Physio 1 Study Questions
Exam 2
Nervous
1. Describe the chemical structure of a phospholipid molecule typically found in cell membranes. Which part is polar?
Non- polar? Water soluble? Water insoluble? Look up the full chemical structure of a ‘phosphatidylcholine’ molecule.
This is the actual structure of the phospholipid molecule found in cell membranes. Identify the three carbons of the
glycerol. Identify the two long chain fatty acid tails attached to two of the glycerol carbons. Identify the charged head
containing the phosphate and the ‘choline’ groups. Note the locations of the charges. Do you see why the head is polar
and the fatty acid tails are non-polar?
2. Describe the molecular structure of cell membranes. What is meant by the term “bilipid layer”? What is the relative
percentage composition of phospholipids and proteins in cell membrane structure? Give six different functions for
proteins found in cell membranes. Is the cell membrane structure of a Golgi complex different from the cell membrane
structure of a mitochondrion? Endoplasmic reticulum? Plasma membrane? Lysosomal membrane? Nuclear membrane?
The answer is yes. Different membrane proteins impart different functions to each membrane.
3. O2, CO2, and lipids easily diffuse through the bilipid layer of cell membranes? Why?
4. Water, amino acids, and simple sugars do NOT easily diffuse through the bilipid layer of cell membranes? Why?
5. The extracellular and intracellular fluids are often described as “bulk fluids”. Though the chemical identities of the
solutes in these fluids are different, the fluids’ total solute concentrations are the same, that is, the intra- and extracellular
fluids are isotonic. Their osmolarities are equivalent. Note further that bulk fluids contain high concentrations of positive
and negative ions. Yet, bulk fluids are electrically neutral, ie. the bulk fluids have overall net charge of zero. Explain
chemically how is this possible?
6. What are the structural and functional characteristics of ion channels? Are ion channels specific to each ion? If so,
how? In what way can an individual cell become more or less permeable to a specific ion? What is the term for this?
7. What are gated ion channels? Distinguish between ligand-gated, mechanical-gated, and voltage-gated ion channels.
How do each of these types of channels work?
8. Will polar molecules like glucose and amino acids diffuse through the bilipid layer? Do glucose and amino acids use
ion channels? How do polar molecules travel across cell membranes? How do carrier proteins work?
9. Both ion channels and carrier proteins use passive diffusion, that is, they use the energy of chemical gradients. Second
law thermodynamics: all things proceed spontaneously from higher energy states to lower energy states. Diffusion
gradients from high to low concentrations essentially are different energy states. High concentration areas have more
molecular energy than lower concentration areas. Thus molecules move from high energy, high concentration to areas of
lower energy, lower concentration areas. With diffusion, no energy needs to be added to the system. The energy (random
molecular motion) is already there. Note: It is passive diffusion when oxygen and carbon dioxide molecules diffuse
directly through the bilipid layer. It is also passive diffusion when ions flow through ion channels, and when carrier
proteins move polar molecules through cell membranes. Carrier proteins mediate the slowest rates of diffusion. Ion
channels enable much faster rates of diffusion. Why?
10. If a cell needs to increase or decrease the diffusion rate through a membrane of a particular ion or polar molecule, the
cell can increase or decrease the number of ion channels or carrier proteins in that membrane. Increasing the number of
channels or carriers is called ‘upregulation’ , decreasing their number is called ‘ downregulation’. In this way the cell can
control the relative permeabilities of its membranes to different ions and polar molecules.
11. When ion channels and carrier proteins are used, this type of passive transport is called facilitated or mediated
diffusion as opposed to simple diffusion through membranes without the aid of membrane proteins. Active transport is
the movement of molecules across a membrane by a carrier protein that requires energy. Active transport proteins move
molecules against their concentration gradient, ie. from low concentration to high concentration. Describe the
sodium/potassium active transport pump and explain how it works. What exact roles do ATP and P i play in the Na+/K+
active transport pump? How many Na+ ions are transported out, and K+ ions transported in with the hydrolysis of one
ATP? The sodium/potassium active transport pump is an example of primary active transport. What is secondary active
transport and how does it work? Does it use ATP directly? If not, what does it use? What are co-transporters and
counter-transporters and how does each work? Give one example of a co-transporter and specify the solutes being
transported. Give one example of a counter-transporter and specify the solutes transported.
12. In what types of cells do you find the sodium/potassium ATP pump in the body? When is it active?
13. Learn the millimolar (mM) concentrations of Na+, K+, Cl-, Ca++ ions, and inorganic phosphate, P i , in both the
intracellular and extracellular fluids. Memorize these. To do so will be a great help to you as you proceed through the
course.
