MCB 250 exam 1 WITH
QUESTIONS AND
ANSWERS
Primary life elemets ANSWER✔ � -CHNOPS
Covalent bonds ANSWER✔ � --Strongest type of Chemical bond
-Examples include guanine and DNA
-Sharing electrons
-Bond angles fixed
prokaryotes ANSWER✔ � -bacteria and archaea with membrane
Eukaryotes ANSWER✔ � -No membrane. Mainly multicelluar
,Ionic Bonds ANSWER✔ � --Weaker than covalent, but still relatively strong
-Opposite charges attract
-Large electronegativity difference.
-electrostatic
-not directional
-Ex:Bond between Lysine and Aspartate, dsDNA and Mg2+
Hydrogen Bonds ANSWER✔ � --double helix in DNA are held together by hydrogen bonds between
hydrogen atoms attached to nitrogen on one strand, and lone pairs on another nitrogen or an oxygen on
the other one.
-Weaker than ionic.
-Appears btwn two polar covalent bonds.
-i.e. two water molecules, two parts of one large molecule
Van der waals forces ANSWER✔ � --All electron clouds attract each other very weakly.
-Effect is distance dependent
-Add enough together and it can be significant.
-Only significant when two molecules fit over a large surface.
-causes aro rings to stack
-I.e. protein structure.
dsDNA ANSWER✔ � -Dont forget its negatively charged.
Interaction in base stacking ANSWER✔ � -Van der waals
Interaction btwn dsDNA and Mg2+ ANSWER✔ � -Ionic bond
,Interaction btwn two non polar groups in water? ANSWER✔ � -Van der waals.
Hydrophobic ANSWER✔ � --Molecules w/o a dipole moment (nonpolar) are excluded by H2O.
-I.e. Stearic Acid-C18
Amphiphatic molecules ANSWER✔ � -Have both hydrophobic and hydrophilic regions.
i.e. Phosphatidyl choline-(fatty acid tail hydrophobic)
Hydrophobic interactions drive formation of a lipid bilayer ANSWER✔ � --hydrophilic heads stay
outside while hydrophobic tails go inside
aromatic rings ANSWER✔ � -resonance structure, every other carbon double bonded, electrons shared
equally (delocalized), uv absorbance.
conjugated double bonds ANSWER✔ � -no rotation, because a bond and a half, alternating single and
double bonds, uv absorbance
Absorption of Light by aro rings ANSWER✔ � --All molecules absorb radiation
-Electron orbitals are "quantized"
-Light of the appropriate energy can kick electrons into a higher orbit
-Abs Spectrum provides info on structure.
-Aro rings can absorb light in the uv range.
Single carbon bonds can do... ANSWER✔ � --gives shape to organic molecules
-Rotate
, Triple bonds ANSWER✔ � --Same as double bonds in being rigid.
DNA and RNA light absorbance ANSWER✔ � -260nm, amino acid tryptophan absorbs light at 280nm
More on H-bonds. ANSWER✔ � -hydrogen bonds covalently to O and N
- DIRECTIONAL( stronger if the bond is lined up straight)
High Energy bonds ANSWER✔ � -Release significant amount of energy if broken
Acids ANSWER✔ � -proton donors
Bases ANSWER✔ � -proton acceptors
Degree of acidity or basicity of an aqueous solution is determined by measuring... ANSWER✔ � -H+
ph ANSWER✔ � -pH=-logH+
protonation ANSWER✔ � -the addition of a proton (H+) to an atom, molecule, or ion, forming the
conjugate acid
-i.e. the protonation of water by sulfuric acid:
H2SO4 + H2O ⇌ H3O+ + HSO4−
Deprotonation ANSWER✔ � -the removal (transfer) of a proton (a hydrogen cation, H+)
NH3+⇌ NH2 + H+
QUESTIONS AND
ANSWERS
Primary life elemets ANSWER✔ � -CHNOPS
Covalent bonds ANSWER✔ � --Strongest type of Chemical bond
-Examples include guanine and DNA
-Sharing electrons
-Bond angles fixed
prokaryotes ANSWER✔ � -bacteria and archaea with membrane
Eukaryotes ANSWER✔ � -No membrane. Mainly multicelluar
,Ionic Bonds ANSWER✔ � --Weaker than covalent, but still relatively strong
-Opposite charges attract
-Large electronegativity difference.
-electrostatic
-not directional
-Ex:Bond between Lysine and Aspartate, dsDNA and Mg2+
Hydrogen Bonds ANSWER✔ � --double helix in DNA are held together by hydrogen bonds between
hydrogen atoms attached to nitrogen on one strand, and lone pairs on another nitrogen or an oxygen on
the other one.
-Weaker than ionic.
-Appears btwn two polar covalent bonds.
-i.e. two water molecules, two parts of one large molecule
Van der waals forces ANSWER✔ � --All electron clouds attract each other very weakly.
-Effect is distance dependent
-Add enough together and it can be significant.
-Only significant when two molecules fit over a large surface.
-causes aro rings to stack
-I.e. protein structure.
dsDNA ANSWER✔ � -Dont forget its negatively charged.
Interaction in base stacking ANSWER✔ � -Van der waals
Interaction btwn dsDNA and Mg2+ ANSWER✔ � -Ionic bond
,Interaction btwn two non polar groups in water? ANSWER✔ � -Van der waals.
Hydrophobic ANSWER✔ � --Molecules w/o a dipole moment (nonpolar) are excluded by H2O.
-I.e. Stearic Acid-C18
Amphiphatic molecules ANSWER✔ � -Have both hydrophobic and hydrophilic regions.
i.e. Phosphatidyl choline-(fatty acid tail hydrophobic)
Hydrophobic interactions drive formation of a lipid bilayer ANSWER✔ � --hydrophilic heads stay
outside while hydrophobic tails go inside
aromatic rings ANSWER✔ � -resonance structure, every other carbon double bonded, electrons shared
equally (delocalized), uv absorbance.
conjugated double bonds ANSWER✔ � -no rotation, because a bond and a half, alternating single and
double bonds, uv absorbance
Absorption of Light by aro rings ANSWER✔ � --All molecules absorb radiation
-Electron orbitals are "quantized"
-Light of the appropriate energy can kick electrons into a higher orbit
-Abs Spectrum provides info on structure.
-Aro rings can absorb light in the uv range.
Single carbon bonds can do... ANSWER✔ � --gives shape to organic molecules
-Rotate
, Triple bonds ANSWER✔ � --Same as double bonds in being rigid.
DNA and RNA light absorbance ANSWER✔ � -260nm, amino acid tryptophan absorbs light at 280nm
More on H-bonds. ANSWER✔ � -hydrogen bonds covalently to O and N
- DIRECTIONAL( stronger if the bond is lined up straight)
High Energy bonds ANSWER✔ � -Release significant amount of energy if broken
Acids ANSWER✔ � -proton donors
Bases ANSWER✔ � -proton acceptors
Degree of acidity or basicity of an aqueous solution is determined by measuring... ANSWER✔ � -H+
ph ANSWER✔ � -pH=-logH+
protonation ANSWER✔ � -the addition of a proton (H+) to an atom, molecule, or ion, forming the
conjugate acid
-i.e. the protonation of water by sulfuric acid:
H2SO4 + H2O ⇌ H3O+ + HSO4−
Deprotonation ANSWER✔ � -the removal (transfer) of a proton (a hydrogen cation, H+)
NH3+⇌ NH2 + H+
