ACS Biochemistry Newest Exam Detailed
Questions and Answers Verified Solutions
Latest Update 2026/2027
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
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.
■ Stereochemistry of amino acids
Answer:
, Every carbon except for glycine is a chiral center, giving two possible structures for each: L and D
(except for glycine).
L is the only one found in nature.
■ Acid-Base properties of amino acids
Answer:
Each has at least two ionizable protons (from the COOH and NH3 groups), but most have others.
COOH pKa: 2.34
NH3 pKa: 29.60
■ PI
Answer:
the isoelectric point, or the pH at which an amino acid or peptide has no net charge.
- At pH= PI, the predominant species is the zwitterion
- At pH<PI, the predominant species is net positive
- At pH>PI, the predominant species is net negative
**At PI, amino acid or peptide cannot migrate through an electric field, so this is a way we can
separate amino acids (by PI via electric field!)**
■ How to calculate PI, or isoelectric pint
Answer:
Average pKa values involving the neutral species
For glycine, that only has COOH and NH3 pKa's, the PI is the average between 2.34 and 9.60, so
5.97!
■ Essential Amino Acids
Answer:
Those that cannot be made in the body and thus must be obtained via the diet. Some can be made
from others, so it isn't a hard line, but:
Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, and
Valine are all essential.
**Cysteine can be made from methionine, tyrosine can be made from phenylalanine, etc.**
■ Amino acid name post-peptide bond
Answer:
Questions and Answers Verified Solutions
Latest Update 2026/2027
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
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.
■ Stereochemistry of amino acids
Answer:
, Every carbon except for glycine is a chiral center, giving two possible structures for each: L and D
(except for glycine).
L is the only one found in nature.
■ Acid-Base properties of amino acids
Answer:
Each has at least two ionizable protons (from the COOH and NH3 groups), but most have others.
COOH pKa: 2.34
NH3 pKa: 29.60
■ PI
Answer:
the isoelectric point, or the pH at which an amino acid or peptide has no net charge.
- At pH= PI, the predominant species is the zwitterion
- At pH<PI, the predominant species is net positive
- At pH>PI, the predominant species is net negative
**At PI, amino acid or peptide cannot migrate through an electric field, so this is a way we can
separate amino acids (by PI via electric field!)**
■ How to calculate PI, or isoelectric pint
Answer:
Average pKa values involving the neutral species
For glycine, that only has COOH and NH3 pKa's, the PI is the average between 2.34 and 9.60, so
5.97!
■ Essential Amino Acids
Answer:
Those that cannot be made in the body and thus must be obtained via the diet. Some can be made
from others, so it isn't a hard line, but:
Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, and
Valine are all essential.
**Cysteine can be made from methionine, tyrosine can be made from phenylalanine, etc.**
■ Amino acid name post-peptide bond
Answer:
