Biomedical Science I Exam II

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Biomedical Science I Exam II - Quiz

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Questions and Answers
  • 1. 

    Which of the following statements is (are) correct(s) about enzymes? Select all that apply.

    • A.

      As chemical reactions undergo, entropy (disorder) will increase

    • B.

      Enzymes increase the rate of the reaction by increasing the activation energy (Ea)

    • C.

      A reaction with a negative ΔG is said to be unfavorable

    • D.

      Enzymes are specific catalysts that remain unchanged following a reaction

    • E.

      Polymorphism among individuals can change the activity of enzymes which will effect the metabolism of the drug

    Correct Answer(s)
    A. As chemical reactions undergo, entropy (disorder) will increase
    D. Enzymes are specific catalysts that remain unchanged following a reaction
    E. Polymorphism among individuals can change the activity of enzymes which will effect the metabolism of the drug
    Explanation
    1. As chemical reactions undergo, entropy (disorder) will increase: This statement is correct because as reactions occur, molecules become more disordered, leading to an increase in entropy.
    2. Enzymes are specific catalysts that remain unchanged following a reaction: This statement is correct because enzymes are not consumed or altered during a reaction, allowing them to be reused.
    3. Polymorphism among individuals can change the activity of enzymes which will affect the metabolism of the drug: This statement is correct because genetic variations can result in different enzyme forms or levels, leading to variations in drug metabolism.

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  • 2. 

    In a Gs transduction signaling pathway, activation of the effector leads to the activation of?

    • A.

      G-alpha subunit

    • B.

      CAMP

    • C.

      Protein Kinase A (PKA)

    • D.

      Adenylyl Cyclase

    • E.

      CREB

    Correct Answer
    B. CAMP
    Explanation
    In a Gs transduction signaling pathway, the activation of the effector leads to the activation of cAMP. This is because the Gs protein acts as a molecular switch, activating adenylyl cyclase when it is bound to GTP. Adenylyl cyclase then catalyzes the conversion of ATP to cAMP. cAMP then acts as a second messenger, activating protein kinase A (PKA) which can phosphorylate and activate downstream target proteins such as CREB. Therefore, cAMP is a key mediator in transmitting signals from the Gs transduction pathway to activate various cellular processes.

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  • 3. 

    Which of the following is correct about Gs Signal Transduction Pathway? Select all that apply

    • A.

      G-protein is monomeric and possesses GTPase activity

    • B.

      The activation of PKA leads to the amplification of cAMP

    • C.

      Requires the alpha-subunit to activate Adenylyl Cyclase

    • D.

      The G-protein requires the binding of GDP for activation

    • E.

      Can lead to the phosphorylation of CREB

    Correct Answer(s)
    B. The activation of PKA leads to the amplification of cAMP
    C. Requires the alpha-subunit to activate Adenylyl Cyclase
    E. Can lead to the phosphorylation of CREB
    Explanation
    The activation of PKA leads to the amplification of cAMP because PKA phosphorylates and activates adenylyl cyclase, which in turn catalyzes the conversion of ATP to cAMP, leading to an increase in cAMP levels. Requires the alpha-subunit to activate Adenylyl Cyclase because the alpha-subunit of the G-protein directly interacts with and activates adenylyl cyclase. Can lead to the phosphorylation of CREB because cAMP activates PKA, which then phosphorylates CREB, leading to its activation.

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  • 4. 

    Which of the following about enzyme kinetics is false?

    • A.

      In competitive inhibition, there is an increase in Km and no change in Vmax

    • B.

      In uncompetitive inhibition, there is a decrease in Km and Vmax

    • C.

      In non-competitive inhibition, there is a decrease in Km and Vmax

    • D.

      An increase in Km correlates to a decrease in the affinity of the enzyme to the substrate

    Correct Answer
    C. In non-competitive inhibition, there is a decrease in Km and Vmax
    Explanation
    In non-competitive inhibition, there is no change in Km, but there is a decrease in Vmax. This means that the affinity of the enzyme to the substrate remains the same, but the maximum rate of reaction is reduced.

