Macromolecules (Carbs and Lipids)

Biology.. Lec1: Macromolcules (Carbs and lipids) • All living things are made up of large biological molecules.. large biological molecules.. Carbohydrate lipids proteins Nuclic acids • Macromolecules are polymers which means (large molecules) composed of thousands of covalently connected (monomers). • A polymer is a long molecule consisting of Many repeated monomers. • Three of the four classes of life’s large organic molecules are polymers: - Carbohydrates/ polysaccharides from monosaccharide - Proteins from amino acids - Nucleic acids from nucleotide • Note: Lipids are not polymers • A condensation or dehydration reaction occurs when two monomers bond together through the loss of a water molecule. • Polymers are disassembled to monomers by hydrolysis, the reverse of the dehydration reaction. Carbohydrate • Carbohydrates serve as fuel ( source of energy) and building material (for plants and fungus). • Carbohydrates include sugars and polymers of sugars. • The simplest carbohydrates are monosaccharides, or single sugars. • Carbohydrate macromolecules are polysaccharides, polymers composed of many sugar building blocks. • Monosaccharides have molecular formulas that are usually multiples of CH2O.. ( from 3 to 6) • Glucose (C6H12O6) is the most common monosaccharide.. • Monosaccharides are classified by: – The location of the carbonyl group (as aldose C1 or Ketose C2). – The number of carbons in the carbon skeleton (3C to 6C). • Monosaccharides serve as a major fuel for cells and as raw material for building molecules. • A disaccharide is formed when a dehydration reaction joins only two monosaccharides. • This covalent bond is called a glycosidic linkage / bond. • Glycosidic bond, a linkage which joins carbs together or between carbs monomers • Lactose intolerance: • Digestive system cannot digest milk sugar (lactose). • The symptoms of this case: vomiting, stomach ache, nausea, diarrhea after drinking milk or eating dairy product. • It may lead to deficiency in vitamin D. • Solution: taking Vitamin from different sources or drinking free lactose milk. • Polysaccharides: 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. • Starch, a 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 (in liver and muscle cells). • The polysaccharide 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 and beta. • Polymers with  glucose are helical. • Polymers with  glucose are straight. • In straight structures, H atoms on one strand can bond with OH groups on other strands. • Parallel cellulose molecules held together this way are grouped into microfibrils, which form strong building materials for plants. • Enzymes that digest starch by hydrolyzing  linkages can’t hydrolyze  linkages in cellulose. • Cellulose in human food passes through the digestive tract as insoluble fiber. • Some microbes use enzymes to digest cellulose. • Many herbivores, from cows to termites, have symbiotic relationships with these microbes. Lipids • Lipids are a diverse group of hydrophobic molecules. • Lipids are the one class do not form polymers (not a real Macromolecule). • Lipids are hydrophobic because they consist mostly of hydrocarbons, which form nonpolar covalent bonds. • The most biologically important lipids are: 1- Fats 2- Phospholipids 3- Steroids • Fats are constructed from two types of smaller molecules: 1- glycerol 2- fatty acids • Glycerol is a three-carbon alcohol with a hydroxyl group attached to each carbon. • A fatty acid consists of a carboxyl group attached to a long carbon skeleton. • In a fat, three fatty acids are joined to glycerol by an ester linkage, creating a triacylglycerol, or triglyceride. • 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. • Unsaturated fatty acids have one or more double bonds. • Fats made from saturated fatty acids are called saturated fats, and are solid at room temperature such as most animal fats. • Fats made from unsaturated fatty acids are called unsaturated fats or oils, and are liquid at room temperature like plant fats and fish fats. • A diet rich in saturated fats may contribute to cardiovascular disease through plaque deposits. • Hydrogenation is the process of converting unsaturated fats to saturated fats by adding hydrogen. • Hydrogenating vegetable oils also creates unsaturated fats with trans double bonds. • These trans fats may contribute more than saturated fats to cardiovascular disease. • The major function of fats is energy storage • Humans and other mammals store their long term food reserves in adipose cells • Adipose tissue also cushions vital organs and insulates the body • In a phospholipid, two fatty acids and a phosphate group are attached to glycerol • The two fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head. • When phospholipids are added to water, they self-assemble into a bilayer, with the hydrophobic tails pointing toward the interior. • The structure of phospholipids results in a bilayer arrangement found in cell membranes. • Phospholipids are the major component of all cell membranes • Steroids are lipids characterized by a carbon skeleton consisting of four fused rings. • Cholesterol, a type of steroid, is a component in animal cell membranes and a precursor from which other steroids are synthesized. • A high level of cholesterol in the blood may contribute to cardiovascular disease. 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