Endocrine & Cell Communication Part III: Hormonal Communication TEACHER NOTES needs coding
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You may want to print slide 39 for students so
they can complete the chart as an activity.
You will also want to have your set of
“Testesterone Manipulatives” handy.
Endocrine & Cell Communication Part III:
Hormonal Communication
• Enduring Understanding 3.D Cells communicate by
generating, transmitting and receiving chemical
signals.
• EK 3D2: Cells communicate with each other through
direct contact with other cells or from a distance via
chemical signaling
c. Signals released by one cell type can travel long distances
to target cells of another cell types.
1. Endocrine signals are produced by endocrine cells that
release signaling molecules, which are specific and can
travel long distances through the blood to reach all parts of
the body.
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The Process of Communication:
Signal-Transduction Pathway
Three stages of the SignalTransduction Pathway
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1. reception
2. transduction
3. response
Most cell communication involves three basic
steps, reception, transduction and response.
Today, we will see this signal transduction
pathway being initiated by hormones. We will
look at specific examples of how communication
is completed using this pathway.
The diagram shows a typical signal transduction
pathway. In our example today, we will consider
a ligand or signal molecule to be a hormone
produced by one of the endocrine glands we
discussed earlier.
Typical Signal Transduction Pathway
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The word transduce means to convert. A signal
transduction pathway “converts” the original
signal molecule into a cellular response. This
conversion requires several intermediate
messenger molecules (sometimes called “second
messengers”), so the signal is actually
“converted” or transduced several times, as
shown in the blue box above labeled
Transduction. The concept of signal transduction
pathways will be seen over and over again in AP
Biology and is certain to be on the exam.
Endocrine & Cell Communication Part III: Hormonal Communication TEACHER NOTES needs coding
Ligand = Chemical Messenger
• Three major classes of molecules function as
hormones in vertebrates (ligands)
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The hormones we consider today fall into three
main categories. Polypeptides, amines and
steroid hormones. The chemical make up of each
is different so it is not surprising that these
ligands impact cells very differently.
– Polypeptides (proteins and peptides)
– Amines derived from amino acids
– Steroid hormones
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Ligands
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LIGAND:
a molecule that
binds to a larger
molecule
The transduction pathway at the target cell
begins when the ligand binds to the receptor
forming a temporary ligand/receptor complex.
This stimulates transduction which leads to a
response from the cell. Have students cite some
examples of ligands.
Typical Signal Transduction Pathway
Emphasize that “Reception” begins when the
ligand establishes an IMF (intermolecular force)
or electrostatic attraction to a specific site on the
“Receptor”. Point out these IMFs are NOT
covalent chemical bonds but rather a strong
attraction that can be overcome with far less
energy than it would take to “break” an actual
covalent chemical bond.
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Phase 1: Reception
The target cell detects the ligand
• Membrane proteins
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–G-protein linked receptors
–Ion channel receptors
–Tyrosine Kinase
• Intracellular receptor
Receptor proteins may be found ON the cell or
IN the cell.
–Steroid hormone receptors
Type of Receptor : G-protein linke
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G protein linked receptors are located in the
membrane of the cell. When activated, the Gprotein linked receptor sets off a chain of events
inside the cell.
Endocrine & Cell Communication Part III: Hormonal Communication TEACHER NOTES needs coding
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Ion channel receptors, integral proteins found
within the cell membrane undergo a
Type of Receptor: Ion Channe
conformational (which is fancy for “shape”)
change when the ligand binds to the receptor.
Ions bear a charge and cannot enter the cell by
diffusion across the membrane. Instead, ions are
allowed to enter the cell when the ligand is
present and bound to the receptor. This allows
the influx of ions to be a regulated process.
Emphasize that any time charged particles (ions)
are transported a difference in electric potential
(as in potential energy) is established. This
electric potential is now available to do “work”!
We saw an example of ion channel
communication when we studied the
transmission of impulses from one neuron to the
next via neurotransmitters. The neurotransmitters
serve as ligand molecules allowing the influx of
sodium ions when the channel is open.
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Type of Receptor:
Intracellular Receptor
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Some receptors are located inside the cell and are
described as intracellular receptors. The receptor
for testosterone, for example is found inside the
cell.
Testosterone is a steroid hormone. Challenge
students to explain why steroid hormones have
intracellular receptors, while protein hormones
have extracellular receptors. (Steroids are lipids
and therefore easily diffuse through the
membrane and into the cell. Proteins will not
diffuse through the membrane due to both charge
and size, so they must bind with receptors on the
cell’s surface.)
