Biology Exam Question Paper and Answers -2
1. Which of the following substances bind to a site on the intracellular surface of aspanning protein in the plasma-membrane?
A. Parathyroid Hormone (PTH).
B. Vasopressin.
C. ATP.
D. A and B.
E. A and C.
F. B and C.
G. A, B, and C.
H. None of the above.
2. Which of the following serves as a ligand that binds to a receptor site on a ligand-gatedion channel?A. Strychnine.
B. Curare.
C. Muscarine.
D. A and B.
E. A and C.
F. B and C.
G. A, B, and C.
H. None of the above.
3. Which of the following occur in response to an increase in the length of the right kneeextensors in response to a quick tap applied to the right patellar tendon? An increase inthe amount of
A. ACh (acetylcholine) released from central axon terminals of IA muscle-spindlestretch receptor neurons whose peripheral axon terminals are in the right kneeextensor muscle.
B. glutamate bound to AMPA Receptors in the plasma membranes of right kneeextensor motor neurons.
C. potassium conductance in the sarcoplasmic reticulum membranes of right kneeextensor muscles.
D. A and B.
E. A and C.
F. B and C.
G. A, B, and C.
H. None of the above.
4. Person Z swallowed a large amount of substance X and, as a result, has convulsions(abnormal violent contractions of skeletal muscles). Swallowing which of the followingsubstances could lead to convulsions?A. An agonist of the glycine receptor.
B. An antagonist of the nicotinic ACh receptor.
C. A blocker of the voltage-gated sodium channel.
D. A and B.
E. A and C.
F. B and C.
G. A, B, and C.
H. None of the above.
5 Neuron A is a healthy neuron with all the usual ion channels. When at rest with amembrane voltage of R millivolts, neuron A produces no action potentials. The voltagethreshold for an action potential in neuron A is T millivolts. T is greater than R; T is lessthan zero. In addition, neuron A’s membrane includes the membrane-spanningmolecule Z with an ion channel that opens when neurotransmitter Y binds to theY receptor site on the extracellular surface of Z. The Nernst equilibrium potential for Z’sion channel is E millivolts. Neuron B synapses on neuron A; neuron B’s neurotransmitteris neurotransmitter Y. Which of the following statements are true when neuron A isinitially at rest and neuron B releases neurotransmitter Y?
A. If the value of R is less than E, if the value of E is less than T, and if chloride isthe only ion that passes through open Z channels, then Y’s binding to its receptorsite on Z in neuron A produces a decrease in the amount of intracellular chlorideions in neuron A.
B. If the value of E is zero and if both sodium ions and potassium ions pass throughopen Z channels, then Y’s binding to its receptor site on Z in neuron A producesan increase in the amount of intracellular potassium ions in neuron A.
C. If the value of E is equal to R, and if chloride is the only ion that passes throughopen Z channels, then Y’s binding to its receptor site on Z in neuron A producesno change in the chloride conductance of neuron A.
D. A and B.
E. A and C.
F. B and C.
G. A, B, and C.
H. None of the above.
6. Consider a system that contains three neurons in a culture dish bathed in normalphysiological saline. All three neurons are healthy. Neuron A synapses onto Neuron B.Neuron B synapses onto Neuron C. Neuron A has glycine in its synaptic vesicles.Neuron B has GABA in its synaptic vesicles. The only ligand-gated receptors inNeuron A are AMPA channels. The only ligand-gated receptors in the plasmamembrane of Neuron B are glycine receptors. The only ligand-gated receptors in theplasma membrane of Neuron C are GABAAreceptors. All 3 neurons have no otherligand-gated receptors in their plasma membranes. All 3 neurons have a sodiumequilibrium potential of +60 millivolts. All 3 neurons have a potassium equilibriumpotential of -86 millivolts. All 3 neurons a chloride equilibrium potential ofzero (0) millivolts. The threshold for an action potential in all 3 neurons is -55 millivolts.At 1:55 AM, glutamate is added to the physiological saline. At 2:00 AM, the actionpotential firing rate of each neuron is 100 Hz. Which of the following will lead to adecrease in Neuron C’s action potential firing rate?
A. At 2:01 AM, glycine is added to the bath.
B. At 2:01 AM, strychnine is added to the bath.
C. At 2:01 AM, CNQX is added to the bath.
D. A and B.E. A and C.
F. B and C.G. A, B, and C.
H. None of the above.
7. Consider Neuron B in the frog central nervous system whose plasma membrane has anewly discovered ligand-gated ionotropic receptor, named the LIGD receptor. Thechannel in the same molecular complex as the LIGD receptor is termed the LIGDreceptor channel. The Nernst equilibrium potential for sodium in Neuron B is +100 mV,and the Nernst equilibrium potential for potassium in Neuron B is -100 mV.The threshold for an action potential in Neuron B is -65 mV and the resting potential forNeuron B is -75 mV. LIGD is an agonist for the ligand-gated ionotropic receptor. WhenLIGD binds to its binding site, there is an increase in conductance of the LIGD receptorchannel. Neuron A synapses onto Neuron B. Neuron A’s transmitter is LIGD.
