules composed of thousands of covalently connected atoms Macromolecules are polymers, built from monomers • A polymer is a long molecule consisting of many similar building blocks • The small building-block molecules are called monomers • Three of the four classes of life’s organic molecules are polymers: – Carbohydrates – Proteins – Nucleic acids The Synthesis and Breakdown of Polymers • A dehydration reaction (synthesis) occurs when two monomers bond together through the loss of a water molecule • Enzymes speed up the dehydration process • Polymers are disassembled to monomers by hydrolysis, a reaction that is essentially the reverse of the dehydration reaction Carbohydrates serve as fuel and building material • Carbohydrates - sugars and polymers of sugars • simplest carbohydrates are monosaccharides, or single sugars • Carbohydrate macromolecules are polysaccharides, polymers composed of many sugar building blocks • Recognition molecules – glycolipids, glycoprotein Sugars • Monosaccharides have molecular formulas that are usually multiples of CH O 2 • Glucose (C H 6 )12s 6he most common monosaccharide • Though often drawn as linear skeletons, in aqueous solutions many sugars form rings • Monosaccharides serve as a major fuel for cells and as raw material for building molecules • disaccharides are formed when a dehydration reaction joins two monosaccharides • This covalent bond is called a glycosidic linkage Polysaccharides • Polysaccharides, the polymers of sugars, have storage and structural roles • The structure and function of a polysaccharide are determined by its sugar monomers and the positions of glycosidic linkages Storage Polysaccharides • Starch - storage polysaccharide of plants, consists entirely of glucose monomers • Plants store surplus starch as granules within chloroplasts and other plastids • Glycogen is a storage polysaccharide in animals • Humans and other vertebrates store glycogen mainly in liver and muscle cells Structural Polysaccharides • cellulose is a major component of the tough wall of plant cells • Like starch, cellulose is a polymer of glucose, but the glycosidic linkages differ • The difference is based on two ring forms for glucose: alpha (α) and beta (β) • Enzymes that digest starch by hydrolyzing α linkages can’t hydrolyze β linkages in cellulose • Many herbivores have symbiotic relationships with microbes • Chitin - structural polysaccharide in the exoskeleton of arthropods • cell walls of fungi Lipids: a diverse group of hydrophobic molecules • class of large biological molecules that do not form polymers • The unifying feature of lipids is having little or no affinity for water – non polar • The most biologically important lipids are fats, phospholipids, steroids and waxes Biological Functions of Lipids • source of stored metabolic energy • structural matrices and permeability barriers in biological membranes. • special lipids act as both intracellular messengers and extracellular messengers such as hormones • insulation and shock absorber Fats - constructed from two types of smaller molecules: glycerol and fatty acids 1. Glycerol - three-carbon alcohol with a hydroxyl group attached to each carbon 2. Fatty acid consists of a carboxyl group attached to a long carbon skeleton • Fatty acids vary in length (number of carbons) and in the number and locations of double bonds • Saturated fatty acids have the maximum number of hydrogen atoms possible and no double bonds – animal fats • Unsaturated fatty acids have one or more double bonds – plant fats – polyunsaturated = many double bonds • diets rich in saturated fats contribute to cardiovascular disease • Hydrogenation - process of converting unsaturated fats to saturated fats by adding hydrogen • Hydrogenating vegetable oils creates unsaturated fats with trans double bonds • trans fats may contribute more than saturated fats to cardiovascular disease Phospholipids - two fatty acids and a phosphate group attached to glycerol Steroids Steroids - lipids characterized by a carbon skeleton consisting of four fused rings • • Cholesterol is a component in animal cell membranes Proteins • more than 50% of the dry mass of cells 1. structure 2. storage 3. transport 4. cellular communications 5. movement 6. defense Polypeptides Polypeptides are polymers built from the same set of 20 amino acids • • A protein consists of one or more polypeptides • Primary structure, the sequence of amino acids in a protein • determined by inherited genetic information • secondary structure results from hydrogen bonds between repeating constituents of the polypeptide backbone • α helix – coil • β pleated sheet – folded structure • Tertiary structure determined by interactions between R groups • include hydrogen bonds, ionic bonds, hydrophobic interactions, and van der Waals interactions • disulfide bridges (strong covalent bonds) reinforce the protein structure • Quaternary structure - when two or more polypeptide chains form one macromolecule • Collagen - fibrous protein consisting of three polypeptides coiled like a rope • Hemoglobin - globular protein consisting of four polypeptides: two alpha and two beta chains • physical and chemical conditions affect structure • Alterations in pH, salt concentration, temperature, or other environmental factors cause protein denaturation • A denatured protein is biologically inactive Which molecule below can form a dimer (two of the molecules) linked by a covalent bond? An example of a hydrogen bond is the bond between A. C and H in methane (CH ). 4 B. the H of one water molecule and the O of another water molecule. + - C. Na and Cl in salt. D. the two hydrogen atoms in a molecule of hydrogen gas (H ). + - 2 E. Mg and Cl in MgCl . 2
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