BIO-CHEMISTRY FINAL EXAM 140 QUESTIONS AND DETAILED ANSWERS 2024-
2025 LATEST UPDATE ALREADY GRADED A+
The type of membrane transport that uses ion gradients as the energy source is:
A) facilitated diffusion
B) passive transport.
C) primary active transport.
D) secondary active transport.
E) simple diffusion. - answer-D) secondary active transport.
An electrogenic Na+ transporter:
A) catalyzes facilitated diffusion of Na+ from a region of high Na+ concentration to one of lower Na+
concentration.
B) must catalyze an electron transfer (oxidation-reduction) reaction simultaneously with Na+
transport.
C) must transport both Na+ and a counterion (Cl-, for example).
D) transports Na+ against its concentration gradient.
E) transports Na+ without concurrent transport of any other charged species. - answer-E) transports Na+
without concurrent transport of any other charged species.
Movement of water across membranes is facilitated by proteins called:
A) annexins.
B) aquaporins.
C) hydropermeases.
D) selectins.
E) transportins. - answer-B) aquaporins.
The specificity of the potassium channel for K+ over Na+ is mainly the result of the:
A) differential interaction with the selectivity filter protein.
B) hydrophobicity of the channel.
,C) phospholipid composition of the channel.
D) presence of carbohydrates in the channel.
E) presence of cholesterol in the channel. - answer-A) differential interaction with the selectivity filter
protein.
A ligand-gated ion channel (such as the nicotinic acetylcholine receptor) is:
A) a charged lipid in the membrane bilayer that allows ions to pass through.
B) a membrane protein that permits a ligand to pass through the membrane only when opened by the
appropriate ion.
C) a membrane protein that permits an ion to pass through the membrane only when opened by the
appropriate ligand.
D) a molecule that binds to the membrane thereby allowing ions to pass through.
E) always requires a second ligand to close the channel once it is opened. - answer-C) a membrane
protein that permits an ion to pass through the membrane only when opened by the appropriate ligand.
Which of the following is not involved in the specificity of signal transduction?
A) Interactions between receptor and signal molecules
B) Location of receptor molecules
C) Structure of receptor molecules
D) Structure of signal molecules
E) Transmembrane transport of signal molecules by receptor molecules - answer-E) Transmembrane
transport of signal molecules by receptor molecules
Scatchard analysis can provide information on:
A) enzyme cascades.
B) enzyme mechanisms.
C) gated ion channels.
D) protein phosphorylation.
E) receptor-ligand interactions. - answer-E) receptor-ligand interactions.
,The force that drives an ion through a membrane channel depends upon:
A) the charge on the membrane.
B) the difference in electrical potential across the membrane.
C) the size of the channel.
D) the size of the ion.
E) the size of the membrane. - answer-B) the difference in electrical potential across the membrane.
The ion channel that opens in response to acetylcholine is an example of a ____________ signal
transduction system.
A) G protein
B) ligand-gated
C) receptor-enzyme
D) serpentine receptor
E) voltage-gated - answer-B) ligand-gated
The effects of acetylcholine on the postsynaptic ion channel are mainly due to:
A) cyclic nucleotide synthesis.
B) protein cleavage (proteolysis).
C) protein conformational changes.
D) protein phosphorylation.
E) protein synthesis. - answer-C) protein conformational changes.
Which of the following statements concerning signal transduction by the insulin receptor is not correct?
A) Activation of the receptor protein kinase activity results in the activation of additional protein
kinases.
B) Binding of insulin to the receptor activates a protein kinase.
C) Binding of insulin to the receptor results in a change in its quaternary structure.
D) The receptor protein kinase activity is specific for tyrosine residues on the substrate proteins.
, E) The substrates of the receptor protein kinase activity are mainly proteins that regulate transcription. -
answer-E) The substrates of the receptor protein kinase activity are mainly proteins that regulate
transcription.
Which of the following statements concerning receptor enzymes is correct?
A) They are not usually membrane-associated proteins.
B) They contain an enzyme activity that acts upon a cytosolic substrate.
C) They contain an enzyme activity that acts upon the extracellular ligand.
D) They have a ligand-binding site on the cytosolic side of the membrane.
E) They have an active site on the extracellular side of the membrane. - answer-B) They contain an
enzyme activity that acts upon a cytosolic substrate.
Guanyl cyclase receptor enzymes:
A) are all membrane-spanning proteins.
B) are examples of ligand-gated ion channels.
C) catalyze synthesis of a phosphate ester.
D) catalyze synthesis of a phosphoric acid anhydride.
E) require hydrolysis of ATP in addition to GTP. - answer-C) catalyze synthesis of a phosphate ester.
Serpentine receptors:
A) are examples of G (GTP-binding) regulatory proteins.
B) are mainly involved in the regulation of ion transport.
C) are present in prokaryotic cells but not in eukaryotic cells.
D) are present in the nucleus and affect gene expression.
E) have multiple membrane-spanning helical domains. - answer-E) have multiple membrane-spanning
helical domains.
Protein kinase A (PKA) is:
A) activated by covalent binding of cyclic AMP.