1
, 14. Compare the extracellular ion concentrations to their respective intracellular concentrations. Determine the
magnitudes of the differences between intracellular and extracellular concentrations for each ion.
15. What is the Potassium (K+) equilibrium potential? Describe how it is produced? What is its value? What is the
Sodium (Na+) equilibrium potential? Describe how it is produced. What is its value? How do the K+ and Na+
equilibrium potentials combine to produce the Resting Membrane Potential? It is important that you understand this.
16. We know that bulk fluids have electrical neutrality, yet a membrane potential (ie. a voltage across the membrane) still
exists. How is this possible? As determined above, the membrane potential results from the combination of diffusion and
electrical gradients for both K+ ion and Na+ ion. What is often not understood is that the positive and negative charges
lining the membrane comprise only an infinitesimal number of ions. Compared to the ion concentrations of the bulk
fluids, their number is insignificant. It is only this small number of ions at the inner and outer surfaces of the plasma
membrane that is responsible for the membrane potential. Even with the membrane potential, the bulk fluids remain
electrically neutral. The action potential, too, is produced by the flux of a comparatively small number of ions across the
plasma membrane of the axon.
17. Describe in detail the events of the action potential. Identify all ion channels involved, how and when the ion
channels open and close, and how the membrane potential changes in response to changes in ion channel permeabilities.
Define the terms: threshold, depolarization, repolarization, and hyperpolarization. At what voltage in a typical nerve cell
do sodium channels open, inactivate, close? At what voltage do potassium ions open? Close?
18. What is meant by the “all-or-none law” of action potentials? Thousands of action potentials are still possible in a
neuron even if the Na+/K+ pumps cease to work. How can you explain this fact?
19. What is the duration of the action potential? The amplitude? Do these parameters of axon potentials change with
different intensities of stimulus?
20. How are increasingly stronger stimuli transmitted by action potentials along an axon?
21. What is the refractory period of the action potential? What role does it serve in the propagation of the action
potential?
22. Describe the specific chemical and cellular events enabling the action potential to propagate down the axon?
24. What factors influence the speed of conduction of an action potential down an axon? Axon diameter is important.
Why? Myelin is important. Why?
25. What is myelin? How does it form? What happens at the node of Ranvier? How much faster does the action
potential travel in a myelinated neuron compared to an unmyelinated one? What is meant by the cable properties of an
axon and why are cable properties important? Which direction do sodium ions flow in axon cytoplasm? Which direction
do action potentials propagate? Why don’t action potentials propagate both ways along an axon?
26. What is multiple sclerosis, ie. MS? What are the clinical symptoms of MS? Explain in terms of what you know
about myelinated neurons.
27. How are different stimulus intensities conveyed by action potentials if action potentials always have the same
magnitude and timing?
28. What happens when an action potential reaches the synaptic bulb? Define ‘synapse’? Synaptic cleft? Presynaptic
cell? Postsynaptic cell? Synaptic vesicle? Neurotransmitter?
29. What roles do voltage-gated calcium ion channels play in the release of neurotransmitter from the synaptic bulb?
What role does the protein calmodulin play? What are snare proteins and what is their function? What effect does
botulism toxin have on snare proteins of cholinergic neurons? Explain the mechanisms by which synaptic vesicles store
and release neurotransmitters?
30. Acetycholine was the first neurotransmitter discovered. It is the major neurotransmitter released at neuromuscular
junctions of skeletal muscle. Draw the structure of acetylcholine. Identify the 2-carbon acetyl group and the choline
group. The acetyl group should be quite familiar to you now. Where else have you seen the choline group?
31. Describe the Nicotinic ACh (acetycholine) receptor. How does it work? Give specific examples of where it is found
in the body? Why is it called a nicotinic ACh receptor?
32. What is the role of acetylcholinesterase enzyme? Where is it located specifically? What is the substrate of
acetylcholinesterase enzyme. What are the products? What is the fate of the products? How are the products recycled
back to the synaptic bulb. Identify the two specific types of membrane transporters used to move neurotransmitter into
synaptic vesicles. See your handouts.
33. ACh binding to ACh receptors creates a graded potential in the postsynaptic cell. What is a graded potential? In
what ways does a graded potential differ from an action potential?
34. Graded potentials can be excitatory postsynaptic potentials (EPSP) or inhibitory postsynaptic potentials (IPSP).
Which is created at the ACh receptor?
