ACS Biochemistry Exam Study
Questions and Answers with Verified
Solutions Graded A 2024
POSSIBLEA
.
.
,Metabolism (catabolism and Mutation: during growth and
anabolism) - Metabolism: sum of total reproduction, cells sometimes make
chemical reactions in an organism, mistakes, leading to mutations and
also the method by which cells extract evolution.
and use energy from their
environment.
Respond to environment: metabolic
pathways respond to signals,
Catabolism: The process by which including light, touch, hormones, and
stored nutrients and ingested foods are nutrients, that can turn the pathways
converted to a usable form of energy. on or off.
It produces simple products CO2,
H2O, NH3, and building blocks such
as sugars and fats that are used in Speed and efficiency: cell operations
anabolism. are highly specific to maximize
targeting and efficiency.
Anabolism: the process by which
simple products and building blocks Similar building blocks: most species
of catabolism are used to create are very similar at the cellular level.
complex biological products that
contribute to organismal growth and
development. It also uses the energy What accounts for water's unique
produced in catabolism to do properties? - Hydrogen bonding
biological work.
The unique properties of water
Properties of cells - Metabolism: (specific heat, heat of vaporization,
undergoing catabolic and anabolic solubility) - 1) high specific heat, or
processes. heat required to raise the temperature
of the unit mass of a given substance
by one degree.
Reproduction: cell populations grow For water to increase in temperature,
via asexual reproduction. 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 In pure water:
the bonds not upregulating KE, thus
[OH-]=[H3O+]= 1*10^-7
making water harder to heat than
substances where no bonds need to be
broken. Calculation for pH and pKa - pH= -
log[H3O+]
2) High heat of vaporization, or the pKa= -log(Ka)
amount of heat needed to turn one g
of a liquid into vapor, without a
temperature rise in the liquid. Normal blood pH range - 7.35-7.45
Important for sweat because it ensures
that when the liquid evaporates from
our skin, the heat required for the The Hydrophobic Effect - When non-
transition is kept in the gas, causing a polar molecules aggregate in the
net cooling effect on the skin. presence of water, minimizing the
entropy decrease water must go
through to order themselves around
3) Unique solubility properties: "like the border of the non-polar molecule.
dissolves like". Water dissolves polar Reducing the surface area water must
molecules and ions, and can act as an organize around increases entropy,
H-bond donor or receptor which is favorable.
4) Amphoteric, it can act as an acid The aggregation is responsible for the
(donating electrons) or a base formation of a variety of lipid
(accepting electrons). The conjugate structures in the body, including cell
acid of water is the hydronium ion, membranes.
H3O+, and the conjugate base of
water is the hydroxide ion, OH-.
Buffers - Composed of a weak acid
(HA) and its conjugate base (A-).
Keq for water at 25 degrees C and in Added acid reacts with A-, and added
pure water - At 25 degrees C: base reacts with HA, giving a limited
overall pH change.
Keq= Kw= [OH-][H3O+]= 1*10^-14
, Two main reactions: If H+ (acid) is added, bicarbonate ions
and H+ buffer it to carbonic acid.
1) When excess base is added:
OH-+HA-->H2O+A-
Amino Acids, peptides, and
2) When excess acid is added:
polypeptides - the building blocks of
H+ + A- -->HA proteins, a chain of which is called a
peptide. There are 20 standard amino
acids that act as the monomers to
**So, the net result is more of the make protein polymers!
weak acid and its conjugate base**
A long peptide is called a
When are buffers optimal? What polypeptide!
equation can we use for this? - When
[HA]= [A-], occurring when pH=pKa
Proteins are composed of one or more
polypeptide chain.
Henderson- Hasselbalch allows use to
calculate pH at given pKa, and vice
versa: Peptide bonds - Between the C and N
of C=O and N-H of two adjacent
amino acids.
Blood Buffering - Components:
1) carbonic acid (H2CO3) (weak
acid). pKa= 6.1. What wavelength is indicative of
aromatic amino acids? - 280 nm, with
2) Bicarbonate Ion (HCO3-), tryptophan absorbing more, tyrosine
conjugate base of carbonic acid absorbing a bit less, and
3) H+ (hydrogen ion) phenylalanine absorbing a lot less.
If OH- (base) is added, Carbonic acid Stereochemistry of amino acids -
buffers it into bicarbonate ion and Every carbon except for glycine is a
water. chiral center, giving two possible
structures for each: L and D (except
for glycine).