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  • 5. 

    Which of the following sequence of events is correct for Gs Signal Transduction Pathway?

    • A.

      Ligand --> Receptor --> G-protein --> PKA --> cAMP --> Adenylyl Cyclase

    • B.

      Ligand --> Receptor --> G-protein --> Adenylyl Cyclase --> PKA --> cAMP

    • C.

      Ligand --> G-protein --> Receptor --> PKA --> cAMP --> Adenylyl Cyclase

    • D.

      Ligand --> Receptor --> G-protein --> Adenylyl Cyclase --> cAMP --> PKA

    Correct Answer
    D. Ligand --> Receptor --> G-protein --> Adenylyl Cyclase --> cAMP --> PKA
    Explanation
    The correct sequence of events for the Gs Signal Transduction Pathway is as follows: Ligand binds to the receptor, which activates the G-protein. The activated G-protein then stimulates Adenylyl Cyclase, leading to the production of cAMP. Finally, cAMP activates PKA. This sequence of events is the correct order in which the signaling molecules and enzymes are activated and interact with each other in the Gs Signal Transduction Pathway.

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  • 6. 

    Which of the following statements is correct about enzyme kinetics? Select all that apply

    • A.

      In competitive inhibition, the inhibitor competes with the substrate for the active site

    • B.

      Irreversible inhibition includes covalent modifications

    • C.

      Low Km = Low [S] = High Affinity

    • D.

      Vmax is the rate of the reaction when the enzyme has low substrate concentration

    Correct Answer(s)
    A. In competitive inhibition, the inhibitor competes with the substrate for the active site
    B. Irreversible inhibition includes covalent modifications
    C. Low Km = Low [S] = High Affinity
    Explanation
    In competitive inhibition, the inhibitor competes with the substrate for the active site, meaning that both the inhibitor and substrate cannot bind to the enzyme simultaneously. Irreversible inhibition involves covalent modifications, where the inhibitor forms a covalent bond with the enzyme, rendering it permanently inactive. Low Km indicates low substrate concentration required for the enzyme to reach half of its maximum velocity, indicating high affinity between the enzyme and substrate.

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  • 7. 

    Which of the following statements is correct about types of enzymes? Select all that apply

    • A.

      Kinases attach phosphate groups to molecules

    • B.

      Hydrolases cleave water as part of a reaction

    • C.

      ATPases hydrolyze ADP --> ATP as part of a reaction

    • D.

      Phosphatases remove phosphate groups off molecules

    • E.

      Synthases form a large molecule from two small molecules

    Correct Answer(s)
    A. Kinases attach phosphate groups to molecules
    B. Hydrolases cleave water as part of a reaction
    D. Phosphatases remove phosphate groups off molecules
    E. Synthases form a large molecule from two small molecules
    Explanation
    Kinases attach phosphate groups to molecules. This statement is correct because kinases are enzymes that catalyze the transfer of a phosphate group from ATP to a molecule, often a protein or a small molecule.

    Hydrolases cleave water as part of a reaction. This statement is correct because hydrolases are enzymes that catalyze the cleavage of a molecule by adding water to it, resulting in the breaking of chemical bonds.

    ATPases hydrolyze ADP --> ATP as part of a reaction. This statement is incorrect because ATPases are enzymes that hydrolyze ATP to ADP and inorganic phosphate (Pi) as part of a reaction.

    Phosphatases remove phosphate groups off molecules. This statement is correct because phosphatases are enzymes that catalyze the removal of phosphate groups from molecules, often proteins or nucleotides.

    Synthases form a large molecule from two small molecules. This statement is correct because synthases are enzymes that catalyze the synthesis of a larger molecule from two smaller molecules, often through the formation of a new bond.

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  • 8. 

    Which of the following statements is false about Receptors and Signal Transduction? 

    • A.

      Gap junctions, a type of contact-dependent signaling is the fastest form of signaling

    • B.

