Download APDC Unit VI CSignalEndoc

CH 5*, 31*, 32*
LO 4.9
1. Why do you communicate?
2. How do you communicate?
3. How do you think cells communicate?
4. Do you think bacteria can communicate? Explain.
1. Compare the structure & function of these
receptor proteins: GPCR, tyrosine kinase
and ligand-gated ion channels.
2. What is a second messenger? What are
some examples of these molecules?
3. What are the possible responses to signal
transduction in a cell?
CHAPTER 5
 The 3 stages of cell communication: reception, transduction, and
response.
 How G-protein-coupled receptors receive signals and start
transduction.
 How receptor tyrosine kinase receive cell signals and start
transduction.
 How a cell signal is amplified by a phosphorylation cascade.
 How a cell response in the nucleus turns on genes while in the
cytoplasm it activates enzymes.
 What apoptosis means and why it is important to normal
functioning of multicellular organisms.
 Prokaryotes!
 All types!
(but in different ways)
Bonnie Bassler on How Bacteria “Talk”
https://www.ted.com/talks/bonnie_bassler_on_how_
bacteria_communicate/transcript?language=en
18:14
1. Why are scientists studying how bacteria (and not just
human cells) communicate?
2. What is quorum sensing?
3. Describe how Vibrio fischeri use quorum sensing in
squid.
4. According to Bonnie Bassler (Princeton University),
what are scientists hoping to use as the next class of
antibiotics?
Animal cells communicate
by:
 Direct contact (gap junctions)
 Secreting local regulators
(growth factors,
neurotransmitters)
 Long distance (hormones)
LOCAL VS LONG DISTANCE SIGNALING
Local regulators – affect only nearby cells
 Neurotransmitters released from neurons
 Direct Contact – between immune cells
Hormones – affect distant cells
 Endocrine signaling – chemicals released
into blood and carried throughout body
 Must have the correct receptors
 Either inside cell or along cell membrane
1. Reception: Detection of a signal molecule (ligand)
coming from outside the cell
2. Transduction: Convert signal to a form that can bring
about a cellular response
3. Response: Cellular response to the signal molecule
 Binding between signal molecule (ligand) +
receptor is highly specific.
 Types of Receptors:
a) Plasma membrane receptor

water-soluble ligands
b) Intracellular receptors (cytoplasm, nucleus)

hydrophobic or small ligands

Eg. testosterone or nitric oxide (NO)

Ligand binds to receptor protein  protein
changes SHAPE  initiates transduction signal
G-Protein
Coupled
Tyrosine Kinase
Receptor (GPCR)
Ligand-Gated
Ion Channels
G-Protein Coupled
Receptor (GPCR)
7 transmembrane
segments in
membrane
G protein + GTP
activates enzyme
 cell response
Tyrosine Kinase
Ligand-Gated Ion
Channels
G-Protein
Coupled
Tyrosine Kinase
Receptor (GPCR)
Attaches (P) to
tyrosine
Activate multiple
cellular responses
at once
Ligand-Gated
Ion Channels
G-Protein
Coupled
Tyrosine Kinase
Receptor (GPCR)
Ligand-Gated
Ion Channels
Signal on receptor
changes shape
Regulate flow of
specific ions
(Ca2+, Na+)
G-Protein Coupled
Receptor (GPCR)
Tyrosine Kinase
Ligand-Gated Ion
Channels
7 transmembrane
segments in
membrane
Attaches (P) to
tyrosine
Signal on receptor
changes shape
G protein + GTP
activates enzyme
 cell response
Activate multiple
cellular responses
at once
Regulate flow of
specific ions
(Ca2+, Na+)
Cascades of molecular interactions relay
signals from receptors  target molecules
Protein kinase: enzyme that phosphorylates
and activates proteins at next level
Phosphorylation cascade: enhance and
amplify signal
small, nonprotein molecules/ions that can relay
signal inside cell
Eg. cyclic AMP (cAMP), calcium ions
(Ca2+), inositol triphosphate (IP3)
 cAMP = cyclic adenosine monophosphate
 GPCR  adenylyl cyclase (convert ATP 
cAMP)  activate protein kinase A

Regulate protein synthesis
by turning on/off genes in
nucleus (gene expression)

