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Biochemistry Midterm Exam Review

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  • What family of organic compounds does a molecule with only carbon and hydrogen atoms and one carbon–carbon double bond belong to?
    It is an alkene, a type of hydrocarbon with at least one carbon–carbon double bond.
  • How is an alcohol identified in organic compounds?
    An alcohol contains an oxygen atom with a single bond to a hydrogen atom (–OH group) bonded to a tetravalent carbon.
  • What defines an aromatic hydrocarbon compound?
    A six-membered ring with alternating carbon–carbon single and double bonds, often called a benzene ring, defines an aromatic hydrocarbon.
  • How is a ketone functional group characterized?
    A ketone has a carbon–oxygen double bond (carbonyl) connected to two carbon atoms, with no singly bonded oxygen or nitrogen attached to the carbonyl carbon.
  • What functional groups are present in a molecule with both an amide and an amine?
    An amide group has a carbonyl bonded to an –NH2, and an amine group contains an –NH2 not bonded to a carbonyl.
  • What functional groups are indicated by a ring with alternating single and double bonds and an S–S bond?
    The ring is an aromatic hydrocarbon, and the S–S bond indicates a disulfide group.
  • What is the general formula and structure of an amine with formula C2H7N?
    An amine contains a C–NH2 group; for C2H7N, two carbons are bonded together with an –NH2 attached to one carbon and hydrogens filling remaining bonds.
  • What characterizes an alkyne with formula C3H4?
    An alkyne contains a carbon–carbon triple bond; for C3H4, two carbons form a triple bond, and the third carbon is bonded to one of these with hydrogens filling remaining bonds.
  • What is the structure of an ether with formula C4H10O?
    An ether contains a C–O–C group; for C4H10O, two carbons are bonded on either side of oxygen, with remaining hydrogens filling carbon valences.
  • Which characteristics are typical of organic compounds?
    Organic compounds typically have low melting points, are not soluble in water, burn easily in air, and have covalent bonds.
  • Which of the following contains only organic compounds: CH3OH, H2SO4, KCl; C4H10, CH3COOH, CH3OH; KCl, C4H10, CH3COOH; or CH3CH2CH2Cl, KCl, NaCl?
    Only C4H10, CH3COOH, CH3OH contains exclusively organic compounds.
  • What is the physical state of octane (C8H18) at room temperature?
    Octane is most likely a liquid at room temperature.
  • What are the products of octane combustion?
    Complete combustion of octane produces CO2 and H2O.
  • Which property is NOT typical of hydrocarbons?
    Hydrocarbons are generally nonpolar, so being polar is not typical.
  • What is the product of the hydration reaction of an alkene with water in the presence of acid?
    The product is an alcohol.
  • How can you identify if two structures with formula C7H16 represent the same molecule?
    Check the longest carbon chain and the position of branches; identical chains and branch positions indicate the same molecule (conformers).
  • What is the primary difference between isomers and conformers?
    Isomers have different connectivity of atoms; conformers differ only by rotation around single bonds.
  • How do you convert a condensed structure to a line structure?
    Draw a zigzag line representing the longest carbon chain; add branches as lines off the main chain; show all non-carbon atoms explicitly.
  • What type of reaction is hydrogenation of an alkene?
    Hydrogenation is an addition reaction where H2 adds across the double bond.
  • What is the role of water in the reaction of ammonia with water?
    Water acts as an acid donating a hydrogen ion to ammonia, which acts as a base.
  • How is an ester formed from a carboxylic acid and an alcohol?
    By removing –OH from the acid and –H from the alcohol to form water, then joining the remaining fragments with a single bond.
  • What are the products of acid-catalyzed hydrolysis of an ester like ethyl formate?
    The products are a carboxylic acid and an alcohol.
  • How do you classify amino acids as polar or nonpolar?
    Amino acids with nonpolar side chains (e.g., glycine) are nonpolar; those with polar side chains (e.g., threonine) are polar.
  • What stabilizes the alpha helix and beta-pleated sheet secondary protein structures?
    Hydrogen bonds between backbone nitrogen and carbonyl oxygen atoms stabilize secondary structures.
  • What types of interactions stabilize tertiary protein structure?
    Tertiary structure is stabilized by hydrophobic interactions, disulfide bonds, ionic bonds, and hydrogen bonds between R groups.
  • What is the difference between primary, secondary, tertiary, and quaternary protein structures?
    Primary is amino acid sequence; secondary is local folding (alpha helix, beta sheet); tertiary is 3D folding of one chain; quaternary is assembly of multiple chains.
  • What effect do pH and temperature changes have on enzyme activity?
    Deviations from optimum pH or temperature generally decrease enzyme activity.
  • How do competitive and noncompetitive enzyme inhibitors differ?
    Competitive inhibitors bind the active site and can be overcome by more substrate; noncompetitive bind elsewhere and cannot be overcome by substrate.