      The secretion of the hormone oxytocin from the Posterior Pituitary Gland causes uterine contractions during labor. This signaling occurs quickly and has a short effect.

    • C.

      Down-regulation of receptors is likely to occur due to high levels of chemical messenger

    • D.

      Amplification of secondary messengers allows for regulation (e.g. drugs)

    • E.

      Calcium and cAMP are secondary messengers of Gs Signal Transduction Pathway

    Correct Answer
    B. The secretion of the hormone oxytocin from the Posterior Pituitary Gland causes uterine contractions during labor. This signaling occurs quickly and has a short effect.
    Explanation
    The statement is false because the secretion of oxytocin from the Posterior Pituitary Gland does not cause uterine contractions quickly. Instead, it is a slow process that occurs gradually over time. Additionally, the effects of oxytocin on uterine contractions are long-lasting, not short-lived.

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  • 9. 

    Which of the following statements are correct about MAPK Signal Transduction? Select all that apply

    • A.

      Epidermal Growth Factor is the first messenger

    • B.

      Once the ligand binds to the receptors, the receptors dimerize which allows for phosphorylation to occur

    • C.

      Ras is heteromeric G protein which activates a kinase that phosphorylates MAPK

    • D.

      Ras requires extrinsic GTPase activity; in which Guanine Nucleotide Exchange Factors (GEF) converts GTP --> GDP and GTPase activating Proteins (GAP) converts GDP --> GTP.

    • E.

      Ras is activated by the binding of GTP

    Correct Answer(s)
    A. Epidermal Growth Factor is the first messenger
    B. Once the ligand binds to the receptors, the receptors dimerize which allows for phosphorylation to occur
    E. Ras is activated by the binding of GTP
    Explanation
    Epidermal Growth Factor (EGF) acts as the first messenger in MAPK Signal Transduction, initiating the signaling cascade. Once the ligand (EGF) binds to the receptors, they dimerize, bringing them closer together. This dimerization enables the receptors to phosphorylate each other, leading to the activation of downstream signaling molecules. Ras, a heteromeric G protein, is activated by the binding of GTP. Once activated, Ras activates a kinase that phosphorylates MAPK, thereby transmitting the signal further downstream. The statement about Ras requiring extrinsic GTPase activity, involving Guanine Nucleotide Exchange Factors (GEF) and GTPase activating Proteins (GAP), is not mentioned in the given answer.

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  • 10. 

    Which of the following statements are correct about GPCR's? Select all that apply

    • A.

      Cholera toxin causes rapid production of Gs signaling which causes diarrhea and dehydration

    • B.

      Phosphodiesterases (PDEs) are a method of self-regulation which stops signaling by converting cAMP into 5'-AMP, the inactivated form.

    • C.

      PKA is activated by the binding of 4 cAMP molecules to its regulatory subunit

    • D.

      Pertussis causes decreased production of a physiological response by inhibiting Gi signaling

    • E.

      Phosphorylation of GPCR by GRKs prevents arrestin from inhibiting the interaction between the receptor and the G-protein

    Correct Answer(s)
    A. Cholera toxin causes rapid production of Gs signaling which causes diarrhea and dehydration
    B. Phosphodiesterases (PDEs) are a method of self-regulation which stops signaling by converting cAMP into 5'-AMP, the inactivated form.
    C. PKA is activated by the binding of 4 cAMP molecules to its regulatory subunit
    Explanation
    Cholera toxin causes rapid production of Gs signaling which leads to diarrhea and dehydration. Phosphodiesterases (PDEs) regulate signaling by converting cAMP into 5'-AMP, the inactive form. PKA is activated when 4 cAMP molecules bind to its regulatory subunit.

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  • 11. 

    Which of the following statement(s) are correct about SLC proteins? Select all that apply

    • A.

      SLCs are involved in solute influx

    • B.

      SLCs do not directly consume ATP in the movement of solute

    • C.

      Few SLCs are present in tissues that participate in environmental exchange.

    • D.

      GLUT1 is an example of an SLC protein that transports glucose out of the cell.

