HORMONES AND CELL SIGNALLING
TYPES OF CELL JUNCTIONS
CHEMICAL SIGNALS AND MODES OF ACTION
Endocrine system – produces chemical messages = hormones that are transported from endocrine gland to target cell in the bloodHormones = chemical signals that travel throughout the bodyLocal regulators act on near by cellsPheromones communicate between different individuals These play a role in animal reproduction
CLASSES OF HORMONES
Protein-based hormonespolypeptides small proteins: insulin, ADH
glycoproteins large proteins + carbohydrate: FSH, LH
amines modified amino acids: epinephrine, melatonin
Lipid-based hormones steroids modified cholesterol: sex hormones, aldosterone
insulin
HOW DO HORMONES ACT ON TARGET CELLS
Lipid-based hormones hydrophobic & lipid-soluble diffuse across cell membrane & enter cells bind to receptor proteins in cytoplasm & nucleus bind to DNA as transcription factors turn on genes
Protein-based hormones hydrophilic & not lipid soluble can’t diffuse across cell membrane bind to receptor proteins in cell membrane trigger secondary messenger pathway activate internal cellular response enzyme action, uptake or secretion of molecules…
nucleus
target cell
DNAmRNA
protein
blood
proteincarrier
S
S
S
S
ACTION OF LIPID (STEROID) HORMONES
binds to receptor protein
cytoplasm
becomes transcription factor
ex: secreted protein = growth factor (hair, bone, muscle, gametes)
2
4
6
cross cell membrane1
steroid hormone
mRNA read by ribosome5
plasma membrane
protein secreted7
3
ACTION OF PROTEIN HORMONES
activatesenzyme
activatesenzyme
activates enzyme
ATP
produces an action
P1
2
3
cytoplasm
receptorprotein
response
signal
secondarymessengersystem
signal-transduction pathway
acts as 2� messenger
target cell
plasma membrane
binds to receptor protein
proteinhormone
ATPactivatescytoplasmicsignal
cAMP
GTP
activatesG-protein
transduction
POLAR AND NON-POLAR HORMONES
HORMONE RECEPTOR COMPLEX
adrenal glandEX: ACTION OF EPINEPHRINE (ADRENALINE)
activatesprotein kinase-A
activatesglycogen phosphorylase
activatesadenylyl cyclase
epinephrine
liver cell
releasedto blood
1
2 5
receptorproteinin cell membrane
cytoplasm
6glycogen
activatesphosphorylase kinase
GTP
cAMP4
activatesG protein
ATP
glucose
activates GTP
3
signal
transduction
response7
GDP
DIFFERENT EFFECTS OF A CHEMICAL SIGNAL
A single type of signal molecule can produce different responses in different target cellsMay be due to different receptors May be due to differences within the signal transduction pathway of the target cell
BENEFITS OF A 2� MESSENGER SYSTEM
Amplification!
signal
receptor proteinActivated adenylyl cyclase
amplification
amplification
amplification
amplification
GTP G protein
product
enzyme
protein kinase
cAMP
Not yetactivated
1
2
4
35
6
7
FAST response!
amplification
Cascade multiplier!
MAINTAINING HOMEOSTASIS
high
low
hormone 1
lowersbody condition
hormone 2
gland
specific body condition
raisesbody condition gland
Negative FeedbackModel
CONTROLLING BODY TEMPERATURE
high
low
nerve signals
sweat
nerve signals
body temperature(37�C)
shiver
dilates surfaceblood vessels
constricts surfaceblood vessels
Nervous System Control Feedback
hypothalamus
hypothalamus
liver
pancreas
liver
REGULATION OF BLOOD SUGAR
blood sugar level(90mg/100ml)
insulin
body cells takeup sugar from blood
liver storesglycogen
reducesappetite
glucagon
pancreas
liver releasesglucose
triggershunger
high
low
FeedbackEndocrine System Controlislets of Langerhans beta islet cells
islets of Langerhansalpha islet cells
POSITIVE FEEDBACK AND HORMONES
Oxytocin induces contraction of the uterus during childbirth and causes mammary glands to eject milk during nursing.Oxytocin signaling in both cases exhibits positive feedback.
NERVOUS & ENDOCRINE SYSTEMS LINKEDHypothalamus = “master nerve control center” nervous system receives information from nerves around body about internal conditions releasing hormones: regulates release of hormones from pituitary
Pituitary gland = “master gland” endocrine system secretes broad rangeof “tropic” hormones regulating other glands in body
hypothalamus
pituitary
posterior
anterior
HOMOLOGY IN HORMONES
prolactin
mammals
milkproduction
birds
fatmetabolism
amphibians
metamorphosis& maturation
fish
salt &waterbalance
What does this tell you about these hormones?
SIGNAL TRANSDUCTION MODELINGCreate a model that demonstrate signal transduction.
The protein hormone glucagon that binds to a receptor in the plasma membrane with a cytoplasmic response through a G-protein & 2nd messenger & phosphorylation cascade (that leads to the breakdown glycogen to glucose).
Must Include: G-protein linked receptor, G protein, Adenylyl Cyclase, ATP & cAMP, multiple kinases, phosphates, glycogen phosphorylase, glycogen (& glucose)
Note: The final response is carried out by the phosphorylation the enzyme glycogen phosphorylase