Biology 1201: Exam 1 study guideChemical 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, respectively.Attraction only exists when there are oppositely charged particles.Ionic Bonds: 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.Covalent Bonds:Share electrons.Pure/nonpolar covalent- shared equally. No polarity. The electrons spend the same amount of time orbiting each nucleus.Polar Covalent – Shared unequally. Partial charges. Spend more time orbiting one nucleus than 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 0.5-1.7Polarity: 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.Weak Bonds:Not involved in the making of a substance. They’re within/between moleculesOccur between different molecules.Hydrogen bonds: Type of weak bond. Weak attractions between atoms on different molecules or different parts of a large molecule. Molecules interact but don’t fuse. Always involves hydrogen.Water:Hydrogen: partial + chargeOxygen: 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:Compound: A substance consisting of two or more different atoms in specific proportions, bounded together in a specific pattern.Molecule: Smallest unit of a compound that retains all properties of that compound. (Ex: a singlewater 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:CO₂HExact 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. H₂O (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 10²³Moles and Molar Concentrations:1 mole: The mass of a substance equal to its gram molecular weight (1 mole of water = 18 grams).Acids: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)Bases:Reduce the hydrogen ion concentration.Dissociate to produce hydroxide ions.Basic solutions- contain a higher OH- concentration than H+pH scale: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, which is a 2).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 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: Nonpolar:Hydroxyl SulfhydrylCarbonyl MethylCarboxyl* C-HAminoPhosphate** = Acidic.Hydroxyl group:Polar.-OHCarbonyl 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=OAcids: Amino Acids. Carboxyl groups make them into acids. Theyadd polarity by releasing hydrogen ions in a solution. Make up organic acids and are found in cells in an ionized formwith a 1(-) chargeCOOH Acts like acid: ionizesAmino group:H-N-HAmino Acids: (H3N+)/(H2N+)Phosphate group:Commonly used in cells to transfer one organic molecule to another.Acidic. O |O=P-OH | OHPolar covalent bonds- lots of polarity.2 hydroxide groups dissociate, leading to the release ofhydrogen ions, making it Acidic.Found in DNA and RNA Has the potential to react with water, releasing energy andgives a molecule a (-) chargeSulfhydryl group:-SHNonpolar.Found in Cyteine (Amino Acid) 2 of them can form covalent bonds with each other and forms cysteines. Methyl group:-CH3Nonpolar.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.”CarbohydratesCompounds 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 sugars. Function in animals: metabolic fuel (glucose and sucrose), chitin (exoskeleton of many arthropods), and storage (starch) Sugar molecules that fuel cell activity.Monosaccharides: 1
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