    • E.

      SLC proteins can use facilitated diffusion or secondary active transport

    Correct Answer(s)
    A. SLCs are involved in solute influx
    B. SLCs do not directly consume ATP in the movement of solute
    E. SLC proteins can use facilitated diffusion or secondary active transport
    Explanation
    SLCs are a group of proteins that are involved in the movement of solutes across cell membranes. They are responsible for solute influx, meaning they transport solutes into the cell. Unlike some other transport proteins, SLCs do not directly consume ATP in the movement of solute. Instead, they can use facilitated diffusion or secondary active transport, which do not require ATP. Additionally, some SLCs are found in tissues that participate in environmental exchange, allowing for the movement of solutes between the organism and its surroundings. GLUT1 is an example of an SLC protein that transports glucose out of the cell.

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  • 12. 

    Which of the following statements is false about channels? 

    • A.

      Utilizes passive transport in which the solute flows down the concentration gradient

    • B.

      Channels bind more specifically to the solute and transport the solute faster than transporters

    • C.

      Energy is not required for the movement of solutes

    • D.

      An example of a leak channel are aquaporins

    Correct Answer
    B. Channels bind more specifically to the solute and transport the solute faster than transporters
  • 13. 

    Which of the following statement(s) are correct of Aquaporins? Select all that apply

    • A.

      Conducts the transportation of water via leak channels by simple diffusion

    • B.

      Aquaporins in the kidney are controlled by Antidiuretic Hormone (ADH); in which high ADH secretion would dilute the urine and concentrate the blood

    • C.

      Ions are unable to pass through aquaporins due to a narrow pore which hydrated ions are too big to fit in

    • D.

      A mutation of AQP2 (aquaporins in the kidneys) can result in excess reabsorption of water, thus resulting in dilute urine

    • E.

      Molecules pass through the channels by moving down their concentration gradient

    Correct Answer(s)
    C. Ions are unable to pass through aquaporins due to a narrow pore which hydrated ions are too big to fit in
    E. Molecules pass through the channels by moving down their concentration gradient
    Explanation
    Aquaporins are protein channels that facilitate the transport of water molecules across cell membranes. They do not allow the passage of ions due to their narrow pore size, which hydrated ions are too large to fit into. Molecules, including water, pass through aquaporin channels by moving down their concentration gradient. This means that they move from an area of higher concentration to an area of lower concentration. Therefore, the correct statements are that ions are unable to pass through aquaporins due to a narrow pore, and molecules pass through the channels by moving down their concentration gradient.

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  • 14. 

    Which of the following statements are correct about Transporters? Select all that apply

    • A.

      The Na+/K+ Pump is an antiport which pumps 3 Na+ in and 2 K+ out to restore membrane potential by primary active transport

    • B.

      SGLT2 transports glucose against its concentration gradient by coupling it to the movement of Na+ down its concentration gradient

    • C.

      ABC transporters utilize primary active transport to transport solutes into cells

    • D.

      SLCO1B1 transports solutes via a uniporter by facilitated diffusion

    • E.

      The Na+-Amino Acid transporter utilizes a symporter

    Correct Answer(s)
    B. SGLT2 transports glucose against its concentration gradient by coupling it to the movement of Na+ down its concentration gradient
    D. SLCO1B1 transports solutes via a uniporter by facilitated diffusion
    E. The Na+-Amino Acid transporter utilizes a symporter
    Explanation
    The Na+/K+ Pump is an antiport which pumps 3 Na+ in and 2 K+ out to restore membrane potential by primary active transport: This statement is incorrect. The Na+/K+ pump is an antiporter that pumps 3 Na+ out of the cell and 2 K+ into the cell, not the other way around.

    SGLT2 transports glucose against its concentration gradient by coupling it to the movement of Na+ down its concentration gradient: This statement is correct. SGLT2 is a symporter that transports glucose into the cell against its concentration gradient by coupling it to the movement of Na+ down its concentration gradient.

