Name(s):
Period:
Date:
Smell Lab – Receptors in Action
HASPI Medical Chemistry Lab
Background/Introduction
A doctor will prescribe specific medications for each sickness a patient might have. In the body, each
medication acts differently based on its chemical structure, as it interacts with specific receptors that will
result in physiological changes to help you the patient fight whatever they have. Lets take a look at a few
different structures.
The first medication is aspirin. Aspirin is a pain reliever, also known as an analgesic medicine. The next
medication is methylsalicylate. You might see that it is very similar to aspirin, however, methylsalicylate
is an antibacterial substance that you will find in your
Aspirin
Methylsalicylate Loratadine Diphenhydramine
mouthwash. The third molecule looks completely
different. This molecule is loratadine, also known as
Claritin. Loratadine is an antihistamine molecule. The
last molecule is diphenhydramine, also known as
Benadryl, another antihistamine.
v
The shape of each molecule is specific to the receptor it
will find in the body. A receptor is any place in the body
where a drug can selectively bind. A medication is taken
to help with a specific problem, so once the bloodstream
is full of the medication it bounces around the body until
it meets with a receptor it will fit in.
http://www.adcock.co.za/images/histamine.jpg
We design medications to fit in receptors that control
certain responses in the body. Usually, the part of the medication that will fit in the receptor looks a lot
like the molecule that normally fits in the receptor. Pain medications fit in our pain receptors.
Antihistamines are able to reduce our body’s immune response against common allergens by binding to
block the histamines from binding. Heart medications are designed to interact only with receptors in
certain parts of our hearts. A receptor is almost like a lock, and the medication fits in the lock like a key.
When a receptor is activated there are different responses that can occur. Some medications then turn on
the receptor and start a physiological response by sending a signal to the brain. Some medications sit in
the receptor and block other molecules from starting a response. In some cases, the medicine binds to a
receptor in an enzyme or other protein, causing it to change its shape and activity.
Sometimes a medication will fit in other receptors in addition to the target. This causes side effects.
Sometimes a new medication might work really well, but because of side effects we will never find it in
the stores because it will not pass approval by the FDA. Some medicines are still used despite the side
effects because they are so effective at what they do. If you have ever had a strong allergic reaction you
might have taken a Benadryl, known generically as diphenhydramine. Benadryl not only works on your
skin cells to help with a rash, but it is a molecule that can pass through what is called the blood brain
barrier and interact with receptors in the brain. Ultimately, this causes you to become very drowsy.
Medicines that make us drowsy can be very dangerous, and can limit your ability to take them. You
cannot drive a car if you are too drowsy, and you might have a hard time getting any work done.
Smell Lab –Receptors in Action , HASPI Medical Chemistry Lab
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Scientists looked at the diphenhydramine molecule and began to design
other molecules that look similar to diphenhydramine but cannot cross the
blood brain barrier. This lead to a second generation of antihistamines like
Claritin and Zyrtec. Although these drugs are less effective against
allergens, they can be taken daily, so they are a great choice as a preventative
daily drug for people who suffer from allergies. If you look at the two drugs
you can see that there are some similarities, which allow them both to bind to
histamine receptors, but that there are differences that change their side effects.
Loratidine
(Claritin)
Diphenhydramine
(Benadryl)
In some cases the different shape of the two molecules can completely change
their medicinal qualities. Take a look at the other pair of molecules from the
beginning of the lab. You might think they look very similar. In fact, in less than
30 minutes you can do a reaction with just two simple ingredients which will
Aspirin
Methylsalicylate
turn Aspirin into Methylsalicylate. This actually changes a lot of the
properties, changing it from a crystal into an oil, and significantly changing
the smell so that it is a strong mint smell. These two molecules will no longer fit in the same receptor,
which is why they then have different medicinal properties.
v
Lab Scenario
In this class we cannot give you a lot of different medications to
see what happens, but we can test a group of similarly sized
molecules and see how they interact with receptors. Today you
will take a look at 15 different molecules that interact with your
nasal receptors and help you to smell. Their shape determines
which receptors they interact with, causing you to smell
different classes of molecules in different ways.
