ACS BIOCHEMISTRY EXAM 2026 ACTUAL
EXAM COMPLETE 550 QUESTIONS WITH
DETAILED VERIFIED ANSWERS (100%
CORRECT ANSWERS) / ALREADY
GRADED A+
What fibrous protein are blood vessels made out of, and why? - CORRECT
ANSWER ✔✔- They are mostly elastin. They require the ability to expand and
contract with each heart beat- they must be extensible but also resilient. So,
elastin is the perfect material.
It is common for tissues requiring flexibility to have a network of elastic fibers
interwoven with collagen (the elastic fibers being 50% elastin by mass).
Elastin Structure - CORRECT ANSWER ✔✔- Alternating hydrophilic and
hydrophobic domains give elastin its key ability to stretch and compress like a
rubber band: the hydrophobic domains are like a plate of spaghetti in the related
state- they are gathered away from water.
Upon being stretched, the molecules uncoil into an extended conformation, but
immediately coil back to a hydrophobic clump once the force is removed! This
combination gives elastin its rubber band-like ability.
Elastin Cross-links - CORRECT ANSWER ✔✔- Lysine cross-links ensure the
molecule returns to its original state after stretching.
Pg. 1
,What fibrous protein makes up skin, and why? - CORRECT ANSWER ✔✔- Skin
requires elasticity, resilience, strength, and protection- so keratin is key, along
with elastin and collagen.
Alpha Keratin (what composes, and its fundamental structure) - CORRECT
ANSWER ✔✔- Composes skin, hair, wool, feathers, nails, claws, quills, horns,
hooves, etc.
Fundamental structure is an alpha helix. Two alpha helixes coil together to give a
two-chain coil, which then bovines with another two-chain coil to give a
protofilament, which then further combine to give a protofibril.
Alpha Keratin Cross links - CORRECT ANSWER ✔✔- Helicies and fibers are cross-
linked by disulfide linkages.
When getting a perm, straight hair is given a chemical treatment that reduces the
disulfide bonds to S-H groups, then the desired style is given, then the S-H bonds
are oxidized back to disulfide bonds, in the desired style, holding it in place.
Silk Fibroin structure - CORRECT ANSWER ✔✔- It has the repeating structure GLY-
ALA-GLY-ALA.
It is an anti-parallel (strong) beta sheet, with amorphous regions surrounding
bulky residues.
Fibrous vs. globular proteins - CORRECT ANSWER ✔✔- Fibrous proteins have a
single major type of secondary structure, while most other proteins are folded
compactly and have a mix of secondary structures.
Pg. 2
,Myoglobin - CORRECT ANSWER ✔✔- The oxygen carrying protein of red muscle.
Hemoglobin - CORRECT ANSWER ✔✔- The oxygen carrying protein of the blood.
An average human has 2L hemoglobin, has 5-6L of blood, and uses 600L O2 per
day.
Myoglobin vs. hemoglobin: structures - CORRECT ANSWER ✔✔- Myoglobin (Mb)
and the two chains of hemoglobin (Hb) are homologous proteins, meaning they
had a common ancestor, with random mutations over evolutionary time resulting
in key changes. Homologous proteins often have similar sequences, and similar 3-
D structures, as is the case here.
They have similar secondary and tertiary structures, both having about 78% alpha
helix makeup (8 alpha helixes). They both have one heme group, with a non-polar
interior.
However, they differ in their quaternary structure:
Myoglobin has none, while hemoglobin has 2 alpha chains and 2 beta chains
combined into one structure with heme at the center of each, attached to iron.
How does hemoglobin bind oxygen, and what are some competitive inhibitors? -
CORRECT ANSWER ✔✔- Hemoglobin binds O2 reversibly using its heme prosthetic
group, attached to Fe2+.
Other ligand compete favorably with O2, like CO, NO, and H2S.
Pg. 3
, What determines the amount of oxygen bound to hemoglobin (saturation)? -
CORRECT ANSWER ✔✔- The partial pressure of oxygen, or PO2.
Normal arterial O2 pressures, typically around 100 mmHg, give 97% hemoglobin
saturation.
However, when blood travels to tissues, PO2 is much lower than in the lungs,
typically around 20-40mmHg. This cues hemoglobin to release oxygen to the
tissues, leaving it about 50% saturated (2 oxygen molecules have been released).
What fibrous protein makes up spider webs, and why? - CORRECT ANSWER ✔✔-
Spider webs require high tensile strength and low-density (rates of strength to
density exceed that of steel). As a result, the protein fibroin makes up the
majority of spider webs: it is flexible, light, and high-strength. In spider webs, it
combines with the gummy protein sericin to cement it together.
Metabolism (catabolism and anabolism) - CORRECT 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.