B) affected by cyclic AMP only under unusual circumstances.
2025 LATEST UPDATE ALREADY GRADED A+
The type of membrane transport that uses ion gradients as the energy source is:
A) facilitated diffusion
B) passive transport.
C) primary active transport.
D) secondary active transport.
E) simple diffusion. - answer-D) secondary active transport.
An electrogenic Na+ transporter:
A) catalyzes facilitated diffusion of Na+ from a region of high Na+ concentration to one of lower Na+
concentration.
B) must catalyze an electron transfer (oxidation-reduction) reaction simultaneously with Na+
transport.
C) must transport both Na+ and a counterion (Cl-, for example).
D) transports Na+ against its concentration gradient.
E) transports Na+ without concurrent transport of any other charged species. - answer-E) transports Na+
without concurrent transport of any other charged species.
Movement of water across membranes is facilitated by proteins called:
A) annexins.
B) aquaporins.
C) hydropermeases.
D) selectins.
E) transportins. - answer-B) aquaporins.
The specificity of the potassium channel for K+ over Na+ is mainly the result of the:
A) differential interaction with the selectivity filter protein.
B) hydrophobicity of the channel.
,C) phospholipid composition of the channel.
D) presence of carbohydrates in the channel.
E) presence of cholesterol in the channel. - answer-A) differential interaction with the selectivity filter
protein.
A ligand-gated ion channel (such as the nicotinic acetylcholine receptor) is:
A) a charged lipid in the membrane bilayer that allows ions to pass through.
B) a membrane protein that permits a ligand to pass through the membrane only when opened by the
appropriate ion.
C) a membrane protein that permits an ion to pass through the membrane only when opened by the
appropriate ligand.
D) a molecule that binds to the membrane thereby allowing ions to pass through.
E) always requires a second ligand to close the channel once it is opened. - answer-C) a membrane
protein that permits an ion to pass through the membrane only when opened by the appropriate ligand.
Which of the following is not involved in the specificity of signal transduction?
A) Interactions between receptor and signal molecules
B) Location of receptor molecules
C) Structure of receptor molecules
D) Structure of signal molecules
E) Transmembrane transport of signal molecules by receptor molecules - answer-E) Transmembrane
transport of signal molecules by receptor molecules
Scatchard analysis can provide information on:
A) enzyme cascades.
B) enzyme mechanisms.
C) gated ion channels.
D) protein phosphorylation.
E) receptor-ligand interactions. - answer-E) receptor-ligand interactions.
,The force that drives an ion through a membrane channel depends upon:
A) the charge on the membrane.
B) the difference in electrical potential across the membrane.
C) the size of the channel.
D) the size of the ion.
E) the size of the membrane. - answer-B) the difference in electrical potential across the membrane.
The ion channel that opens in response to acetylcholine is an example of a ____________ signal
transduction system.
A) G protein
B) ligand-gated
C) receptor-enzyme
D) serpentine receptor
E) voltage-gated - answer-B) ligand-gated
The effects of acetylcholine on the postsynaptic ion channel are mainly due to:
A) cyclic nucleotide synthesis.
B) protein cleavage (proteolysis).
C) protein conformational changes.
D) protein phosphorylation.
E) protein synthesis. - answer-C) protein conformational changes.
Which of the following statements concerning signal transduction by the insulin receptor is not correct?
A) Activation of the receptor protein kinase activity results in the activation of additional protein
kinases.
B) Binding of insulin to the receptor activates a protein kinase.
C) Binding of insulin to the receptor results in a change in its quaternary structure.
D) The receptor protein kinase activity is specific for tyrosine residues on the substrate proteins.
, E) The substrates of the receptor protein kinase activity are mainly proteins that regulate transcription. -
answer-E) The substrates of the receptor protein kinase activity are mainly proteins that regulate
transcription.
Which of the following statements concerning receptor enzymes is correct?
A) They are not usually membrane-associated proteins.
B) They contain an enzyme activity that acts upon a cytosolic substrate.
C) They contain an enzyme activity that acts upon the extracellular ligand.
D) They have a ligand-binding site on the cytosolic side of the membrane.
E) They have an active site on the extracellular side of the membrane. - answer-B) They contain an
enzyme activity that acts upon a cytosolic substrate.
Guanyl cyclase receptor enzymes:
A) are all membrane-spanning proteins.
B) are examples of ligand-gated ion channels.
C) catalyze synthesis of a phosphate ester.
D) catalyze synthesis of a phosphoric acid anhydride.
E) require hydrolysis of ATP in addition to GTP. - answer-C) catalyze synthesis of a phosphate ester.
Serpentine receptors:
A) are examples of G (GTP-binding) regulatory proteins.
B) are mainly involved in the regulation of ion transport.
C) are present in prokaryotic cells but not in eukaryotic cells.
D) are present in the nucleus and affect gene expression.
E) have multiple membrane-spanning helical domains. - answer-E) have multiple membrane-spanning
helical domains.
Protein kinase A (PKA) is:
A) activated by covalent binding of cyclic AMP.
B) affected by cyclic AMP only under unusual circumstances.
