HORMONES AND CELL SIGNALLING

Transcription

1 HORMONES AND CELL SIGNALLING

2 TYPES OF CELL JUNCTIONS

3 CHEMICAL SIGNALS AND MODES OF ACTION Endocrine system produces chemical messages = hormones that are transported from endocrine gland to target cell in the blood Hormones = chemical signals that travel throughout the body Local regulators act on near by cells Pheromones communicate between different individuals These play a role in animal reproduction

4 CLASSES OF HORMONES Protein-based hormones polypeptides 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

5 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

6 ACTION OF LIPID (STEROID) HORMONES target cell cytoplasm S 2 steroid hormone S 1 cross cell membrane S protein carrier blood becomes transcription factor 3 S binds to receptor protein 5 mrna read by ribosome DNA 4 nucleus plasma membrane mrna 6 7 protein protein secreted ex: secreted protein = growth factor (hair, bone, muscle, gametes)

7 ACTION OF PROTEIN HORMONES signal-transduction pathway protein hormone 1 P signal plasma membrane binds to receptor protein activates G-protein activates enzyme receptor protein activates cytoplasmic signal cytoplasm GTP ATP activates enzyme activates enzyme camp acts as 2 messenger transduction 2 secondary messenger system target cell produces an action 3 response

8 POLAR AND NON-POLAR HORMONES

9 HORMONE RECEPTOR COMPLEX

10 EX: ACTION OF EPINEPHRINE (ADRENALINE) signal epinephrine 1 adrenal gland receptor protein in cell membrane activates GTP GTP activates G protein 2 GDP 3 ATP activates adenylyl cyclase camp 4 activates protein kinase-a transduction 5 cytoplasm activates phosphorylase kinase activates glycogen phosphorylase released to blood liver cell glycogen 6 glucose 7 response

11 DIFFERENT EFFECTS OF A CHEMICAL SIGNAL A single type of signal molecule can produce different responses in different target cells May be due to different receptors May be due to differences within the signal transduction pathway of the target cell

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13 BENEFITS OF A 2 MESSENGER SYSTEM signal receptor protein 1 Activated adenylyl cyclase 2 amplification Not yet activated 4 amplification Amplification! GTP 3 G protein amplification 6 5 amplification camp protein kinase Cascade multiplier! 7 amplification enzyme FAST response! product

14 MAINTAINING HOMEOSTASIS hormone 1 gland lowers body condition high specific body condition low raises body condition gland hormone 2 Negative Feedback Model

15 Nervous System Control CONTROLLING BODY TEMPERATURE Feedback nerve signals hypothalamus sweat dilates surface blood vessels high body temperature (37 C) low hypothalamus constricts surface shiver blood vessels nerve signals

16 Endocrine System Control REGULATION OF BLOOD SUGAR insulin islets of Langerhans beta islet cells Feedback pancreas body cells take up sugar from blood liver stores glycogen reduces appetite high blood sugar level (90mg/100ml) low liver triggers hunger liver releases glucose pancreas liver glucagon islets of Langerhans alpha islet cells

17 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.

18 NERVOUS & ENDOCRINE SYSTEMS LINKED Hypothalamus = 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 range of tropic hormones regulating other glands in body pituitary posterior hypothalamus anterior

19 HOMOLOGY IN HORMONES What does this tell you about these hormones? prolactin mammals birds fish amphibians milk production fat metabolism salt & water balance metamorphosis & maturation

20 SIGNAL TRANSDUCTION MODELING Create 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