Exam Bank for MCAT Biochemistry- Questions and Answers Solved 100% Latest Version 2024-2025
How many ATPs does oxidation of caprylic acid (C8 saturated fatty acid) produce? - Answers A: Complex
oxidation of this acid yields 61 ATPs.
The activated fatty acyl-CoA proceeds 4 rounds of B-oxidation (because C8) and is converted to 4 acetyl
CoA. ♣ Each acetyl-CoA enters the krebs cycle which produces 1 GTP, 1 FADH2, and 3NADH. From
here, 48 ATPs produced. 2) Complete oxidation of C8 fatty acid hives 3 FADH2 and 3 NADH from B-
oxidation. Also the cleavage of the last 4 carbon compound gives 2 molecules of acetyl-CoA that enter
the Krebs cycle, but neither undergo B oxidation. Thus, in total, we gained 61 ATPs.
Cefixime displays what inhibitive behavior on PBP? - Answers A: Suicide inhibition
According to the passage, cephalosporins bind irreversibly to the active site of PBP. Suicide inhibition
occurs when an enzyme binds the inhibitor (structurally a substrate analogue) and forms an
IRREVERSIBLE complex through a covalent bond.
Steps of signal transduction pathway - Answers 1) Release of appropriate signal molecule "primary
messenger", 2) binding of the primary messenger to its receptor, 3) increase in intracellular
concentration of secondary messengers, resulting in the amplification of the signal, 4)
activation/inhibition of effectors, 5) Termination of pathway (regulated by dissociation of primary
messengers, GTPase activity of G-proteins, and phosphatase)
- Calcium serves as a secondary messenger in many signal transduction pathways and calmodulin is a
regulatory protein that detects changes in calcium ion concentrations
- Secondary messenger is used by all signal transduction pathways. Intracellular agents whose
concentration can be amplified, causing an amplification of the initial signal
Lactose intolerance - Answers Cells use lactose to produce ATP via lactic acid fermentation. The build up
of lactate and lactose in intestine (from lactose intolerance) will cause water to flow out of the cells and
into lumen, causing diarrhea
- High concentration of galactose can lead to: 1) lethargy, 2) liver environment and damage, 3) delayed
mental development
Energy charge - Answers The ratio of ATP to AMP; low energy charge indicates the need of glycolysis and
production of ATP
,Glucose transporters - Answers Glucose molecules are large and polar; they can't simply diffuse across
the membrane. Thus, the cells of our body need "glucose transporters" to uptake glucose from the
blood.
Glut-1: Found in all cells of the body
Glut-2: Typically in liver and pancreas
Glut-3: Dendrites and neurons
Glut-4: Muscle and adipose tissue
Glut-5: Small intestine cells
Pyruvate dehydrogenase complex - Answers - Pyruvate dehydrogenase (E1) catalyzes the redox-
decarboxylation
- Dihydrolipoyl transacetylase (E2) catalyzes the transfer of the acetyl group
- Dihydrolipoyl dehydrogenase (E3) reforms the oxidized version of lipoamides
Pyruvate decarboylation where pyruvate is converted into acetyl-CoA
Glycerol 3-phosphate shuttle - Answers Predominantly used by skeletal muscle cells which allows them
to quickly regenerate NAD+ from NADH (by-product of glycolysis) and synthesize ATP (1.5 ATP per
NADH)
Found in animals, fungi, and plants
Malate-aspartate shuttle - Answers In cardiac muscle cells and liver cells, the malate-aspartate shuttle is
used to transport NADH molecules into the matrix of mitochondria (2.5 ATP per NADH)
It translocates electrons produced during glycolysis across the semipermeable inner membrane of the
mitochondrion for oxidative phosphorylation in *eukaryotes*. These electrons enter the electron
transport chain of the mitochondria via reduction equivalents to generate ATP. The shuttle system is
required because the mitochondrial inner membrane is impermeable to NADH, the primary reducing
equivalent of the electron transport chain. To circumvent this, malate carries the reducing equivalents
across the membrane.
,A particular protein largely lacks both secondary and tertiary structure. Which factor is mainly
responsible for the resting state of this protein? - Answers A: Entropy
Hydrogen bonds, disulfide bonds, and dipole-dipole interactions produce the complex folding patterns in
secondary and tertiary structure. However, if a protein doesn't have these elements of structure, it will
adopt a state where its entropy is maximized.
The rate of actin polymerization in a solution was observed and plotted against the concentration of
actin. What is the critical concentration of actin under these conditions? - Answers A: Concentration
where its polymerization rate is 0
With regard to actin, the critical concentration is the point at which no net
polymerization/depolymerization occurs; this is the concentration where the length of the polymer is
stable
Why does polymerization occur much more rapidly at the (+) end at an actin polymer than at the (-) end
- Answers A: The (+) ends of actin molecules display stronger intermolecular interactions than the (-)
ends
While the rate of polymerization/depolymerization depends on the surrounding actin concentration, the
(+) end grows much more quickly. (+) actin is bound to ATP while (-) actin is bound to ADP. When the (+)
actin polymerizes, ATP is cleaved to become ADP; ADP at (=) end interacts much weakly, promoting
slower polymerization
- At the (-) end of a microtubule, depolymerization is prevented by anchoring of that end to an MTOC
(Microtubule-organizing centers). All microtubules originate from MTOC.
