Chapter 5 Molecules of life Four Classes Carbohydrates Lipids Proteins Nucleic Acids Macromolecules Large molecules composed of thousands of covalently connected molecules Concept 5 1 Macromolecules are polymers built from monomers Polymer Big molecules built through monomers 3 of 4 Classes are polymers Carbohydrates Proteins Nucleic Acid Synthesis and Breakdown of polymers Enzymes Macromolecules that speed up the chemical reaction Dehydration reaction two monomers bond through the loss of water Hydrolysis Reverse of dehydration Diversity of Polymers Each cell has thousands of different macromolecules Macromolecules differ between species and with in a species An immense variety of polymers can be built from a small set of monomers Sugars Concept 5 2 Carbohydrates a k a Fuel Carbohydrates are monosaccharaides of single sugars They are polysaccharides built from monosaccharaides Monosaccharaides have molecular formulas that are multiples of CH2O Glucose C6H12O6 is the most common monosaccharaide Classified by 1 Location of carbonyl Group as a Keytone or Aldehyde 2 Number of Carbons Though often drawn as linear chains in aqueous solutions form rings The oxygen on carbon 5 binds to carbon 1 and forms ring of carbon attached to oxygen Carbon 6 is outside the ring Atoms on the right side of the chain are found on the inferior side Bottom Disaccharide Two monosaccharaides after dehydration reaction Glycoside Linkage Covalent Bond Maltose Glucose Glucose from digestion of starch Lactose Glucose Galacatose Sugar in milk Sucrose Glucose Fructose Table Sugar Polysaccharide Polymers of sugars have store and structural roles Two things determine structure and function Sugar Monomers Positions of glycosidic linkages Storage Polysaccharide Starch Storage polysaccharide of plants consisting of only glucose monomers plastids Plants store excess starch as granules within chloroplasts and other Simplest form of starch is amylose Glycogen Storage of polysaccharides in animals Humans and other vertebrates store glycogen mainly in the liver and muscle cells Structural Polysaccharides Polysaccharide cellulose is a major component of the tough wall of plants Like starch cellulose is a polymer of glucose but the glycosidic linages differ The differences based on two ring forms for glucose Alpha and Beta Alpha OH of carbon 1 points down Beta OH of carbon 1 points up Polymers with alpha glucose are helical Polymers with beta glucose are straight H atoms can bond with oh groups of other chains Parallel cellulose molecules held together this way are grouped intro microfibrils which form strong building materials for plants In straight structures H atoms on one strand can bond with OH groups on other strands beta linkages in cellulose fiber that cannot be digested Enzymes that digest starch by hydrolyzing alpha linkages cant hydrolyze Cellulose in human food passes through the digestive tract as an insoluble Some microbes use enzymes to digest cellulose Many herbivores from cows to termites have symbiotic relationships with these microbes Chitin another structural polysaccharide is found in the exoskeleton of Chitin also provides structural support for the cell walls of many fungi Ex arthropods mushrooms Concept 5 3 Lipids Do not form polymers Hydrophobic Because they are hydrocarbons Non Polar Most biologically important fats are phospholipids and steroids Fats Two types Fatty Acids carbon skeleton Glycerol carbon Fatty acids consist of a carboxyl group attached to a long Simplest of lipids Biological fatty acids contain from 12 24 carbons 3 Carbon alcohol with hydroxyl group attached to each Fats separate from water molecules because water forms hydrogen bonds with each other and excludes the fats Fatty Acids are joined to a glycerol by an ester linkage creating triacylgcerol or triglyceride Dehydration reaction connects them Important energy stores Vary in length solids at room temperature stable and stack Saturated fatty Acid Maximum amount of hydrogen atoms possible and no double bonds temperature like oil through plaque deposits fats Unsaturated fatty acid one or more double bonds liquids at room Diet rich in saturated fats may contribute to cardiovascular disease Hydrogenation is the process of concerting unsaturated fats to saturated Trans Fats contribute to cardiovascular disease more than saturated fats hydrogening vegetable oils also creates unsaturated fats with trans double bonds Trans configuration Certain unsaturated fats are not synthesized in human body Not naturally produced must be supplied in the diet Essential fatty acids include the omega 3 fatty acids required for normal growth protect against cardio vascular disease Major function of fats is energy storage 1g of fat stores more than twice as much energy as a gram of a polysaccharide such as starch Humans and animals store fat in adipose cells Adipose tissue also cushions vital organs and insulates the body Phospholipids 2 fatty acids and a phosphate group are attached to a glycerol Hydrophilic head because the phosphate group is hydrophilic and polar When added to water they self assemble into a bilayer with phobic tails point toward the interior Results in a bilayer arrangement found in cell membranes Major component of all a cell membranes Cell can use exocytosis to move things our of the cell through its membrane Steroids membranes synthesized Lipids characterized by a carbon skeleton consisting of four fused rings Differ by the chemical groups that are attached to the rings Cholesterol an important steroid is a component in animal cell Cholesterol is the precursor from which other steroids are Although it is essential high levels in the blood stream lead to cardio vascular disease Steroids function as hormones Vitamin D is a steroid system and bone formation Concept 5 4 Proteins Synthesized in the skin due to the sun s rays Vitamin D is important for calcium absorption in the digestive Proteins account for more than 50 of the dry mass of most cells Protein functions include structural support storage transport cellular communications movement and defense Structural support Hair feathers Storage Oval bumin in egg white stores amino acids Transport Hemoglobin transports oxygen Cellular communications hormones such as insulin receptor proteins for hormones Movement Actin and myosin in muscles Defense against foreign substances Antibodies Enzymes are a type of protein that acts as a catalyst to speed up chemical reactions that carry
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