BCH 451 EXAM #1 QUESTIONS WITH COMPLETE VERIFIED
ANSWERS 100% GUARANTEED PASS 2024/2025
Six most abundant elements in living organisms
Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus & Sulfure
Most Mass %: O, C, H, N, P, S
# of Atoms %: H, O, C, N, P
Five essential ions in all living organisms
Calcium, Potassium, Sodium, Magnesium, Chloride
Covalent Bonding
Atoms sharing outer shell electrons to completely fill each atoms outer shell.
Strength: related to difference in atom electronegativity
Ionic Bonding
Transfer of electrons from one atom to the other creating charged ions
Dipole Moment
Uneven distribution of electrons in the atoms. The uneven charge distribution creates regions that are
positive and negative in the molecule which can become electrophiles and nucleophiles. Charges also
serve to attract and interact with other molecules of opposite charge.
Hydrophilic
Polar compounds soluble in polar solvents (most biological molecules are soluble in water or hydrophilic)
,Hydrophobic
Non-polar molecules (non-charged, lacking electronegative atoms, aliphatic carbon chains or aromatic
rings)
Hydrophobic effect
Tendency for non-polar molecules to coalesce or group together. Ordering of polar water molecules
around non-polar molecules is minimized when multiple non-polar molecules group together. Entropy
driven.
Hydration
stabilizes cations/anions by weakening their electrostatic interactions thus disrupting crystallization.
Structure of water
Tetrahedral: oxygen is buried in the center of the tetrahedron and the 4 corners are occupied by the 2
hydrogens and 2 unbounded electron pairs from oxygen.
Angle: 104.5
Hydrogen Bonding
Weak attraction between a slightly positive hydrogen atom (covalently bonded to an electronegative
atom) and a slightly negative atom.
VERY WEAK intermolecular interaction
Critical Features of a Hydrogen Bond
1. Defined Length: 2.8-3.0A
2. Linear Positioning
Keq of water
,[products]/[reactants]
[H+][OH-]/[H2O] where [H2O] = 55.5 which is so large that is does not change as pH changes so constant.
SO Keq = [H+]x[OH-]
pH of H2O (solvent)
Equilibrium of hydrogen and hydroxyl ions
pH = -log10[H+]
Physiological salt concentration [NaCl]
.14M
Physiological pH
7.4
Acid
proton donor, protonated
Base
proton acceptor, ionized
Strong Acid
Acid that completely dissociates in H2O solution
Weak Acid
Acid that partially dissociates in H2O solution
Conjugate acid/conjugate base
, Acid: has H
Base: No H or is negatively charged
Henderson-Hasselback Equation
pH = pKa + log[A-]/[HA]
[A-] = conjugate base
[HA] = conjugate acid
Below pKa a weak acid is
Protonated
Above pKa a weak acid is
ionized
Titration curve: ratio of [A-]/[HA] equals number of transition points
# of ionizable protons equals # of regions of buffering capacity around each pKa
Carbon
The chemistry of living organisms is organized around carbon. Carbon has 4 outer shell electrons that is
can share to establish covalent bonds with other atoms
Aliphatic
Carbon-carbon chains, non-polar and hydrophobic
Rate of Reaction
ANSWERS 100% GUARANTEED PASS 2024/2025
Six most abundant elements in living organisms
Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus & Sulfure
Most Mass %: O, C, H, N, P, S
# of Atoms %: H, O, C, N, P
Five essential ions in all living organisms
Calcium, Potassium, Sodium, Magnesium, Chloride
Covalent Bonding
Atoms sharing outer shell electrons to completely fill each atoms outer shell.
Strength: related to difference in atom electronegativity
Ionic Bonding
Transfer of electrons from one atom to the other creating charged ions
Dipole Moment
Uneven distribution of electrons in the atoms. The uneven charge distribution creates regions that are
positive and negative in the molecule which can become electrophiles and nucleophiles. Charges also
serve to attract and interact with other molecules of opposite charge.
Hydrophilic
Polar compounds soluble in polar solvents (most biological molecules are soluble in water or hydrophilic)
,Hydrophobic
Non-polar molecules (non-charged, lacking electronegative atoms, aliphatic carbon chains or aromatic
rings)
Hydrophobic effect
Tendency for non-polar molecules to coalesce or group together. Ordering of polar water molecules
around non-polar molecules is minimized when multiple non-polar molecules group together. Entropy
driven.
Hydration
stabilizes cations/anions by weakening their electrostatic interactions thus disrupting crystallization.
Structure of water
Tetrahedral: oxygen is buried in the center of the tetrahedron and the 4 corners are occupied by the 2
hydrogens and 2 unbounded electron pairs from oxygen.
Angle: 104.5
Hydrogen Bonding
Weak attraction between a slightly positive hydrogen atom (covalently bonded to an electronegative
atom) and a slightly negative atom.
VERY WEAK intermolecular interaction
Critical Features of a Hydrogen Bond
1. Defined Length: 2.8-3.0A
2. Linear Positioning
Keq of water
,[products]/[reactants]
[H+][OH-]/[H2O] where [H2O] = 55.5 which is so large that is does not change as pH changes so constant.
SO Keq = [H+]x[OH-]
pH of H2O (solvent)
Equilibrium of hydrogen and hydroxyl ions
pH = -log10[H+]
Physiological salt concentration [NaCl]
.14M
Physiological pH
7.4
Acid
proton donor, protonated
Base
proton acceptor, ionized
Strong Acid
Acid that completely dissociates in H2O solution
Weak Acid
Acid that partially dissociates in H2O solution
Conjugate acid/conjugate base
, Acid: has H
Base: No H or is negatively charged
Henderson-Hasselback Equation
pH = pKa + log[A-]/[HA]
[A-] = conjugate base
[HA] = conjugate acid
Below pKa a weak acid is
Protonated
Above pKa a weak acid is
ionized
Titration curve: ratio of [A-]/[HA] equals number of transition points
# of ionizable protons equals # of regions of buffering capacity around each pKa
Carbon
The chemistry of living organisms is organized around carbon. Carbon has 4 outer shell electrons that is
can share to establish covalent bonds with other atoms
Aliphatic
Carbon-carbon chains, non-polar and hydrophobic
Rate of Reaction