A researcher compares two antibodies that recognize the same antigen, even though they are made by
different animal species. How will these antibodies differ? - Answers A: The antibodies will have
different constant regions
Antibodies of different isotypes (IgA, IgG) differ in their constant regions as they are made by separate
species. The constant region is recognized by other immune systems to further stimulate the response
to a pathogen.
- two antibodies CAN recognize the same antigen
Dyneins, motor proteins that are associated with microtubules, play a vital role in the transport of
cellular components. How can the intracellular movement of dyneins be described?
, I. Dyneins travel toward the center of the cell.
II. Dyneins move toward the minus ends of their associated microtubules.
III. Dyneins are involved in retrograde transport. - Answers A: I, II, and III
A dynein "walks" down its microtubule towards the minus end, a terminal typically oriented towards the
central region of the cell. This act of traveling inward from the cell membrane is known as retrograde
transport
Maxine is researching ways to reduce the activity of an enzyme implicated in a number of diseases. She
is attempting to engineer an antagonist molecule that will competitively inhibit this disease-causing
catalyst. To do so, Maxine should create a molecule that most closely resembles the - Answers A:
Transition state of the enzyme-catalyzed reaction
Because enzymes increase the rate of reaction by reducing activation energy, they have the highest
affinity for (and best stabilizes) the transition states. Therefore, a transition state analogue can be a
potent inhibitor.
What are reasonable estimates of the optimal pH values for pepsin and chymotrypsin? - Answers A: 1.5,
6.5
The stomach is a HIGHLY ACIDIC environment where HCl causes the pH to drop below 2. Any enzymes
that operate here including pepsin must be able to function efficiently in such conditions. In contrast,
chymotrypsin (small intestine) operates within the small intestine where its pH is higher due to the
secretion of bicarbonate ion
After the application of Compound Z, the hemoglobin in a blood sample is only able to transport oxygen
at 50% efficiency. However, studies show that Compound Z does not attach to hemoglobin's oxygen-
binding site. Assuming a direct interaction between Compound Z and hemoglobin, which mechanism is
most likely responsible for this change in O2 transport efficiency? - Answers A: Allosteric inhibition
This question mentions that NO compound Z was found in the ligand-binding site. Inhibition of a
protein's function through attachment to a position other than the active site is termed allosteric
inhibition
How many ATPs does oxidation of caprylic acid (C8 saturated fatty acid) produce? - Answers A: Complex
oxidation of this acid yields 61 ATPs.
The activated fatty acyl-CoA proceeds 4 rounds of B-oxidation (because C8) and is converted to 4 acetyl
CoA. ♣ Each acetyl-CoA enters the krebs cycle which produces 1 GTP, 1 FADH2, and 3NADH. From
here, 48 ATPs produced. 2) Complete oxidation of C8 fatty acid hives 3 FADH2 and 3 NADH from B-
oxidation. Also the cleavage of the last 4 carbon compound gives 2 molecules of acetyl-CoA that enter
the Krebs cycle, but neither undergo B oxidation. Thus, in total, we gained 61 ATPs.
Cefixime displays what inhibitive behavior on PBP? - Answers A: Suicide inhibition
According to the passage, cephalosporins bind irreversibly to the active site of PBP. Suicide inhibition
occurs when an enzyme binds the inhibitor (structurally a substrate analogue) and forms an
IRREVERSIBLE complex through a covalent bond.
Steps of signal transduction pathway - Answers 1) Release of appropriate signal molecule "primary
messenger", 2) binding of the primary messenger to its receptor, 3) increase in intracellular
concentration of secondary messengers, resulting in the amplification of the signal, 4)
activation/inhibition of effectors, 5) Termination of pathway (regulated by dissociation of primary
messengers, GTPase activity of G-proteins, and phosphatase)
- Calcium serves as a secondary messenger in many signal transduction pathways and calmodulin is a
regulatory protein that detects changes in calcium ion concentrations
- Secondary messenger is used by all signal transduction pathways. Intracellular agents whose
concentration can be amplified, causing an amplification of the initial signal
Lactose intolerance - Answers Cells use lactose to produce ATP via lactic acid fermentation. The build up
of lactate and lactose in intestine (from lactose intolerance) will cause water to flow out of the cells and
into lumen, causing diarrhea
- High concentration of galactose can lead to: 1) lethargy, 2) liver environment and damage, 3) delayed
mental development
Energy charge - Answers The ratio of ATP to AMP; low energy charge indicates the need of glycolysis and
production of ATP
,Glucose transporters - Answers Glucose molecules are large and polar; they can't simply diffuse across
the membrane. Thus, the cells of our body need "glucose transporters" to uptake glucose from the
blood.