Regulate activity of
proteins in cytoplasm
Cytoplasm Response
Response may
regulate activities
Ex: epinephrine
signals breakdown
of glycogen to
glucose
Notice the signal
amplification!
Nuclear Response
Signal may trigger
products to be made
Ex: growth factor signals
DNA to make certain
proteins needed for growth
(transcription - ?)
(traits - ?)
Specificity of Signals
The type of proteins a cell has determine which
signals it responds to and how it responds
 Positive feedback:
Oxytocin &
childbirth
 Negative feedback:
Insulin/Glucagon &
blood-glucose
 Lipid Hormone
Testosterone
 also good example of
different effects of same
hormone
 Protein Hormone Insulin
 Also good example of
effect if goes wrong –
diabetes
 What sort of communication happens in this system?
 What types of cells are involved? Who do they “talk”
to?
 T-cells require self & non-self copntact
 Antigen = the part they recognize as foreign
 Il-1 7 IL-2 used to help activate other cells
 What type of communication takes place here?
 Where does the “talking” take place?
 Neurotransmitters released into synaptic cleft…
cause channels to open which passes along the
“message”
 What happens when part of the system goes wrong?
 Which can get through membrane easily?
 Which will deliver message faster?
Evolutionary Link
These pathways are similar among all types of cells, even
among very different organisms (including bacteria, yeast,
plants, and animals)
What does this tell us about these pathways?
Why would they have been so important that they evolved so
early?
http://apbiomaedahs.weebly.com/3d-cell-communication-
and-signal-transduction.html
http://learn.genetics.utah.edu/content/cells/cell
com/
Examples:
 Diabetes
 Cholera
 Autoimmune disease
 Cancer
 Neurotoxins, poisons, pesticides
 Drugs (anesthetics, antihistamines, blood pressure meds)
 Toxin modifies G-protein
 Disease acquired by
drinking contaminated
water (w/human feces)
 Bacteria (Vibrio cholerae)
colonizes lining of small
intestine and produces
toxin
involved in regulating salt &
water secretion
 G protein stuck in active
form  intestinal cells
secrete salts, water
 Infected person develops
profuse diarrhea and could
die from loss of water and
salts
 Used as treatment for erectile dysfunction
 Inhibits hydrolysis of cGMP  GMP
 Prolongs signal to relax smooth muscle in
artery walls; increase blood flow to penis
VIAGRA INHIBITS CGMP BREAKDOWN
 Cell is dismantled and digested
 Triggered by signals that activate cascade of
“suicide” proteins (caspase)
 Why?
 Protect neighboring cells from damage
 Animal development & maintenance
 May be involved in some diseases
(Parkinson’s, Alzheimer’s)
Left: Normal WBC
Right: WBC undergoing apoptosis – shrinking and forming lobes
(“blebs”)
1. What type of behavior in animals might be
triggered by cold temperatures?
2. What type of behaviors might be triggered in hot
temperatures?
3. List 2 examples of negative feedback. List 2
examples of positive feedback.
4. What is the main type of chemical messenger in
the endocrine system? The nervous system?
Compare & Contrast the nervous system with
the endocrine system. (focus on the effects on
the body
Define neurosecretory cell. What is its function?
Give an example of positive and negative
feedback in the endocrine system. How do they
function?
1. Compare peptide hormones to steroids.
2. Explain how insulin and glucagon work to
regulate blood sugar levels.
3. Which glands and hormones respond when
your body is under stress?
A hormone called ecdysteroid regulates the timing of metamorphosis in this anise swallowtail butterfly.
 Tropism- any growth response that results in plant organs curving
TOWARD or AWAY from stimuli
 Phototropism- the growth of a plant organ TOWARD light or AWAY from
it
 Important plant hormones:
 Auxin- simulate cell elongation phototropism & gravitropism (high
concentrations=herbicide)
 Cytokinins-cell division (cytokinesis) & differentiation
 Gibberellins-stem elongation, leaf growth, germination, flowering, fruit
development
 Abscisic Acid- slows growth; closes stomata during water stress, promote
dormancy
 Ethylene-promote fruit ripening (positive feedback!); involved in apoptosis
(shed leaves, death of annuals)
1. Drought (water deficit)
 Close stoma
 Release abscisic acid to keep stoma closed
 Inhibit growth
 Roll leavesreduce SA & transpiration
 Deeper roots
2. Flooding (O2 deprivation)
 Release ethyleneroot cell death air tubes formed to provide
O2 to submerged roots
A hormone called ecdysteroid regulates the timing of metamorphosis in this anise swallowtail butterfly.
 Two ways hormones affect target organs.
 The secretion, target, action, and regulation of at least 3
hormones.
 An illustration of both positive and negative feedback
in the regulation of homeostasis by hormones.

