UIC BIOS 286 EXAM 3 STUDY GUIDE COMPLETED WITH SAMPLE
QUESTIONS
What are odorant receptors (e.g., ionotropic vs metabotropic receptors or ion channels or
GPCRs? - correct answer Odorant receptors are g-protein coupled receptors or G.P.C.R.s
Where are odorant receptors expressed specifically? On what part of the ORN? - correct
answer Odorant receptors are expressed almost exclusively in the cilia of olfactory receptor
neurons (ORN).
For example, are ORNs densely expressed in the axonal terminals or in another part of the cell?
- correct answer ORNs would NOT be densley expressed on axonal terminals, cell body, or any
other parts. They would be expressed within the olfactory epithelium, within the mucus layer
on cilia.
Are ORNs inhibitory or excitatory? What NT do they utilize? - correct answer ORNs are
Excitatory and the utilized NT is Glutamate.
Do ORNs regenerate? Where are the cell bodies of ORNs located? - correct answer ORNs do
regenerate and are located in olfactory epithelium.
Where are cilia located and what are cilia? - correct answer Cilia are located within the mucus
layer and cilia are thin protrusions from dendrites of ORNs that contain odorant receptors.
Do odorant receptors have broad or narrow tuning curves? What does it mean in terms of
ligand to receptor binding? - correct answer Odorant receptors generally have broad tuning
curves. To have broad tuning curves in ligand to receptor binding means that a wide variety of
odors can be detected.
If an odorant receptor was narrowly tuned (which some receptors are) than that would mean
they detect very specific odorants.
Does the size of the olfactory epithelium vary amongst species? - correct answer Yes, the size
does very amongst species.
Humans= 10cm^2
Cats=20cm^2
Dogs=170cm^2
Are all odorant receptor genes in the human genome functional? - correct answer No, not all
odorant receptor genes in the human genome are functional.
, In humans there are about 300-400 functional odorant receptors however there's roughly
around 900 total odorant receptors.
Each olfactory receptor neuron expresses the products (proteins) of how many odorant
receptor genes? - correct answer Each ORN expresses the product/protein of only one odorant
receptor gene.
Why can a single ORN be activated/depolarized by multiple odorant molecules - correct answer
The reason a single ORN can be activated/depolarized by multiple odorants is because of the
broad tuning curves that allow it to be stimulated by multiple odorant molecules.
Does it express multiple kinds of odorant receptors on its cilia membrane? - correct answer It
does not express multiple kinds of odorant receptors, only a single ORN expresses one kind of
odorant receptor.
On what part of the neuron should I apply an odorant if I wanted to stimulate that neuron in a
laboratory under experimental conditions? - correct answer You would want to apply the
odorant on the cilia of the neuron.
The reason you would want to apply it on the neuron is because odorant receptors are located
on the cilia.
Olfactory signal transduction in the cilia: opening of what types of membrane channels causes
membrane depolarization? - correct answer Channels that cause depolarization are CNG
channels (which are for Na+ and Ca^2+ influx) and Calcium-gated Cl- channels (for Chlorine
efflux).
What does the G protein activate (what is the enzyme)? - correct answer The G protein
activates adenylyl cyclase (AC) which produces cyclic adenosine monophosphate (cAMP) to
open CNG channels
Olfactory bulbs: what are glomeruli? Do the axons from olf. receptor neurons end in the
glomeruli? - correct answer Glomeruli are structures in the olfactory bulb.
Axons from the olfactory receptor neurons do end in the glomeruli.
Do glomeruli receive input from RANDOM ORNs or from ORNs expressing the products of the
SAME odorant receptor genes? - correct answer Glomeruli receive input from ORNs expressing
the products of the same odorant receptor gene.
Do olfactory bulbs project directly to primary or secondary olf. cortex? 2.Via what tract? -
correct answer They project directly to the primary olf. cortex.
2.Via the olfactory tract.
QUESTIONS
What are odorant receptors (e.g., ionotropic vs metabotropic receptors or ion channels or
GPCRs? - correct answer Odorant receptors are g-protein coupled receptors or G.P.C.R.s
Where are odorant receptors expressed specifically? On what part of the ORN? - correct
answer Odorant receptors are expressed almost exclusively in the cilia of olfactory receptor
neurons (ORN).
For example, are ORNs densely expressed in the axonal terminals or in another part of the cell?
- correct answer ORNs would NOT be densley expressed on axonal terminals, cell body, or any
other parts. They would be expressed within the olfactory epithelium, within the mucus layer
on cilia.
Are ORNs inhibitory or excitatory? What NT do they utilize? - correct answer ORNs are
Excitatory and the utilized NT is Glutamate.
Do ORNs regenerate? Where are the cell bodies of ORNs located? - correct answer ORNs do
regenerate and are located in olfactory epithelium.
Where are cilia located and what are cilia? - correct answer Cilia are located within the mucus
layer and cilia are thin protrusions from dendrites of ORNs that contain odorant receptors.
Do odorant receptors have broad or narrow tuning curves? What does it mean in terms of
ligand to receptor binding? - correct answer Odorant receptors generally have broad tuning
curves. To have broad tuning curves in ligand to receptor binding means that a wide variety of
odors can be detected.
If an odorant receptor was narrowly tuned (which some receptors are) than that would mean
they detect very specific odorants.
Does the size of the olfactory epithelium vary amongst species? - correct answer Yes, the size
does very amongst species.
Humans= 10cm^2
Cats=20cm^2
Dogs=170cm^2
Are all odorant receptor genes in the human genome functional? - correct answer No, not all
odorant receptor genes in the human genome are functional.
, In humans there are about 300-400 functional odorant receptors however there's roughly
around 900 total odorant receptors.
Each olfactory receptor neuron expresses the products (proteins) of how many odorant
receptor genes? - correct answer Each ORN expresses the product/protein of only one odorant
receptor gene.
Why can a single ORN be activated/depolarized by multiple odorant molecules - correct answer
The reason a single ORN can be activated/depolarized by multiple odorants is because of the
broad tuning curves that allow it to be stimulated by multiple odorant molecules.
Does it express multiple kinds of odorant receptors on its cilia membrane? - correct answer It
does not express multiple kinds of odorant receptors, only a single ORN expresses one kind of
odorant receptor.
On what part of the neuron should I apply an odorant if I wanted to stimulate that neuron in a
laboratory under experimental conditions? - correct answer You would want to apply the
odorant on the cilia of the neuron.
The reason you would want to apply it on the neuron is because odorant receptors are located
on the cilia.
Olfactory signal transduction in the cilia: opening of what types of membrane channels causes
membrane depolarization? - correct answer Channels that cause depolarization are CNG
channels (which are for Na+ and Ca^2+ influx) and Calcium-gated Cl- channels (for Chlorine
efflux).
What does the G protein activate (what is the enzyme)? - correct answer The G protein
activates adenylyl cyclase (AC) which produces cyclic adenosine monophosphate (cAMP) to
open CNG channels
Olfactory bulbs: what are glomeruli? Do the axons from olf. receptor neurons end in the
glomeruli? - correct answer Glomeruli are structures in the olfactory bulb.
Axons from the olfactory receptor neurons do end in the glomeruli.
Do glomeruli receive input from RANDOM ORNs or from ORNs expressing the products of the
SAME odorant receptor genes? - correct answer Glomeruli receive input from ORNs expressing
the products of the same odorant receptor gene.
Do olfactory bulbs project directly to primary or secondary olf. cortex? 2.Via what tract? -
correct answer They project directly to the primary olf. cortex.
2.Via the olfactory tract.