2
Exam 2
Nervous
1. Describe the chemical structure of a phospholipid molecule typically found in cell membranes. Which part is polar?
Non- polar? Water soluble? Water insoluble? Look up the full chemical structure of a ‘phosphatidylcholine’ molecule.
This is the actual structure of the phospholipid molecule found in cell membranes. Identify the three carbons of the
glycerol. Identify the two long chain fatty acid tails attached to two of the glycerol carbons. Identify the charged head
containing the phosphate and the ‘choline’ groups. Note the locations of the charges. Do you see why the head is polar
and the fatty acid tails are non-polar?
2. Describe the molecular structure of cell membranes. What is meant by the term “bilipid layer”? What is the relative
percentage composition of phospholipids and proteins in cell membrane structure? Give six different functions for
proteins found in cell membranes. Is the cell membrane structure of a Golgi complex different from the cell membrane
structure of a mitochondrion? Endoplasmic reticulum? Plasma membrane? Lysosomal membrane? Nuclear membrane?
The answer is yes. Different membrane proteins impart different functions to each membrane.
3. O2, CO2, and lipids easily diffuse through the bilipid layer of cell membranes? Why?
4. Water, amino acids, and simple sugars do NOT easily diffuse through the bilipid layer of cell membranes? Why?
5. The extracellular and intracellular fluids are often described as “bulk fluids”. Though the chemical identities of the
solutes in these fluids are different, the fluids’ total solute concentrations are the same, that is, the intra- and extracellular
fluids are isotonic. Their osmolarities are equivalent. Note further that bulk fluids contain high concentrations of positive
and negative ions. Yet, bulk fluids are electrically neutral, ie. the bulk fluids have overall net charge of zero. Explain
chemically how is this possible?
6. What are the structural and functional characteristics of ion channels? Are ion channels specific to each ion? If so,
how? In what way can an individual cell become more or less permeable to a specific ion? What is the term for this?
7. What are gated ion channels? Distinguish between ligand-gated, mechanical-gated, and voltage-gated ion channels.
How do each of these types of channels work?
8. Will polar molecules like glucose and amino acids diffuse through the bilipid layer? Do glucose and amino acids use
ion channels? How do polar molecules travel across cell membranes? How do carrier proteins work?
9. Both ion channels and carrier proteins use passive diffusion, that is, they use the energy of chemical gradients. Second
law thermodynamics: all things proceed spontaneously from higher energy states to lower energy states. Diffusion
gradients from high to low concentrations essentially are different energy states. High concentration areas have more
molecular energy than lower concentration areas. Thus molecules move from high energy, high concentration to areas of
lower energy, lower concentration areas. With diffusion, no energy needs to be added to the system. The energy (random
molecular motion) is already there. Note: It is passive diffusion when oxygen and carbon dioxide molecules diffuse
directly through the bilipid layer. It is also passive diffusion when ions flow through ion channels, and when carrier
proteins move polar molecules through cell membranes. Carrier proteins mediate the slowest rates of diffusion. Ion
channels enable much faster rates of diffusion. Why?
10. If a cell needs to increase or decrease the diffusion rate through a membrane of a particular ion or polar molecule, the
cell can increase or decrease the number of ion channels or carrier proteins in that membrane. Increasing the number of
channels or carriers is called ‘upregulation’ , decreasing their number is called ‘ downregulation’. In this way the cell can
control the relative permeabilities of its membranes to different ions and polar molecules.
11. When ion channels and carrier proteins are used, this type of passive transport is called facilitated or mediated
diffusion as opposed to simple diffusion through membranes without the aid of membrane proteins. Active transport is
the movement of molecules across a membrane by a carrier protein that requires energy. Active transport proteins move
molecules against their concentration gradient, ie. from low concentration to high concentration. Describe the
sodium/potassium active transport pump and explain how it works. What exact roles do ATP and P i play in the Na+/K+
active transport pump? How many Na+ ions are transported out, and K+ ions transported in with the hydrolysis of one
ATP? The sodium/potassium active transport pump is an example of primary active transport. What is secondary active
transport and how does it work? Does it use ATP directly? If not, what does it use? What are co-transporters and
counter-transporters and how does each work? Give one example of a co-transporter and specify the solutes being
transported. Give one example of a counter-transporter and specify the solutes transported.
12. In what types of cells do you find the sodium/potassium ATP pump in the body? When is it active?
13. Learn the millimolar (mM) concentrations of Na+, K+, Cl-, Ca++ ions, and inorganic phosphate, P i , in both the
intracellular and extracellular fluids. Memorize these. To do so will be a great help to you as you proceed through the
course.