Local regulators – affect only nearby cells
 Paracrine signaling – cells release
chemicals to nearby cells
 Neurotransmitters released from
neurons

Hormones – affect distant cells
 Endocrine signaling – chemicals
released into blood and carried
throughout body
Cells can also pass
messages directly
- Gap junctions
- Plasmodesmata
- “ID tag” recognition
 Endocrine System = Hormone-secreting cells
+ Tissues
 Endocrine glands: ductless, secrete hormones
directly into body fluids
 Hormones: chemical signals that cause a
response in target cells (receptor proteins for
specific hormones)
 Affects 1 tissue, a few, or most tissues in body
 Or affect other endocrine glands (tropic
hormones)
 Regulation by Positive & Negative Feedback
Pheromones
Hormones
Local
Regulators
Chemical
Chemical
signal from
Chemical
signal from 1
endocrine
signal from one
individual to
gland through
cell to an
another
blood to target adjacent cell
individual
cell
Eg. cytokines,
Eg. peptide,
Eg. ant trail; sex
growth factors,
steroid
pheromones
nitric oxide
hormones
(NO)
https://www.youtube.com/watch?v=-S_vQZDH9hY
Peptide
Steroid
 Water-soluble
 Lipid-soluble
 Bind to receptors on
 Enters cell & binds to
plasma membrane &
triggers signal
transduction pathway
 Affects protein activity
already present in cell
 Rapid response
 Short-lived
 Eg. oxytocin, insulin,
epinephrine
intracellular receptors
 Causes change in gene
expression (protein
synthesis)
 Slower response
 Longer life
 Eg. androgens
(testosterone), estrogen,
progesterone, cortisol
1.Liver cells break
2.Blood vessels to
down glycogen and
skeletal muscles
release glucose
dilate
3.Blood vessels
to intestines
constrict
Master Glands
Hypothalamus
Pituitary Gland
Master Glands
Hypothalamus
• Receives info from nerves and brain
• Initiates endocrine signals
Posterior pituitary gland:
• Oxytocin: contract uterine muscles, eject milk
in nursing
Pituitary Gland
• Antidiuretic Hormone (ADH): promote H2O
retention by kidneys
Anterior pituitary gland:
• Follicle-stimulating hormone (FSH):
development of ovarian follicles (eggs);
promote sperm production
• Luteinizing hormone (LH): trigger ovulation;
stimulate testosterone production in testes
HYPOTHALAMUS
POSTERIOR PITUITARY
HYPOTHALAMUS
ANTERIOR PITUITARY
 Negative feedback systems:
• Thyroid hormones
• Blood Ca2+ levels
• Blood glucose levels
 Positive feedback system:
• Oxytocin (birthing process;
release of milk/suckling)
INSULIN & GLUCAGON
High blood
glucose
Liver breaks down
glycogen and
releases glucose
into blood
Insulin released from
pancreas
Glucagon released
from pancreas
Body cells take up glucose
Liver stores glucose as
glycogen
Blood
glucose
drops
 Type I diabetes (10%):deficiency of insulin
 Insulin-dependent
 Autoimmune disorder  beta cells of
pancreas destroyed
 Type II diabetes (90%): failure of target cells
to respond to insulin
 Non-insulin dependent
 Insulin produced  cells don’t respond
(defect in insulin receptor or response
pathway)
 Risk factors: obesity, lack of exercise
Thyroid Gland
Hypothalamus
Graves’ Disease:
 Autoimmune disorder
TRH
 Antibodies bind to TSH
receptor
Anterior
pituitary
 Hyperthyroidism
 High temp, sweating,
weight loss, high BP
TSH
Thyroid
T3
T4
STRESS AND THE ADRENAL GLAND
 Legally prescribed to treat hormone
deficiency, loss of muscle mass (cancer, AIDS)
 Used to enhance performance and improve
physical appearance
SOURCE: WWW.DRUGABUSE.GOV/INFOFACTS/STEROIDS.HTML
 aggression
 extreme mood swings
 liver damage
 jaundice
 fluid retention
 high blood pressure
 increases in LDL (“bad”
cholesterol)
 decreases in HDL (“good”
cholesterol)
 renal failure
 severe acne
 For men—shrinking of the testicles,
reduced sperm count, infertility, baldness,
development of breasts, increased risk
for prostate cancer
 For women—growth of facial hair, male-
pattern baldness, changes in or cessation
of the menstrual cycle, enlargement of the
clitoris, deepened voice
 For adolescents—stunted growth due to
premature skeletal maturation and
accelerated puberty changes; risk of not
reaching expected height if AAS is taken
before the typical adolescent growth
spurt
 In addition, people who inject AAS run
the added risk of contracting or
transmitting HIV/AIDS or hepatitis.
 What determines whether a signal will bind
to a membrane protein or an intracellular
protein?
 Membrane signals – cannot get through
 Large - polar - ionic
 Intracellular signals – can get through
 Hydrophobic - small
 Which types of cells communicate this way?
 Most of them!
 bacteria – yeast (fungi) – plants - animals
 Briefly explain the role of each numbered
step in regulating target gene expression.
(2013 #8)