As the molecule interacts with the receptor a signal is sent to
the brain. In the brain, the signal is interpreted as a specific
smell. This is just like the signals sent when a medication
interacts with a receptor within your body.
As you smell each medicine be careful to waft each scent as
they can be very overwhelming in some cases.
http://health.howstuffworks.com/mentalhealth/human-nature/perception/smell2.htm
Pre Lab Questions
1.
2.
3.
4.
What is a receptor?
What causes a drug to interact with a receptor?
What responses may occur if a receptor is activated?
Analyze the following statement: If two drugs look similar they will have similar effects.
a. Is this always true, sometimes true or never true?
b. Explain your answer
5. How are scents similar to medications?
6. What can a scientist take into account when designing a drug for a specific receptor?
7. What is a cause of side effects?
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Smell Lab –Receptors in Action , HASPI Medical Chemistry Lab
Name(s):
Period:
Date:
Smell Lab – Receptors in Action
HASPI Medical Chemistry Lab
Procedure
In this lab your goal is to try to identify each smell and note any relationships between molecules with the
same functional groups. Follow along as your teacher runs the PowerPoint presentation to better
understand what each molecule is made of and how the structure affects the activity of the molecule.
Part A: Aldehydes
Molecule
Odor 1 O
H3 C
O
Odor 2
Odor 3
Odor 2
Odor 3
H
HO
Smell Prediction
1. Each of these molecules has a different odor.
Explain why:
2. Aldehydes are a family of organic molecules
because they all share something in common.
In looking at the three molecules in part A and
the one shown below, decide what is the
unifying pattern that makes
all of these molecules
aldehydes and draw
it in space to the right.
Actual Smell
Odor 1
Part B: Esters
Molecule
Odor 4
Odor 5
Odor 6
Smell Prediction
Smell Lab –Receptors in Action , HASPI Medical Chemistry Lab
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1. The odors 4, 5 and 6, are part of the family of
molecules called esters.
Try to find the common pattern within the
family of esters and draw it on the right
Most organic molecules are largely made of
carbon (C) and hydrogen (H) atoms. Because
of this, it is often distracting to draw in every
carbon and hydrogen atom in a molecular
structure. So scientists often draw the organic
molecules in a short-hand version where the
carbon atoms are inferred by the points of
lines and shapes.
a. How many carbon atoms
and hydrogen atoms do you
see in the short-hand version
of Odor 4?
C=
H=
b. How many carbon atoms
and hydrogen atoms do you
see in the full atom version of
odor 4?
c. Compare the 2 versions of
Odor 4. What does the
number 3 on the H3
represent?
d. Oxygen atoms are shown
in both versions. How many
oxygen atoms are in Odor 4?
Compare the 2 versions of Odor 5 shown below a. Using the full atom
and answer the related questions on the right
version, circle the parts
that are also visible in
the shorthand version
b. Using the shorthand
version, fill in the
missing atoms that are
shown on the full atom
version.
Describe and illustrate how carbon atoms are
represented in the shorthand version
How many carbon atoms are in
odor 6?
Take a look at odor 6.
Circle all the
unwritten carbon
atoms.
Actual Smell
Odor 4
Odor 5
.
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Smell Lab –Receptors in Action , HASPI Medical Chemistry Lab
Odor 6
Part C: Terpenes
Molecule
Odor 7
Odor 8
Odor 9
Smell Prediction
1. The odors 7, 8 & 9 comprise the family of
molecules called terpenes. Identify the common
pattern within the family of terpenes and draw
it on the right.
2. Compare odor 7 & 8. Explain why they might
have similar smells.