Glut-1: Found in all cells of the body
Glut-2: Typically in liver and pancreas
Glut-3: Dendrites and neurons
Glut-4: Muscle and adipose tissue
Glut-5: Small intestine cells
Pyruvate dehydrogenase complex - Answers - Pyruvate dehydrogenase (E1) catalyzes the redox-
decarboxylation
- Dihydrolipoyl transacetylase (E2) catalyzes the transfer of the acetyl group
- Dihydrolipoyl dehydrogenase (E3) reforms the oxidized version of lipoamides
Pyruvate decarboylation where pyruvate is converted into acetyl-CoA
Glycerol 3-phosphate shuttle - Answers Predominantly used by skeletal muscle cells which allows them
to quickly regenerate NAD+ from NADH (by-product of glycolysis) and synthesize ATP (1.5 ATP per
NADH)
Found in animals, fungi, and plants
Malate-aspartate shuttle - Answers In cardiac muscle cells and liver cells, the malate-aspartate shuttle is
used to transport NADH molecules into the matrix of mitochondria (2.5 ATP per NADH)
It translocates electrons produced during glycolysis across the semipermeable inner membrane of the
mitochondrion for oxidative phosphorylation in *eukaryotes*. These electrons enter the electron
transport chain of the mitochondria via reduction equivalents to generate ATP. The shuttle system is
required because the mitochondrial inner membrane is impermeable to NADH, the primary reducing
equivalent of the electron transport chain. To circumvent this, malate carries the reducing equivalents
across the membrane.
,A particular protein largely lacks both secondary and tertiary structure. Which factor is mainly
responsible for the resting state of this protein? - Answers A: Entropy
Hydrogen bonds, disulfide bonds, and dipole-dipole interactions produce the complex folding patterns in
secondary and tertiary structure. However, if a protein doesn't have these elements of structure, it will
adopt a state where its entropy is maximized.
The rate of actin polymerization in a solution was observed and plotted against the concentration of
actin. What is the critical concentration of actin under these conditions? - Answers A: Concentration
where its polymerization rate is 0
With regard to actin, the critical concentration is the point at which no net
polymerization/depolymerization occurs; this is the concentration where the length of the polymer is
stable
Why does polymerization occur much more rapidly at the (+) end at an actin polymer than at the (-) end
- Answers A: The (+) ends of actin molecules display stronger intermolecular interactions than the (-)
ends
While the rate of polymerization/depolymerization depends on the surrounding actin concentration, the
(+) end grows much more quickly. (+) actin is bound to ATP while (-) actin is bound to ADP. When the (+)
actin polymerizes, ATP is cleaved to become ADP; ADP at (=) end interacts much weakly, promoting
slower polymerization
- At the (-) end of a microtubule, depolymerization is prevented by anchoring of that end to an MTOC
(Microtubule-organizing centers). All microtubules originate from MTOC.
A researcher compares two antibodies that recognize the same antigen, even though they are made by
different animal species. How will these antibodies differ? - Answers A: The antibodies will have
different constant regions
Antibodies of different isotypes (IgA, IgG) differ in their constant regions as they are made by separate
species. The constant region is recognized by other immune systems to further stimulate the response
to a pathogen.
- two antibodies CAN recognize the same antigen
Dyneins, motor proteins that are associated with microtubules, play a vital role in the transport of
cellular components. How can the intracellular movement of dyneins be described?
, I. Dyneins travel toward the center of the cell.
II. Dyneins move toward the minus ends of their associated microtubules.
III. Dyneins are involved in retrograde transport. - Answers A: I, II, and III
A dynein "walks" down its microtubule towards the minus end, a terminal typically oriented towards the
central region of the cell. This act of traveling inward from the cell membrane is known as retrograde
transport
Maxine is researching ways to reduce the activity of an enzyme implicated in a number of diseases. She
is attempting to engineer an antagonist molecule that will competitively inhibit this disease-causing
catalyst. To do so, Maxine should create a molecule that most closely resembles the - Answers A:
Transition state of the enzyme-catalyzed reaction
Because enzymes increase the rate of reaction by reducing activation energy, they have the highest
affinity for (and best stabilizes) the transition states. Therefore, a transition state analogue can be a
potent inhibitor.
What are reasonable estimates of the optimal pH values for pepsin and chymotrypsin? - Answers A: 1.5,
6.5
The stomach is a HIGHLY ACIDIC environment where HCl causes the pH to drop below 2. Any enzymes
that operate here including pepsin must be able to function efficiently in such conditions. In contrast,
chymotrypsin (small intestine) operates within the small intestine where its pH is higher due to the
secretion of bicarbonate ion
After the application of Compound Z, the hemoglobin in a blood sample is only able to transport oxygen
at 50% efficiency. However, studies show that Compound Z does not attach to hemoglobin's oxygen-
binding site. Assuming a direct interaction between Compound Z and hemoglobin, which mechanism is
most likely responsible for this change in O2 transport efficiency? - Answers A: Allosteric inhibition
This question mentions that NO compound Z was found in the ligand-binding site. Inhibition of a
protein's function through attachment to a position other than the active site is termed allosteric
inhibition