Name three types of receptors in the signal
transduction pathway
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• G-protein-linked receptors
• Ion channel receptors
• Intracellular receptors
You should be able to give examples of
membrane bound receptors (G-protein linked and
ion channel receptors) as well as intracellular
receptors).
Endocrine & Cell Communication Part III: Hormonal Communication TEACHER NOTES needs coding
Ask students to explain what this image
represents – what is “transduction?”
Answers:
Signal transduction, any process by which a
biological cell converts one kind of signal or
stimulus into another OR A process by which a
transducer converts one type of energy to another
(chemical to electrical for example)
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Action of G-Protein Linked Receptor
Note that the GDP is replaced by higher energy
GTP in order for the process to continue.
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Transduction
• Binding changes the receptor
protein.
• Can set off a cascade reaction
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Response
• Set any of a variety of
cell activities in motion.
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–Activation of an enzyme
–Rearrangement of
cytoskeleton features
–Activation of a specific
gene
Endocrine & Cell Communication Part III: Hormonal Communication TEACHER NOTES needs coding
Recap
EXTRACELLULAR
FLUID
CYTOPLASM
Plasma membrane
1 Reception
Receptor
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Overview of cell signaling.
Signaling
molecule
Recap
EXTRACELLULAR
FLUID
1 Reception
CYTOPLASM
Plasma membrane
2 Transduction
Receptor
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Relay molecules in a signal transduction
pathway
Overview of cell signaling.
Signaling
molecule
Recap
EXTRACELLULAR
FLUID
1 Reception
CYTOPLASM
Plasma membrane
2 Transduction
3 Response
Receptor
Activation
of cellular
response
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Relay molecules in a signal transduction
pathway
Overview of cell signaling
Signaling
molecule
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Types of Receptors
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+
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Endocrine & Cell Communication Part III: Hormonal Communication TEACHER NOTES needs coding
Which is the receptor? G-Protein? Ligand?
A—Ligand or signal molecule such as
epinephrine
B—receptor molecule
C—relay molecule or second messenger, G
protein
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Which Is A Receptor Through Which Ions Would Pass?
Answer D—note the channel appearance
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Which Of These Acts As A Second Messenger?
D acts as the second messenger
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Water-soluble (hydrophilic)
Lipid-soluble (hydrophobic)
Polypeptides
Steroids
0.8 nm
Insulin
Cortisol
Amines
Hormones differ in structure and solubility.
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Epinephrine
Thyroxine
Cellular Response Pathways
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• Water- and lipid-soluble hormones differ in their
paths through a body
• Water-soluble hormones are secreted by exocytosis,
travel freely in the bloodstream, and bind to cellsurface receptors
• Lipid-soluble hormones diffuse across cell
membranes, travel in the bloodstream bound to
transport proteins, and diffuse through the
membrane of target cells
Protein/peptide hormones are released by
exocytosis, steroid hormones are able to leave
their secretory cells by way of diffusion. Once in
the blood stream, both travel to their target cells.
Upon arrival at the target cell, these two types of
hormones have different methods of
communicating with the target cells.
Endocrine & Cell Communication Part III: Hormonal Communication TEACHER NOTES needs coding
SECRETORY
CELL
Lipidsoluble
hormone
Watersoluble
hormone
VIA
BLOOD
Transport
protein
Signal receptor
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TARGET
CELL
Signal
receptor
NUCLEUS
(a)
(b)
Receptor location varies with hormone type.
Notice that the water soluble hormones, such as
epinephrine or insulin, bind with a membrane
bound receptor protein while the lipid soluble
hormone can pass directly through the membrane
of the target cell to dock with an intracellular
receptor.
SECRETORY
CELL
Lipidsoluble
hormone
Watersoluble
hormone
VIA
BLOOD
Signal receptor
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TARGET
CELL
Cytoplasmic
response
Transport
protein
OR
Gene
regulation
Receptor location varies with hormone type.
Signal
receptor
Cytoplasmic
response
Gene
regulation
NUCLEUS
(a)
(b)
Pathway for Water-Soluble Hormones
• Binding of a hormone to its receptor initiates a signa
transduction pathway leading to responses in the
cytoplasm, enzyme activation, or a change in gene
expression
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Pathway for Water-Soluble Hormones
The animation should play once you show this
slide.
