ACS BIOCHEMISTRY PRACTICE FINAL
PRACTICE QUESTIONS WITH DETAILED
EXPLANATIONS 2026
◉ Properties of cells.
Answer: Metabolism: undergoing catabolic and anabolic processes.
Reproduction: cell populations grow via asexual reproduction.
Mutation: during growth and reproduction, cells sometimes make
mistakes, leading to mutations and evolution.
Respond to environment: metabolic pathways respond to signals,
including light, touch, hormones, and nutrients, that can turn the
pathways on or off.
Speed and efficiency: cell operations are highly specific to maximize
targeting and efficiency.
Similar building blocks: most species are very similar at the cellular
level.
,◉ 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
PRACTICE QUESTIONS WITH DETAILED
EXPLANATIONS 2026
◉ Properties of cells.
Answer: Metabolism: undergoing catabolic and anabolic processes.
Reproduction: cell populations grow via asexual reproduction.
Mutation: during growth and reproduction, cells sometimes make
mistakes, leading to mutations and evolution.
Respond to environment: metabolic pathways respond to signals,
including light, touch, hormones, and nutrients, that can turn the
pathways on or off.
Speed and efficiency: cell operations are highly specific to maximize
targeting and efficiency.
Similar building blocks: most species are very similar at the cellular
level.
,◉ 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