    ABC transporters utilize primary active transport to transport solutes into cells: This statement is incorrect. ABC transporters utilize primary active transport to transport solutes out of cells, not into cells.

    SLCO1B1 transports solutes via a uniporter by facilitated diffusion: This statement is correct. SLCO1B1 is a uniporter that transports solutes into the cell by facilitated diffusion.

    The Na+-Amino Acid transporter utilizes a symporter: This statement is correct. The Na+-Amino Acid transporter is a symporter that transports amino acids into the cell by coupling their movement to the movement of Na+ into the cell.

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  • 15. 

    The receptors of intracellular signaling are located where in the cell? Select all that apply

    • A.

      Plasma Membrane

    • B.

      Cytosol

    • C.

      Nucleus

    • D.

      Endoplasmic Reticulum

    • E.

      Mitochondria

    Correct Answer(s)
    B. Cytosol
    C. Nucleus
    Explanation
    The receptors of intracellular signaling can be located in the cytosol and nucleus of the cell. This means that they are present within the fluid portion of the cell (cytosol) as well as inside the nucleus, where the genetic material is housed. These receptors are responsible for receiving signals and transmitting them to the appropriate cellular machinery to initiate a response. The plasma membrane, endoplasmic reticulum, and mitochondria are not locations where intracellular signaling receptors are typically found.

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  • 16. 

    Which of the following is false about enzymes?

    • A.

      2nd law of thermodynamics suggests that systems will move towards more disorder

    • B.

      Substrate alignment is a type of reaction which depends on orientation of enzyme and substrate

    • C.

      Uncompetitive inhibitors bind to the Enzyme-Substrate Complex which decreases Km and Vmax

    • D.

      Enzymes are catalysts which lower the activation energy of a reaction

    • E.

      Isomerases catalyze polymerization reactions

    Correct Answer
    E. Isomerases catalyze polymerization reactions
  • 17. 

    Which of the following are correct about SGLT2 Transporters? Select all that apply

    • A.

      Requires the input of energy eventually

    • B.

      SGLT2 is a symporter which transports Glucose and Sodium

    • C.

      Inhibition of SGLT2 would lead to excess blood glucose

    • D.

      Located in the convoluted proximal tubule of the kidneys

    • E.

      Inhibition of SGLT2 is used as treatment of Type I Diabetes Mellitus

    Correct Answer(s)
    A. Requires the input of energy eventually
    B. SGLT2 is a symporter which transports Glucose and Sodium
    D. Located in the convoluted proximal tubule of the kidneys
    Explanation
    SGLT2 transporters require the input of energy eventually because they actively transport glucose and sodium against their concentration gradients. They use the energy from the sodium ion gradient created by Na+/K+ ATPase to drive the transport. SGLT2 is a symporter that transports both glucose and sodium together, meaning they are co-transported across the cell membrane. These transporters are located in the convoluted proximal tubule of the kidneys, where they reabsorb glucose and sodium from the filtrate back into the bloodstream. Inhibition of SGLT2 would lead to excess blood glucose because it prevents the reabsorption of glucose, causing it to be excreted in the urine. However, inhibition of SGLT2 is not used as a treatment for Type I Diabetes Mellitus.

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  • 18. 

    Which of the following are correct of ABC transporters? Select all that apply

    • A.

      ABC proteins possess an Beta-sheet domain which binds ATP

    • B.

      ABCB1 can efflux substrates such as hydrophilic drugs

    • C.

      A mutation resulting of gain of function of P-gp can lead to reduced drug levels in tissue

    • D.

      Requires secondary active transport

    • E.

      Efflux solutes from kidney cells into the blood

    Correct Answer(s)
    C. A mutation resulting of gain of function of P-gp can lead to reduced drug levels in tissue
    E. Efflux solutes from kidney cells into the blood
    Explanation
    ABC transporters are a family of proteins that possess a Beta-sheet domain which binds ATP. They are involved in the efflux of substrates, such as hydrophilic drugs, and can transport solutes from kidney cells into the blood. Additionally, a mutation resulting in a gain of function of P-gp, which is a type of ABC transporter, can lead to reduced drug levels in tissue. These statements accurately describe the characteristics and functions of ABC transporters.

