ACS BIOCHEMISTRY COMPREHENSIVE
TEST SCRIPT 2026 QUESTIONS WITH
SOLUTIONS 100% CORRECT.
◍ What accounts for water's unique properties? Answer- Hydrogen
bonding
◍ The unique properties of water (specific heat, heat of vaporization,
solubility). Answer- 1) high specific heat, or heat required to raise the
temperature of the unit mass of a given substance by one degree.
For water to increase in temperature, water molecules must be made to
move faster, or get higher KE, and doing this requires breaking
hydrogen bonds, which absorbs heat. So, as heat is applied, most of it
goes to breaking the bonds not upregulating KE, thus making water
harder to heat than substances where no bonds need to be broken.
2) High heat of vaporization, or the amount of heat needed to turn one g
of a liquid into vapor, without a temperature rise in the liquid. Important
for sweat because it ensures that when the liquid evaporates from our
skin, the heat required for the transition is kept in the gas, causing a net
cooling effect on the skin.
3) Unique solubility properties: "like dissolves like". Water dissolves
polar molecules and ions, and can act as an H-bond donor or receptor
,4) Amphoteric, it can act as an acid (donating electrons) or a base
(accepting electrons). The conjugate acid of water is the hydronium ion,
H3O+, and the conjugate base of water is the hydroxide ion, OH-.
◍ Keq for water at 25 degrees C and in pure water. Answer- At 25
degrees C:
Keq= Kw= [OH-][H3O+]= 1*10^-14
In pure water:
[OH-]=[H3O+]= 1*10^-7
◍ Calculation for pH and pKa. Answer- pH= -log[H3O+]
pKa= -log(Ka)
◍ Normal blood pH range. Answer- 7.35-7.45
◍ The Hydrophobic Effect. Answer- When non-polar molecules
aggregate in the presence of water, minimizing the entropy decrease
water must go through to order themselves around the border of the non-
polar molecule. Reducing the surface area water must organize around
increases entropy, which is favorable.
,The aggregation is responsible for the formation of a variety of lipid
structures in the body, including cell membranes.
◍ Buffers. Answer- Composed of a weak acid (HA) and its conjugate
base (A-). Added acid reacts with A-, and added base reacts with HA,
giving a limited overall pH change.
Two main reactions:
1) When excess base is added:
OH-+HA-->H2O+A-
2) When excess acid is added:
H+ + A- -->HA
**So, the net result is more of the weak acid and its conjugate base**
◍ When are buffers optimal? What equation can we use for this?
Answer- When [HA]= [A-], occurring when pH=pKa
Henderson- Hasselbalch allows use to calculate pH at given pKa, and
vice versa:
◍ Blood Buffering. Answer- Components:
1) carbonic acid (H2CO3) (weak acid). pKa= 6.1.
, 2) Bicarbonate Ion (HCO3-), conjugate base of carbonic acid
3) H+ (hydrogen ion)
If OH- (base) is added, Carbonic acid buffers it into bicarbonate ion and
water.
If H+ (acid) is added, bicarbonate ions and H+ buffer it to carbonic acid.
◍ Amino Acids, peptides, and polypeptides. Answer- the building
blocks of proteins, a chain of which is called a peptide. There are 20
standard amino acids that act as the monomers to make protein
polymers!
A long peptide is called a polypeptide!
Proteins are composed of one or more polypeptide chain.
◍ Peptide bonds. Answer- Between the C and N of C=O and N-H of two
adjacent amino acids.
◍ What wavelength is indicative of aromatic amino acids? Answer- 280
nm, with tryptophan absorbing more, tyrosine absorbing a bit less, and
phenylalanine absorbing a lot less.
TEST SCRIPT 2026 QUESTIONS WITH
SOLUTIONS 100% CORRECT.
◍ What accounts for water's unique properties? Answer- Hydrogen
bonding
◍ The unique properties of water (specific heat, heat of vaporization,
solubility). Answer- 1) high specific heat, or heat required to raise the
temperature of the unit mass of a given substance by one degree.
For water to increase in temperature, water molecules must be made to
move faster, or get higher KE, and doing this requires breaking
hydrogen bonds, which absorbs heat. So, as heat is applied, most of it
goes to breaking the bonds not upregulating KE, thus making water
harder to heat than substances where no bonds need to be broken.
2) High heat of vaporization, or the amount of heat needed to turn one g
of a liquid into vapor, without a temperature rise in the liquid. Important
for sweat because it ensures that when the liquid evaporates from our
skin, the heat required for the transition is kept in the gas, causing a net
cooling effect on the skin.
3) Unique solubility properties: "like dissolves like". Water dissolves
polar molecules and ions, and can act as an H-bond donor or receptor
,4) Amphoteric, it can act as an acid (donating electrons) or a base
(accepting electrons). The conjugate acid of water is the hydronium ion,
H3O+, and the conjugate base of water is the hydroxide ion, OH-.
◍ Keq for water at 25 degrees C and in pure water. Answer- At 25
degrees C:
Keq= Kw= [OH-][H3O+]= 1*10^-14
In pure water:
[OH-]=[H3O+]= 1*10^-7
◍ Calculation for pH and pKa. Answer- pH= -log[H3O+]
pKa= -log(Ka)
◍ Normal blood pH range. Answer- 7.35-7.45
◍ The Hydrophobic Effect. Answer- When non-polar molecules
aggregate in the presence of water, minimizing the entropy decrease
water must go through to order themselves around the border of the non-
polar molecule. Reducing the surface area water must organize around
increases entropy, which is favorable.
,The aggregation is responsible for the formation of a variety of lipid
structures in the body, including cell membranes.
◍ Buffers. Answer- Composed of a weak acid (HA) and its conjugate
base (A-). Added acid reacts with A-, and added base reacts with HA,
giving a limited overall pH change.
Two main reactions:
1) When excess base is added:
OH-+HA-->H2O+A-
2) When excess acid is added:
H+ + A- -->HA
**So, the net result is more of the weak acid and its conjugate base**
◍ When are buffers optimal? What equation can we use for this?
Answer- When [HA]= [A-], occurring when pH=pKa
Henderson- Hasselbalch allows use to calculate pH at given pKa, and
vice versa:
◍ Blood Buffering. Answer- Components:
1) carbonic acid (H2CO3) (weak acid). pKa= 6.1.
, 2) Bicarbonate Ion (HCO3-), conjugate base of carbonic acid
3) H+ (hydrogen ion)
If OH- (base) is added, Carbonic acid buffers it into bicarbonate ion and
water.
If H+ (acid) is added, bicarbonate ions and H+ buffer it to carbonic acid.
◍ Amino Acids, peptides, and polypeptides. Answer- the building
blocks of proteins, a chain of which is called a peptide. There are 20
standard amino acids that act as the monomers to make protein
polymers!
A long peptide is called a polypeptide!
Proteins are composed of one or more polypeptide chain.
◍ Peptide bonds. Answer- Between the C and N of C=O and N-H of two
adjacent amino acids.
◍ What wavelength is indicative of aromatic amino acids? Answer- 280
nm, with tryptophan absorbing more, tyrosine absorbing a bit less, and
phenylalanine absorbing a lot less.