A. Consider the situation that when the LIGD receptor channel is open in Neuron B,it is permeable to both sodium and potassium. For this situation, when open, it ispermeable to no other ions. For this situation, when open, its potassiumconductance equals nine times its sodium conductance. For this situation, inresponse to an action potential in Neuron A, then there will be a voltagedecrease and an inhibitory postsynaptic potential in Neuron B.
B. Consider the situation that when the LIGD receptor channel is open in Neuron B,it is permeable to both sodium and potassium. For this situation, when open, it ispermeable to no other ions. For this situation, when open, its potassiumconductance equals seven times its sodium conductance. For this situation, inresponse to an action potential in Neuron A, then there will be a voltagedecrease and an inhibitory postsynaptic potential in Neuron B.
C. Consider the situation that when the LIGD receptor channel is open in Neuron B,it is permeable to both sodium and potassium. For this situation, when open, it ispermeable to no other ions. For this situation, when open, its potassiumconductance equals four times its sodium conductance. For this situation, inresponse to an action potential in Neuron A, then there will be a voltage increaseand an excitatory postsynaptic potential in Neuron B.
D. A and B.
E. A and C.
F. B and C.
G. A, B, and C.
H. None of the above.
8. Which of the following are ligands that bind to the nicotinic Acetylcholine Receptor(nAChR)?
A. Curare.
B. Nicotine.
C. Muscarine.
D. A and B.
E. A and C.
F. B and C.
G. A, B, and C.
H. None of the above.
9. Consider Neuron B in the frog central nervous system whose plasma membrane has apreviously unknown channel that is selectively conductive to a newly discovered divalentcation named DIVCAT with a valence of +2. The threshold for an action potential inNeuron B is -55 millivolts and the resting potential for Neuron B is -70 millivolts. TheDIVCAT channel in Neuron B is part of an ionotropic receptor with an extracellularbinding site for the newly discovered ligand LGD. When LGD binds to its binding site,there is an increase in the DIVCAT conductance of Neuron B. Neuron A synapses ontoNeuron B. Neuron A’s neurotransmitter is LGD.
A. The intracellular concentration of DIVCAT is 1000 times greater than theextracellular concentration of DIVCAT. In response to an action potential inNeuron A, there will be: a decrease in the membrane voltage of Neuron B;a decrease in the amount of intracellular DIVCAT in Neuron B; andan inhibitory postsynaptic potential in Neuron B.
B. The intracellular concentration of DIVCAT is 100 times greater than theextracellular concentration of DIVCAT. In response to an action potential inNeuron A, there will be: an increase in the membrane voltage of Neuron B;an increase in the amount of intracellular DIVCAT in Neuron B; andan inhibitory postsynaptic potential in Neuron B.C. The intracellular concentration of DIVCAT is 10 times greater than theextracellular concentration of DIVCAT. In response to an action potential inNeuron A, there will be: an increase in the membrane voltage of Neuron B;an increase in the amount of intracellular DIVCAT in Neuron B; andan excitatory postsynaptic potential in Neuron B.
D. A and B.
E. A and C.
F. B and C.
G. A, B, and C.
H. None of the above.
10. A complete motor neuron is removed from a frog and placed in normal physiologicalsaline at 1 AM. The neuron is healthy. At 2 AM, the physiological saline bathing theneuron is removed and replaced with a modified physiological saline. The compositionof the modified physiological saline is as follows: its potassium concentration is the sameas normal physiological saline; its sodium concentration is the same as the intracellularsodium concentration of the motor neuron; its total concentration of solutes (osmolarity)is the same as normal physiological saline. The modified physiological saline alsocontains molecules that block the flux of ions via the sodium-potassium primary activetransport pump. At 2:05 AM, the resting membrane voltage of the neuron is-70 millivolts. At 2:06 AM,
A. an increase in membrane voltage will lead to no change in sodium conductance.
B. the value of the Nernst equilibrium potential for sodium ions for the neuron is lessthan +10 millivolts.
C. an increase in sodium conductance will lead to an increase in the amount ofintracellular sodium.
D. A and B.
E. A and C.
F. B and C.
G. A, B, and C.
H. None of the above.
Answer
1-c , 2-d , 3-b , 4-h , 5-a , 6-f , 7-e , 8-d, 9-h, 10-f