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  • 19. 

    Which of the following are correct of Enzyme-Linked Receptor Signaling? Select all that apply

    • A.

      Receptor dimerization provides access for kinases to autophosphorylate

    • B.

      Ras is a monomeric G protein which require extrinsic enzymes to activate it

    • C.

      Guanine Nucleotide Exchange Factors (GEF) converts GTP --> GDP

    • D.

      Most enzyme-linked receptors are tyrosine kinase receptors

    • E.

      Epidermal Growth Factor binds to eventually activate MAPK

    Correct Answer(s)
    A. Receptor dimerization provides access for kinases to autophosphorylate
    B. Ras is a monomeric G protein which require extrinsic enzymes to activate it
    D. Most enzyme-linked receptors are tyrosine kinase receptors
    E. Epidermal Growth Factor binds to eventually activate MAPK
    Explanation
    Enzyme-linked receptor signaling involves the activation of receptor tyrosine kinases through dimerization, which allows the kinases to phosphorylate themselves (autophosphorylation). Ras is indeed a monomeric G protein that requires extrinsic enzymes (Guanine Nucleotide Exchange Factors) to activate it. Epidermal Growth Factor (EGF) binds to its receptor, leading to the activation of the MAPK signaling pathway. Lastly, most enzyme-linked receptors are indeed tyrosine kinase receptors, which phosphorylate tyrosine residues in their substrates.

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  • 20. 

    A patient has been prescribed Diltiazem, a Calcium Channel Blocker. Diltiazem is metabolized by CYP3A4. After collecting the patients medication history, you realize he has been treated for a respiratory tract infection with erythromycin. Erythromycin is an inhibitor of CYP3A4. Which of the following statements depicts the effect and plan of action?

    • A.

      More drug would be metabolized; increase dose

    • B.

      No effect on Diltiazem

    • C.

      Less drug would be metabolized; increase dose

    • D.

      Less drug would be metabolized; reduce dose

    • E.

      More drug would be metabolized; reduce dose

    Correct Answer
    D. Less drug would be metabolized; reduce dose
    Explanation
    Erythromycin is known to inhibit the enzyme CYP3A4, which is responsible for metabolizing Diltiazem. As a result, the presence of erythromycin would lead to a decrease in the metabolism of Diltiazem. This means that less of the drug would be broken down and eliminated from the body, resulting in higher levels of Diltiazem in the bloodstream. To avoid potential side effects or toxicity from elevated levels of Diltiazem, the appropriate plan of action would be to reduce the dose of Diltiazem. This adjustment would help maintain therapeutic levels of the medication without risking adverse effects.

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  • 21. 

    Which of the following statements are correct about drug metabolism? Select all that apply

    • A.

      CYP2E1 metabolizes 25-30% of all used medications

    • B.

      N-acetyltransferases are responsible for phase I of biotransformation in which the transfer of acetyl groups aids in the metabolism of drugs

    • C.

      CYP3A4 is found in the liver and small intestine and metabolizes about 50% of drugs, endogenous and exogenous compounds

    • D.

      Polymorphism of NAT-2 can results in increased cancer

    • E.

      NAT-1 and NAT-2 are found in almost all tissues

    Correct Answer(s)
    C. CYP3A4 is found in the liver and small intestine and metabolizes about 50% of drugs, endogenous and exogenous compounds
    D. Polymorphism of NAT-2 can results in increased cancer
    Explanation
    CYP3A4 is an enzyme that is present in both the liver and small intestine, and it is responsible for metabolizing approximately 50% of drugs, as well as endogenous and exogenous compounds. Polymorphism of NAT-2 can lead to an increased risk of cancer.

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  • 22. 

    Which of the following statements are correct of the K+ Leak Channel? Select all that apply

    • A.

      The presence of negatively-charge amino acids on the entrance of the pore restricts the entrance of anions but not cations

    • B.

