ACS BIOCHEMISTRY EXAM 2024 ACTUAL EXAM
COMPLETE 250 QUESTIONS WITH DETAILED VERIFIED
ANSWERS (100% CORRECT ANSWERS) / ALREADY
GRADED A+
Metabolism (catabolism and anabolism) ANSWER>>>>Metabolism: sum of total chemical
reactions in an organism, also the method by which cells extract and use energy
from their environment.
Catabolism: The process by which stored nutrients and ingested foods are converted to a usable form of
energy. It produces simple products CO2, H2O, NH3, and building blocks such as sugars and fats that are
used in anabolism.
Anabolism: the process by which simple products and building blocks of catabolism are used to create
complex biological products that contribute to organismal growth and development. It also uses the
energy produced in catabolism to do biological work.
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, whic h 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
