Bio 311C Final Exam Review

Bio 311C Final Exam Review -...

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1.  Covalent bond -two atoms share a pair of electrons. Strongest of all bonds and present in all compounds and molecules. Nonpolar covalent bonding occurs when two atoms with equal or similar electronegativities share electrons equally. Polar covalent bonding occurs when two atoms share electrons unequally. Ex: glycosidic bonds of carbohydrates, ester bonds of lipids, peptide bonds of proteins, and phosphodiester bonds of DNA/RNA. Ionic bond -when the electronegativity of one atom is greater than that of the adjoining atom, the one with higher electronegativity pulls electrons to its valence shell from its neighboring atoms, forming a cation and anion. Ex: B/w + and – charged amino acids H-bonding -the hydrogen covalently attached to one electronegative atom is attracted to another electronegative atom. Ex: Attraction b/w water molecules, between H 2 0 and NH 3 , and the H-bonds of DNA, RNA, and proteins. Van der Waals -Occurs in nonpolar molecule interaction; pockets of constantly changing + and – charges due to changing distribution of e- clouds. Ex: lipids in bio membranes and cellulose in plant cell walls. Hydrophilic/phobic -Hydrophilic are normally polar, charged molecules that are water- soluble; hydrophobic are normally nonpolar, lipid-soluble Ex: phospholipids in bio membranes have a hydrophilic region outside membrane bilayer that interacts w/aqueous environment and a hydrophobic region inside the membrane bilayer; amino acids with hydrophobic side chains tend to be inside of the protein and hydrophilic side chains in the interior or exterior portion. 2.  Acid -Chemical that dissociates in a soln and increases [H+]/decreases pH; H+ donor Ex: HCL->H+ + Cl- Base -Chemical that acts as either a H+ acceptor (decreases H+) or OH- donor (increase OH-) Ex: NaOH->Na + + OH- and then OH- + H+->H 2 0; NH3 + H+-> NH4+ Buffers -Substance that maintains pH; accepts protons when pH is low and donates pH when pH is high. Most buffers are weak acids/bases. Ex: pH increases, carbonic acid (H2CO3) donates protons to become bicarbonate, a base, HCO3- pH 7 is neutral pH 0-6 is acidic, below 0 is considered an acid. pH 8-14 is basic, above 14 is considered a base. 3.  Hydroxyl group (-OH)-Makes molecule water-soluble. Molecules w/OH groups are generally called alcohols. Ex: Carbs, proteins, and nucleic acids contain OH groups (sugars and alcohols). Carbonyl group (C=O)-nonpolar, end of molecule is an aldehyde (glucose); middle of molecule is ketone (fructose).
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Ex: propanol, acetone, glucose, fructose; simple sugars, some proteins and nucleotides Carboxyl group (COOH)-acidic; can ionize and increase H+ in soln. Ionized forms have -ate at the end (citric acid->citrate). Ex:
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This note was uploaded on 12/31/2009 for the course BIO 311C taught by Professor Satasivian during the Spring '08 term at University of Texas.

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Bio 311C Final Exam Review -...

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