1
, 14. Compare the extracellular ion concentrations to their respective intracellular concentrations. Determine the
magnitudes of the differences between intracellular and extracellular concentrations for each ion.
15. What is the Potassium (K+) equilibrium potential? Describe how it is produced? What is its value? What is the
Sodium (Na+) equilibrium potential? Describe how it is produced. What is its value? How do the K+ and Na+
equilibrium potentials combine to produce the Resting Membrane Potential? It is important that you understand this.
16. We know that bulk fluids have electrical neutrality, yet a membrane potential (ie. a voltage across the membrane) still
exists. How is this possible? As determined above, the membrane potential results from the combination of diffusion and
electrical gradients for both K+ ion and Na+ ion. What is often not understood is that the positive and negative charges
lining the membrane comprise only an infinitesimal number of ions. Compared to the ion concentrations of the bulk
fluids, their number is insignificant. It is only this small number of ions at the inner and outer surfaces of the plasma
membrane that is responsible for the membrane potential. Even with the membrane potential, the bulk fluids remain
electrically neutral. The action potential, too, is produced by the flux of a comparatively small number of ions across the
plasma membrane of the axon.
17. Describe in detail the events of the action potential. Identify all ion channels involved, how and when the ion
channels open and close, and how the membrane potential changes in response to changes in ion channel permeabilities.
Define the terms: threshold, depolarization, repolarization, and hyperpolarization. At what voltage in a typical nerve cell
do sodium channels open, inactivate, close? At what voltage do potassium ions open? Close?
18. What is meant by the “all-or-none law” of action potentials? Thousands of action potentials are still possible in a
neuron even if the Na+/K+ pumps cease to work. How can you explain this fact?
19. What is the duration of the action potential? The amplitude? Do these parameters of axon potentials change with
different intensities of stimulus?
20. How are increasingly stronger stimuli transmitted by action potentials along an axon?
21. What is the refractory period of the action potential? What role does it serve in the propagation of the action
potential?
22. Describe the specific chemical and cellular events enabling the action potential to propagate down the axon?
24. What factors influence the speed of conduction of an action potential down an axon? Axon diameter is important.
Why? Myelin is important. Why?
25. What is myelin? How does it form? What happens at the node of Ranvier? How much faster does the action
potential travel in a myelinated neuron compared to an unmyelinated one? What is meant by the cable properties of an
axon and why are cable properties important? Which direction do sodium ions flow in axon cytoplasm? Which direction
do action potentials propagate? Why don’t action potentials propagate both ways along an axon?
26. What is multiple sclerosis, ie. MS? What are the clinical symptoms of MS? Explain in terms of what you know
about myelinated neurons.
27. How are different stimulus intensities conveyed by action potentials if action potentials always have the same
magnitude and timing?
28. What happens when an action potential reaches the synaptic bulb? Define ‘synapse’? Synaptic cleft? Presynaptic
cell? Postsynaptic cell? Synaptic vesicle? Neurotransmitter?
29. What roles do voltage-gated calcium ion channels play in the release of neurotransmitter from the synaptic bulb?
What role does the protein calmodulin play? What are snare proteins and what is their function? What effect does
botulism toxin have on snare proteins of cholinergic neurons? Explain the mechanisms by which synaptic vesicles store
and release neurotransmitters?
30. Acetycholine was the first neurotransmitter discovered. It is the major neurotransmitter released at neuromuscular
junctions of skeletal muscle. Draw the structure of acetylcholine. Identify the 2-carbon acetyl group and the choline
group. The acetyl group should be quite familiar to you now. Where else have you seen the choline group?
31. Describe the Nicotinic ACh (acetycholine) receptor. How does it work? Give specific examples of where it is found
in the body? Why is it called a nicotinic ACh receptor?
32. What is the role of acetylcholinesterase enzyme? Where is it located specifically? What is the substrate of
acetylcholinesterase enzyme. What are the products? What is the fate of the products? How are the products recycled
back to the synaptic bulb. Identify the two specific types of membrane transporters used to move neurotransmitter into
synaptic vesicles. See your handouts.
33. ACh binding to ACh receptors creates a graded potential in the postsynaptic cell. What is a graded potential? In
what ways does a graded potential differ from an action potential?
34. Graded potentials can be excitatory postsynaptic potentials (EPSP) or inhibitory postsynaptic potentials (IPSP).
Which is created at the ACh receptor?
2