      Na+ can enter the pore but can't move through the selectivity filter due to the presence of carbonyl oxygens in the selectivity filter in which can't fully bind to

    • C.

      The dehydration of K+ ions allows for entry into the selectivity filter

    • D.

      The vestibule is located in the hydrophobic pore where it shortens the distance travelled by the ion

    • E.

      The inner and outer helices provide stabilization to the channel by interacting with lipids in the membrane

    Correct Answer(s)
    A. The presence of negatively-charge amino acids on the entrance of the pore restricts the entrance of anions but not cations
    B. Na+ can enter the pore but can't move through the selectivity filter due to the presence of carbonyl oxygens in the selectivity filter in which can't fully bind to
    C. The dehydration of K+ ions allows for entry into the selectivity filter
    E. The inner and outer helices provide stabilization to the channel by interacting with lipids in the membrane
    Explanation
    The presence of negatively-charged amino acids on the entrance of the pore restricts the entrance of anions but not cations. Na+ can enter the pore but can't move through the selectivity filter due to the presence of carbonyl oxygens in the selectivity filter which can't fully bind to. The dehydration of K+ ions allows for entry into the selectivity filter. The inner and outer helices provide stabilization to the channel by interacting with lipids in the membrane.

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  • 23. 

    Which of the following statements of NAT-2 is false?

    • A.

      Cytosolic enzyme mainly found in the liver, small intestine, and colon

    • B.

      A slow acetylator is more likely to cause drug toxicity

    • C.

      A rapid acetylator is more likely to cause drug toxicity

    • D.

      Functions in the activation and deactivation of drugs

    • E.

      Involved in Phase II of biotransformation

    Correct Answer
    C. A rapid acetylator is more likely to cause drug toxicity
    Explanation
    A rapid acetylator is less likely to cause drug toxicity because this type of acetylator metabolizes drugs more quickly, leading to a faster elimination of the drug from the body. This reduces the chances of drug accumulation and toxicity.

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  • 24. 

    Which of the following statements are correct of Signal Transduction Pathways? Select all that apply

    • A.

      A partial agonist competes with the agonist for the binding site

    • B.

      An effector for the Gs Signal Transduction Pathway is G-alpha subunit

    • C.

      Calcium and IP3 are the only secondary messengers for the Gq Signal Transduction Pathway

    • D.

      Densensitization can occur via receptor sequesteration, down-regulation, and inactivation when a receptor is constantly exposed to ligands

    • E.

      Glucocorticoid and Thyroid Hormone receptors are located in the nucleus

    Correct Answer(s)
    A. A partial agonist competes with the agonist for the binding site
    D. Densensitization can occur via receptor sequesteration, down-regulation, and inactivation when a receptor is constantly exposed to ligands
    Explanation
    A partial agonist competes with the agonist for the binding site. This means that when both the agonist and the partial agonist are present, they will both try to bind to the same receptor site, leading to a competition for binding.

    Densensitization can occur via receptor sequesteration, down-regulation, and inactivation when a receptor is constantly exposed to ligands. This means that when a receptor is constantly exposed to ligands, it can become desensitized or less responsive. This can happen through various mechanisms such as sequestering the receptor away from the cell surface, reducing the number of receptors through down-regulation, or inactivating the receptor.

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  • 25. 

    Which of the following statements are correct of enzyme and enzyme kinetics? Select all that apply

    • A.

      Negative ΔG reactions are unfavorable, thus coupling them to favorable positive ΔG reactions is can allow the reaction to proceed

    • B.

      Bond distortion is a strategic method used by enzymes in which the substrate's electrons are rearranged, creating opposite charges to favor the reaction

    • C.

      An enzymes functional ability is dependent on temperature and pH

    • D.

      CYP450 enzymes are located in the liver in which they catalyze oxidative reactions as part of phase I of biotransformation

    • E.