Pg. 4
EXAM COMPLETE 550 QUESTIONS WITH
DETAILED VERIFIED ANSWERS (100%
CORRECT ANSWERS) / ALREADY
GRADED A+
What fibrous protein are blood vessels made out of, and why? - CORRECT
ANSWER ✔✔- They are mostly elastin. They require the ability to expand and
contract with each heart beat- they must be extensible but also resilient. So,
elastin is the perfect material.
It is common for tissues requiring flexibility to have a network of elastic fibers
interwoven with collagen (the elastic fibers being 50% elastin by mass).
Elastin Structure - CORRECT ANSWER ✔✔- Alternating hydrophilic and
hydrophobic domains give elastin its key ability to stretch and compress like a
rubber band: the hydrophobic domains are like a plate of spaghetti in the related
state- they are gathered away from water.
Upon being stretched, the molecules uncoil into an extended conformation, but
immediately coil back to a hydrophobic clump once the force is removed! This
combination gives elastin its rubber band-like ability.
Elastin Cross-links - CORRECT ANSWER ✔✔- Lysine cross-links ensure the
molecule returns to its original state after stretching.
Pg. 1
,What fibrous protein makes up skin, and why? - CORRECT ANSWER ✔✔- Skin
requires elasticity, resilience, strength, and protection- so keratin is key, along
with elastin and collagen.
Alpha Keratin (what composes, and its fundamental structure) - CORRECT
ANSWER ✔✔- Composes skin, hair, wool, feathers, nails, claws, quills, horns,
hooves, etc.
Fundamental structure is an alpha helix. Two alpha helixes coil together to give a
two-chain coil, which then bovines with another two-chain coil to give a
protofilament, which then further combine to give a protofibril.
Alpha Keratin Cross links - CORRECT ANSWER ✔✔- Helicies and fibers are cross-
linked by disulfide linkages.
When getting a perm, straight hair is given a chemical treatment that reduces the
disulfide bonds to S-H groups, then the desired style is given, then the S-H bonds
are oxidized back to disulfide bonds, in the desired style, holding it in place.
Silk Fibroin structure - CORRECT ANSWER ✔✔- It has the repeating structure GLY-
ALA-GLY-ALA.
It is an anti-parallel (strong) beta sheet, with amorphous regions surrounding
bulky residues.
Fibrous vs. globular proteins - CORRECT ANSWER ✔✔- Fibrous proteins have a
single major type of secondary structure, while most other proteins are folded
compactly and have a mix of secondary structures.
Pg. 2
,Myoglobin - CORRECT ANSWER ✔✔- The oxygen carrying protein of red muscle.
Hemoglobin - CORRECT ANSWER ✔✔- The oxygen carrying protein of the blood.
An average human has 2L hemoglobin, has 5-6L of blood, and uses 600L O2 per
day.
Myoglobin vs. hemoglobin: structures - CORRECT ANSWER ✔✔- Myoglobin (Mb)
and the two chains of hemoglobin (Hb) are homologous proteins, meaning they
had a common ancestor, with random mutations over evolutionary time resulting
in key changes. Homologous proteins often have similar sequences, and similar 3-
D structures, as is the case here.
They have similar secondary and tertiary structures, both having about 78% alpha
helix makeup (8 alpha helixes). They both have one heme group, with a non-polar
interior.
However, they differ in their quaternary structure:
Myoglobin has none, while hemoglobin has 2 alpha chains and 2 beta chains
combined into one structure with heme at the center of each, attached to iron.
How does hemoglobin bind oxygen, and what are some competitive inhibitors? -
CORRECT ANSWER ✔✔- Hemoglobin binds O2 reversibly using its heme prosthetic
group, attached to Fe2+.
Other ligand compete favorably with O2, like CO, NO, and H2S.
Pg. 3
, What determines the amount of oxygen bound to hemoglobin (saturation)? -
CORRECT ANSWER ✔✔- The partial pressure of oxygen, or PO2.
Normal arterial O2 pressures, typically around 100 mmHg, give 97% hemoglobin
saturation.
However, when blood travels to tissues, PO2 is much lower than in the lungs,
typically around 20-40mmHg. This cues hemoglobin to release oxygen to the
tissues, leaving it about 50% saturated (2 oxygen molecules have been released).
What fibrous protein makes up spider webs, and why? - CORRECT ANSWER ✔✔-
Spider webs require high tensile strength and low-density (rates of strength to
density exceed that of steel). As a result, the protein fibroin makes up the
majority of spider webs: it is flexible, light, and high-strength. In spider webs, it
combines with the gummy protein sericin to cement it together.
Metabolism (catabolism and anabolism) - CORRECT 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.
Pg. 4