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Specific Example
Notice the
presence of the
second messenger
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Click here
to view the
animation
Go through the numbered steps in this pathway
emphasizing the presence of a second messenger
and the amplification of the response inside the
cell. Click the blue tip of the arrow to link to a
video clip that explains the process of
amplification. (The link will only be active in
“presentation” mode). Once the video has been
viewed ask students to discuss the role of the
second messenger and the value of amplification.
Endocrine & Cell Communication Part III: Hormonal Communication TEACHER NOTES needs coding
Pathway for Lipid-Soluble Hormones
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• The response to a lipid-soluble hormone is usually a
change in gene expression
• Steroids, thyroid hormones, and the hormonal form o
vitamin D enter target cells and bind to protein
receptors in the cytoplasm or nucleus
• Protein-receptor complexes then act as transcription
factors in the nucleus, regulating transcription of
specific genes
Pathway for Lipid-Soluble Hormones
The animation should play once you show this
slide.
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Steroid Hormone Example: Testosterone
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Explain the pathway of a steroid hormone using
testosterone as an example. Pick a male student
with a moustache as your example and explain
how testosterone from the testes is secreted and
moves into the blood stream The testosterone
would move around the male’s body. However,
follicular cells have testosterone receptors and
respond to the presence of this hormone. Once
inside the follicle cell of the lip, the testosterone
stimulates the cell to produce keratin by “turning
on” the segment of DNA that codes for the
protein.”
In this case the protein produced could be
keratin.
Endocrine & Cell Communication Part III: Hormonal Communication TEACHER NOTES needs coding
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Model Steroid Hormone Action
using the Testosterone
Manipulative
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Have students take turns explaining the action of
a steroid hormone using the model provided. (Pig
hair from a paint brush can serve as the keratin
produced in this pathway). Hold students
accountable for the activity by having them write
a list of steps in the pathway from secretory cell
to keratin produced.
Compare protein and steroid hormones b
completing this T chart
Characteristic
Protein Hormone
Steroid Hormone
Speed of response
Primary biomolecule
composition
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Students should complete the chart on their own
or working with a partner.
Method of leaving secretory
cell
Location of receptor
Example
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Compare protein and steroid hormones b
completing this T chart
Characteristic
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Protein Hormone
Steroid Hormone
Speed of response
Rapid response, cascade
Response is slower, gene
expression
Primary biomolecule
composition
Amino acid
cholesterol
Method of leaving secretory Exocytosis
cell
Compare their responses to these suggested
responses.
diffusion
Location of receptor
Membrane bound
Intracellular
Example
Epinephrine
Testosterone
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Multiple Effects of Hormones
• The same hormone may have different effects on
target cells that have
– Different receptors for the hormone
– Different signal transduction pathways
The same hormone can cause different reactions
depending upon the cell it has targeted.
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Multiple Effects of Hormones
• The hormone epinephrine has multiple effects
in mediating the body’s response to short-term stres
• Epinephrine binds to receptors on the plasma
membrane of liver cells
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• This triggers the release of messenger molecules that
activate enzymes and result in the release of glucose
into the bloodstream
For example, epinephrine can be stimulatory is
some parts of the body and stimulatory in others.
Endocrine & Cell Communication Part III: Hormonal Communication TEACHER NOTES needs coding
Epinephrine inhibits the glycogen synthesizing
work of a liver cell while promoting the
breakdown of glycogen.
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Same receptors but different
Different receptors
intracellular proteins (not shown)
Different cellular
responses
Different cellular
responses
Epinephrine
Epinephrine
Epinephrine
β receptor
β receptor
α receptor
Glycogen
deposits
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Glycogen
breaks down
and glucose
is released
from cell.
(a) Liver cell
Vessel
dilates.
(b) Skeletal muscle
blood vessel
Vessel
constrict
One hormone, different effects.
(c) Intestinal blood
vessel
Did you know…
• One reason that kittens sleep so much is because a growth
hormone is released only during sleep.
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• The levels of two stress hormones, cortisol and
epinephrine which suppress the body's immune system,
will actually drop after a dose of laughter.
• Chocolate is associated with the release of serotonin, the
hormone that makes you feel relaxed, calm, and happy.
So are hugs.
Created by:
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Debra Richards
Coordinator of Secondary Science Programs
Bryan ISD
Bryan, TX
Just for fun!