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Properties of Water Sara Burnham Biology HHS Types of Bonds • Ionic bond – one or more electrons transferred from one atom to another • Covalent bond – shared electrons; single, double, or triple bond • Van der Waals – slight attraction between oppositely charged regions of nearby molecules Water is Polar • Shared electrons stay closer to oxygen than hydrogen because oxygen has a stronger attraction for electrons • Oxygen on one end and hydrogen on the other end • Since electrons spend more time near oxygen atom, oxygen has a slight – charge and hydrogen has a slight + charge • Water is polar because electrons and charge are unevenly distributed. Hydrogen Bonding • Hydrogen bonding occurs between neighboring water molecules because of the slight charge • Hydrogen atom of one water molecule is attracted to the oxygen atom of a neighboring molecule • Creates surface tension Surface Tension • Water strider can “walk on water” because of surface tension • Cohesion creates surface tension • Cohesion is the the attraction of between molecules of the same substance. Solution • Mixture where water is the solvent and the substance dissolved is the solute • Ex: sugar in water, salt in water Suspension • Mixture where material does not dissolve in water • Ex: flour in water, mud in water Carbon • Important building block of life • Base of every organic molecule • 4 valence electrons – Each has the ability to join with an electron from another atom forming a strong covalent bond – Can bond to other carbon atoms forming chains almost unlimited in length; single, double, or even triple bonds can be formed Carbohydrates • Made up on carbon, hydrogen, and oxygen • Body’s main source of energy • Can also be used for structural purpose • Sugars Monosaccharides • Single sugars • Ex: glucose, galactose, fructose Disaccharides • Two monosaccharides bound together • Ex: lactose (glucose and galactose), sucrose (glucose and fructose), and maltose (two glucose molecules) Polysaccharide • Thousands of monosaccharides linked together • Ex: glycogen, starch cellulose Lipids • • • • • Made mostly of carbon and hydrogen Not soluble in water Consists of fats, oils, and waxes Can be used to store energy Many lipids are formed with glycerol and a fatty acid tail • Steroids are lipids Saturated • • • • Lipid with only single bonds “Saturated with hydrogens” Solid at room temperature Ex: animal fat (lard), fatty meats Unsaturated • Has at least one double bond • Liquid at room temperature • Ex: vegetable oil, olive oil, canola oil Polyunsaturated • Many double bonds (more than one can be considered polyunsaturated) Nucleic Acids • Nucleotides joined covalently • Contain carbon, hydrogen, oxygen, nitrogen, and phosphorous • Polymers from monomers called nucleotides • Nucleotide has 5-carbon sugar, phosphate group, and a nitrogenous baase • RNA – ribose sugar; DNA – deoxyribose sugar – Store genetic information Proteins • Contain carbon, nitrogen, hydrogen, and oxygen • Monomer of protein (polymer) is amino acid – Have amino group (-NH2) at one end and a carboxyl group (-COOH) at the other end • More than 20 different amino acids found in nature • When two or more amino acids are bound, still has amino group on one end and carboxyl group on the other end • Polypeptide chain has three or more amino acids bound together • Polypeptide bond forms as a condensation reaction (rxn) joins the amino group of one amino acid with the carboxyl group of the next in line H2O released Peptides • Short polymers