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Chapter 2 - The Cell - Structure and Function2.1 BiomoleculesBiomoleculesCarbon has four electrons in its outer shell and forms covalent bonds by sharing these electrons with other atoms, including other carbon atomsoOther atoms common to biomolecules include oxygen, hydrogen, and nitrogen oAbility of carbon to share four electrons and to form covalent bonds with other carbon atoms enables carbon-containing molecules to be large and complexFour basic types of biomolecules are carbohydrates, lipids, proteins, and nucleotidesCarbohydratesCarbohydrates are composed of carbon, hydrogen, and oxygen in a ratio of 1:2:1, with the general chemical formula (CH2O)n.The carbons actually bond to hydroxyl groups (-OH) and hydrogens (-H)oPresence of several hydroxyl groups makes carbohydrates polar molecules so they readily dissolve in waterMonosaccharides, Disaccharides, and PolysaccharidesCarbohydrates can be classified further into 3 major groups: Monosaccharides, Disaccharides, and PolysaccharidesMonosaccharides are simple sugars composed of a single unitoMost common is glucose, an important source of energy for our cellsoGeneral formula is C6H12O6oTwo other common: Fructose and galactose Share the same general formula as glucoseAtoms are arranged differently, given each its own chemical propertiesoRibose and deoxyribose – important component of nucleotidesDisaccharides are carbohydrates formed by the covalent bonding of two monosaccharidesoCommon examples: Sucrose: composed of a glucose subunit and a fructose subunit joined togetherTable sugarLactose: composed of a glucose subunit and a galactose subunit joined togetherCarbohydrate found in milkPolysaccharides are carbohydrates formed by the covalent bonding of several monosaccharidesGlycogen is a polymer of glucose subunitsoFound in animal cells
oSeveral types of cells in the body can store glucose as glycogen and later break it down when they need glucose for energyoGlycogen is needed for that reason: if cells store energy in the form of monosaccharides, they would exert an osmotic force that would draw water into the cells, making them swell and possibly burstStarch is a polysaccharide found in plantsoHumans consume starch in various plant food productsThe digestion process makes the glucose subunits of starch available as energy sourcesCellulose is another polysaccharide found in plants and consumed by humans but we’re unable to digest and absorb itoKnown as dietary fiberPasses through our GI tractSynthesis and Breakdown of SaccharidesTo synthesize disaccharides and polysaccharides, monosaccharides must be linked together by covalent bonds.