Biology 1201 Exam 1 study guide Chemical Bonds Atoms gain and lose or share electrons Result of electrical attractions Bonds are a gradation of sharing The number and type of chemical bonds is determined by valence and electronegativity Attraction only exists when there are oppositely charged particles An ion is a charged atom Strongest bonds when dry One atom completely gains an electron and the other completely loses an electron Any two ions of opposite charge can form an ionic bond respectively Ionic Bonds Covalent Bonds Share electrons Pure nonpolar covalent shared equally No polarity The electrons spend the same amount of Polar Covalent Shared unequally Partial charges Spend more time orbiting one nucleus than time orbiting each nucleus the other Strongest bond in water Electronegativity The attraction of a particular atom for the electrons of a covalent bond The more electronegative an atom is the more strongly it pulls shared electrons toward itself A measure of attraction an atom has for electrons The measure of the tendency of an atom to attract a bonding pair of electrons On the periodic table electronegativity increases from left to right and up and down Electronegativity and Bonds Ionic When the difference between electronegativity is 1 7 or greater Pure Covalent A difference of less than 0 5 Polar Covalent The difference is between 0 5 1 7 Polarity Weak Bonds The polarity of a molecule is determined by the types of bonds within a molecule Ionic bonds will be polar and will go into water Not involved in the making of a substance They re within between molecules Occur between different molecules Type of weak bond Weak attractions between atoms on different molecules or different parts of a large molecule Hydrogen bonds Molecules interact but don t fuse Always involves hydrogen Water Hydrogen partial charge Oxygen partial charge Versatile solvent because water molecules are polar The ability of water molecules to form hydrogen bonds with other water molecules and water s ability to dissolve substances that have charges or partial charges are both caused by the partial charges Molecules and Compounds bounded together in a specific pattern Compound A substance consisting of two or more different atoms in specific proportions Molecule Smallest unit of a compound that retains all properties of that compound Ex a single water molecule Next step down the latter are individual atoms that make up the molecule Isomers Molecules with the same molecular formula but a different arrangement of atoms Glucose Isomers Glucose Galactose Fructose Chains Straight vs branch Cis Isomer Groups are on the same side Trans Isomer Groups are on opposite sides Trans moved these are moved across Enantiomers CO H Exact same except that they re mirror images of one another Forms could differ in activity Molecular Weight The sum of the atomic masses for all of the atoms I the molecule Ex H s atomic mass 1 oxygen s 16 H O 1 x 2 16 18 daltons Gram Molecular Weight The mass of a substance equal to its molecular weight in grams Contains a constant number of molecules Avogadro s number 6 022 x 10 Moles and Molar Concentrations 1 mole The mass of a substance equal to its gram molecular weight 1 mole of water 18 grams Acids Bases pH scale Increase the hydrogen ion concentration of a solution Dissociate to produce hydrogen ions Not only adds hydrogen ions to a solution but also removes hydroxide ions The H ions form water with the OH ions Weak acids reversibly release and accept back hydrogen ions Example Carbonic Acid Reduce the hydrogen ion concentration Dissociate to produce hydroxide ions Basic solutions contain a higher OH concentration than H A measure of the hydrogen ion concentration log H The log tells you that it works on a scale of 10 pH declines as H concentration increases Inversely related A pH value less than 7 denotes an acidic solution the lower the number the more acidic The pH for basic solutions is above 7 A solution with a pH of 7 is a neutral aqueous solution Most biological fluids fall within the range pH of 6 8 Exception human digestive stomach juice Each pH unit represents a tenfold difference in H and OH concentrations Relationship with pOH the sum of the pH and pOH is 14 It s an inverse relationship one goes which is a 2 up the other goes down Concentration in moles liter Functional groups Determined by what s attached to the carbon backbone of organic molecules Causes changes in physical characteristics Know how to draw structures It s a test of how well you know them Important Functional Groups Polar Hydroxyl Carbonyl Nonpolar Sulfhydryl Methyl Carboxyl Amino Phosphate C H Acidic Hydroxyl group Polar OH Carbonyl group C O Carbon is double bonded to Oxygen 2 types Ketone located in the carbon chain Aldehyde located on the end of a chain Carboxyl group HO C O H O C O Acids Amino Acids Carboxyl groups make them into acids They add polarity by releasing hydrogen ions in a solution with a 1 charge Make up organic acids and are found in cells in an ionized form COOH Acts like acid ionizes Amino group H N H Amino Acids H3N H2N Phosphate group Commonly used in cells to transfer one organic molecule to another Acidic O O P OH OH Polar covalent bonds lots of polarity 2 hydroxide groups dissociate leading to the release of hydrogen ions making it Acidic Found in DNA and RNA Has the potential to react with water releasing energy and gives a molecule a charge Sulfhydryl group SH Nonpolar Found in Cyteine Amino Acid 2 of them can form covalent bonds with each other and forms cysteines Methyl group CH3 Nonpolar Fatty acid chains In genes DNA and sex hormones Steroid structure C H Not a functional group but important Fat molecules triglyceride Nonpolar all Carbon and Hydrogen Know how to draw the structures The test is a test of how well you know them Carbohydrates Compounds with the ration of 1 carbon 2 hydrogen 1 oxygen For every carbon molecule there s a water molecule Types include Monosaccharides 1 sugar Disaccharides 2 sugars Polysaccharides many Function in animals metabolic fuel glucose and sucrose chitin exoskeleton of many sugars arthropods and storage starch Sugar molecules that fuel cell activity Monosaccharides 1 sugar Ex Glucose Disaccharides 2 sugars Two monomers joined by a glycosidic linkage a covalent bond formed between two monosaccharides by a dehydration reaction Produced through condensation reactions dehydration synthesis used to join monomers to make polymers Ex Lactose
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