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Most Biomacromolecules are Polymers.... A polymer is a long molecule consisting of many small repeating subunits called monomers. These polymers are built by condensation reactions 3 of the 4 classes of life’s organic molecules are polymers: • Carbohydrates • Proteins • Nucleic acids Biomacromolecules: Features Biomacromolecules Biomacromolecules are very large molecules that play an essential role in the structure and function of cells. Biomacromolecule Sub-units Bond Formed by Condensation Cellular Functions Lipids Lipids are not polymers Fatty Acids & Glycerol Ester linkage Energy storage, phospholipids, signalling molecules Complex carbohydrates Polysaccharides Simple sugar monomers Monosaccharides Glycosidic linkage Energy storage, structral components (eg. cellulose) Nucleic Acids Polynucleotides Nucleotide monomers Phosphodiester linkage Genetic material Proteins Polypeptides Amino Acid monomers Peptide linkage Diverse roles; control and regulation, transport, receptors, structural components Biomacromolecules: Features Carbohydrates Carbohydrates are sugars They have roles for energy storage and structural components They are sometimes added to other biomacromolecules to make the • glycoproteins and • glycolipids for the cell membrane Biomacromolecules: Carbohydrates Monosaccharides The simplest carbohydrates are monosaccharides. Most common is glucose- C6H12O6 Notice the carbon skeleton and many polar OH functional groups. • Monosaccharides are highly soluble in water. Carbohydrates: Monosaccharides Monosaccharides Monosaccharides have a characteristic molecular ratio- nCH2O We classify different monosaccharides according to the • location of their carbonyl group • numbering of carbons in the skeleton Monosaccharides form their familiar ring structures in aqueous solutions. Carbohydrates: Monosaccharides Disaccharides Two monosaccharides can join by condensation to form a disaccharide. The covalent bond between monosaccharides is a glycosidic linkage. This is maltose- a disaccharide of 2 glucose monomers. Carbohydrates: Disaccharides Polysaccharides If more than two monosaccharides join we have a polysaccharide. Repeating subunits means that these polysaccharides are also polymers. Polysaccharides are important for energy storage or structural components. Carbohydrates: Polysaccharides Storage Polysaccharides Starch is a polysaccharide of glucose monomers used by plants for energy storage. Plants can store their surplus starch in chloroplasts or in tubers. Chloroplast Starch Granules Carbohydrates: Storage Polysaccharides Storage Polysaccharides Glycogen is the animal world's answer to starch; another polysaccharide of glucose monomers. Vertebrates store glycogen surplus in the liver and muscle cells. Mitochondria Liver Glycogen Granule Carbohydrates: Storage Polysaccharides Structural Polysaccharides Cellulose is also made of glucose monomers for plant cell walls; • threads of cellulose are held together by hydrogen bonds • providing strength, shape, flexibility and • some protection against the pressures of osmosis (turgor). Chitin is another polysaccharide that; • stiffens the exoskeleton of arthropods and insects • provides support to fungal cell walls. Carbohydrates: Structural Polysaccharides Breaking Down Polysaccharides Polysaccharides are built by condensation reactions and enzymes can break them down by hydrolysis. Not every organism can 'digest' every polysaccharide. • Humans can't digest cellulose- it passes through the digestive tract as fibre. • Many herbivores digest cellulose with some help from bacteria in their gut. Carbohydrates: Hydrolysis Overview: Common Carbohydrates Simple Carbohydrates Glucose Energy Fructose Energy Ribose RNA component Disaccharides Sucrose Transport sugar- vascular plants Common Dietary Components Lactose Milk component Maltose Breakdown product of starch Polysaccharides Starch Storage molecule in plants Insoluble macromolecules Glycogen Storage molecule in animals Cellulose Plant cell wall component Chitin Exoskeleton component Monosaccharides General Formula (CH2O)n Complex Carbohydrates Carbohydrates: Overview