There are a lot of different ways to put together a set of atoms. Two compounds with the same
molecular formula (all of the same atoms), but with different structures are called isomers. Odor 7
and Odor 8 are sterioisomers, meaning they are put together the same, but in this situation they are
mirror images of each other. Just like your right hand and left hand fit only in the glove that was made
for that hand, these sterioisomers react with your olfactory receptors differently.
Can you find all 10 of the carbon
atoms in Odor 7 and Odor 9 ?
Three of them are easy to find, but
can you find the other seven which
are the not drawn in on the shorthand version. Circle all 10 carbon
atoms for each molecule.
Actual Smell
Odor 7
Odor 8
Odor 9
Part D: Alcohols
Molecule
Odor 10
Odor 11
Odor 12
Smell Prediction
1. The odors 10, 11 & 12 comprise the family of
molecules called alcohols. Identify the common
pattern within the family of alcohols and draw
it to the right.
Smell Lab –Receptors in Action , HASPI Medical Chemistry Lab
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2. The short-hand and full atom version of a. Refer to the full atom
Odor 10 is shown. Answer the following version for Odor 10.
questions relating to the structures
How many lines are
connected to each
carbon atom?
b. How many lines are
connected to each
hydrogen atom?
c. How many lines are
connected to each
Hydrogen atom?
3. Molecular Structures would not exist without the
valence electrons that are available for bonding.
Draw the lewis dot structures for carbon, hydrogen
and oxygen
4. How are unpaired electrons in a lewis dot
structure similar to the lines that are shown to
connect 2 atoms in a molecular structure?
C
H
O
5. The atoms that comprise the molecular
structures in this lab are carbon, hydrogen and
oxygen atoms. They are all non-metals. What type
of bond holds the atoms together?
6. Shown to the right are two short-hand
versions of Odor 10, the one on the right
includes all of the hydrogen atoms. Look at
the arrows pointing at two different carbon
atoms in the representation on the left.
Observe in the representation on the right that
each of those carbon atoms has a different
amount of hydrogen atoms bonded to it. Look
for a pattern and provide a reason why you
think this happens?
Actual Smell
Odor 10
Odor 11
Odor 12
Part E: Ketones
Molecule
Odor 13
Odor 14
H3 C
O
Odor 15
CH 3
O
O
O
CH 3
HO
H3 C
CH2
Smell Prediction
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CH3
Smell Lab –Receptors in Action , HASPI Medical Chemistry Lab
H3C
CH 2
1. The odors 13, 14 & 15 comprise the family of
molecules called ketones. Identify the common
pattern within the family of ketones and draw
it to the right.
2. Circle all of the carbon atoms in Odor 13.
How many carbon atoms does it have?
How many oxygen atoms does it have?
How many hydrogen atoms does it have?
What is the formula for odor 13?
3. Draw the full atom version of odor 13 in the
space to the right. Refer back to your previous
work for help.
4. Look at odor 14 and determine how many
carbon atoms need hydrogen atoms and draw
them in on the structure on the right.
Actual Smell
Smell 13
Smell 14
Smell 15
Post Lab Questions
Look at this molecule of caffeine
How many carbon
atoms are in caffeine?
How many oxygen
atoms are in caffeine?
How many hydrogen
atoms are in caffeine?
What is the formula for
caffeine?
Draw the Lewis Dot Structure for N and S
N
How many bonds would you expect each atom N=
to form?
Take a look at these four
Do they all have the same atoms?
molecules:
S
S=
What term would you use to
describe these?
What is the formula of these
molecules?
Smell Lab –Receptors in Action , HASPI Medical Chemistry Lab
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References & Images
Adapted from Sensible Smells Lab – Andro Rios, Socrates Project, UCSD
http://www.doctorbenjamin.com/pharm/pharm.htm
http://microbiology2009.wikispaces.com/Histamines--What+They+Do+%26+What+AntiHistamines+Do+to+Stop+Them
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Smell Lab –Receptors in Action , HASPI Medical Chemistry Lab