      Vmax is dependent on the rate at which the product dissociates from the enzyme

    Correct Answer(s)
    C. An enzymes functional ability is dependent on temperature and pH
    D. CYP450 enzymes are located in the liver in which they catalyze oxidative reactions as part of phase I of biotransformation
    E. Vmax is dependent on the rate at which the product dissociates from the enzyme
    Explanation
    Enzymes function optimally within a specific range of temperature and pH. Any deviation from this range can denature the enzyme and affect its functional ability. CYP450 enzymes are primarily found in the liver and are responsible for catalyzing oxidative reactions during phase I of biotransformation. Vmax, or maximum velocity, is the rate at which the enzyme is saturated with substrate. It is dependent on the rate at which the product dissociates from the enzyme.

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  • 26. 

    Which of the following statements are correct about transporters and channels? Select all that apply

    • A.

      An example of a ligand-gated channel is acetylcholine receptors found in neuromuscular junctions

    • B.

      For voltage-gated channels, the inside of the cell must become more negative for the channel to open

    • C.

      For Mechanical-gated channels, distortion of the cell causes the channel to open

    • D.

      Uniporters facilitate the transport of specific solutes by undergoing a conformation change which requires energy

    • E.

      Antiports transport the substrate across the membranes down their concentration gradient

    Correct Answer(s)
    A. An example of a ligand-gated channel is acetylcholine receptors found in neuromuscular junctions
    C. For Mechanical-gated channels, distortion of the cell causes the channel to open
    Explanation
    An example of a ligand-gated channel is acetylcholine receptors found in neuromuscular junctions. This is correct because ligand-gated channels open or close in response to the binding of a specific molecule (ligand) such as acetylcholine.

    For Mechanical-gated channels, distortion of the cell causes the channel to open. This is correct because mechanical-gated channels open or close in response to physical forces or mechanical distortion of the cell membrane.

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  • 27. 

    Which of the following statements about transporters and channels are correct? Select all that apply

    • A.

      A mutation in SLCO1B1 reduces the metabolism of cholesterol lowering drugs thus decreasing their efficacy and increases levels in the blood which can lead to muscle disease.

    • B.

      In a resting cell, there is more Na+ outside the cell and more K+ inside the cell

    • C.

      A peripheral protein crosses the span of the lipid bilayer

    • D.

      Facilitated diffusion does not require energy as it moves molecules down their concentration gradient

    • E.

      SLCO1B1 are found in the kidneys and are dependent on membrane potential and energy

    Correct Answer(s)
    A. A mutation in SLCO1B1 reduces the metabolism of cholesterol lowering drugs thus decreasing their efficacy and increases levels in the blood which can lead to muscle disease.
    B. In a resting cell, there is more Na+ outside the cell and more K+ inside the cell
    D. Facilitated diffusion does not require energy as it moves molecules down their concentration gradient
    Explanation
    A mutation in SLCO1B1 reduces the metabolism of cholesterol lowering drugs, leading to decreased efficacy and increased levels in the blood. This can potentially lead to muscle disease. In a resting cell, there is a higher concentration of Na+ outside the cell and a higher concentration of K+ inside the cell. Facilitated diffusion is a passive process that does not require energy and moves molecules down their concentration gradient.

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  • 28. 

    Which of the following statements is false of enzyme kinetics?

    • A.

      To overcome competitive inhibition, excess substrate is added, which decreases Km

    • B.

      In non-competitive inhibition, there is no competition for the active site, thus Km does not change

    • C.

      A type of irreversible inhibition is disulfide bonds which can bind permanently to heavy metals

    • D.

      The Michaelis-Menten Diagram depicts the relationship between velocity and concentration

    Correct Answer
    A. To overcome competitive inhibition, excess substrate is added, which decreases Km
    Explanation
    Competitive inhibition occurs when a molecule similar to the substrate competes for the active site of the enzyme. To overcome competitive inhibition, excess substrate is added, which increases the chances of the substrate binding to the active site instead of the inhibitor. This increases the Km value, which represents the substrate concentration at which the reaction rate is half of the maximum velocity. Therefore, the given statement is false as excess substrate addition increases Km, rather than decreasing it.

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