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RECEPTORS & SIGNALLING (SIGNALLING PATHWAYS (JAK STAT (CYTOKINE…

- - - - RECEPTOR & LIGAND BINDING IS VERY SPECIFIC
      - DIFF. RECEPTORS CAN RESPOND TO SAME LIGAND
      - CONFORMATIONAL CHANGE IN RECEPTOR INITIATES SIGNAL TRANSDUCTION
      - RECEPTORS ARE FOUND INTRACELLULARLY & INTERCELLULARLY
        
        INTERCELLULAR RECEPTORS
        
        TRANSMEMBRANE RECEPTORS
        
        TYROSINE KINASES RECEPTORS
        
        ATTACHED PHOSPHATES TO TYROSINES
        
        KINASE
        
        ENZYME THAT TRANSFERS PHOSPHATE FROM HIGH ENERGY MOLECULE TO SPECIFIC SUBSTRATE= PHOSPHORYLATION
        
        E.G. MOST RECEPTORS FOR GROWTH FACTORS & INSULIN
        
        ION CHANNEL RECEPTORS
        
        ACTS AS GATE
        
        WHEN LIGAND BINDS TO RECEPTOR, A CHANNEL OPENS ALLOWING THE ENTRANCE/ EXIT OF SPECIFIC IONS
        
        E.G. MUSCLE CONTRACTIONS & NEURON COMMUNICATION
        
        G- PROTEIN LINKED RECEPTORS(GPCRs)
        
        FUNCTIONS WITH HELP OF G- PROTEIN
        
        G PROTEIN ACTS ON ON/OFF SWITCH; IF GDP IS ATTACHED TO G PROTEIN THEN THE G PROTEIN IS INACTIVE
        
        LARGEST FAMILY OF CELL SURFACE RECEPTORS
        
        RECEPTORS FOR: EPINEPHRINE, SEROTONINE(NEUROTRANS) & GLUCAGON
    - - CONVERSION OF PHYSICAL/CHEMICAL SIGNAL ON CELL SURFACE INTO SPECIFIC CELLULAR MESSAGE
      - RECEPTOR ACTIVATES PROTEIN WHICH ACTIVATES ANOTHER........ PRDOUCING CELL RESPONSE ( DOMINO EFFECT)
      - IN EACH STEP SIGNAL IS CONVERTED INTO A DIFF. FORM
      - SIGNAL IS RELAYED VIA RELAY PROTEINS
        
        PROTEIN KINASES & PHOSPHATES
        
        THESE TWO ACT TOGETHER TO SWITCH FUNCTION OF PROTEIN ON & OFF
        
        GTPASE SWITCH PROTEINS
        
        ACTIVE WHEN BOUND TO GTP BUT INACTIVE WHEN BOUND TO GDP
        
        GUANINE-NUCLEOTIDE EXCHANGE FACTOR (GEFs) PROMOTE SWITCH BTW GDP TO GTP & ACTIVATES GTPASEs
        
        GTPASE ACTIVATING PROTEIN (GAPs) STIMULATE RATE OF GTP HYDROLYSIS TO GDP & INACTIVATE GTPASEs
      - NO. OF 2ND MESSENGERS LESSER THAN 1ST MESSENGERS THIS IS FOR:
        
        GREATER COORDINATION & REGULATION
        
        AMPLIFICATION OF SIGNAL
        
        THIS IS CARRIED OUT BY ENZYME CASCADES
        
        [+] ACTIVATED MOLECULES
        
        SAME SIGNALLING PATHWAY HAS DIFF. RESPONSE IN DIFF. CELLS (ECONOMICAL)
        
        2ND MESSENGERS ARE IONS THAT DIFFUSE TO TARGET PROTEINS
    - - SPECIFICITY: ONE SIGNAL MOLECULE CAN TRIGGER MULTIPLE RECEPTORS & BRING ABOUT VARIOUS RESPONSES
      - A SIGNAL CAN TRIGGER AN ACTIVATOR/INHIBITOR
      - RESPONSES INCLU. :
        
        CYTOPLASMIC ACTIVITIES
        
        NUCLEAR TRANSCRIPTION
        
        METABOLISM REGULATION
  - - - ENZYMES
      - 2ND MESSENGERS
    - - DETECTS SIGNAL
    - - MEMBRANE PERMEABLE
        
        SMALL, HYDROPHOBIC LIGANDS THAT BIND TO INTRACELLULAR RECEPTORS
        
        TARGET & REGULATE INTRACELL. ENZYMES
        
        E.G. STEROID & THYROID HORMONES
      - MEMBRANE IMPERMEABLE
        
        BIND TO RECEPTORS ON MEMBRANE SURFACE
        
        E.G. PROTEINS & NEUROTRANSMITTERS
- - - - JUXTACRINE
    - - AUTOCRINE, PARACRINE & NEURAL
- - - - CAFFEINE
      - PDE INHIBITORS
      - CHOLERA TOXIN
      - PERTUSSIS TOXIN
    - - Gi PROTEIN
      - PDE
  - - - INNATE & ADAPTIVE IMMUNITY
      - INFLAMMATION
      - STRESS RESPONSES
      - LYMPHOCYTE DEV.
- - - - DILATE & CONSTRICT BV & BRONCHI
      - PROMOTE FEVER & PAIN
      - REGULATE INFLAMM.
    - - CONSTRICTION BV
      - AGGREGATES PLATELETS (CLOT)
    - - WHITE CELLS TO AREA
      - [+] VASCULAR PERMEABILITY
      - AGGREGATE PLATELETS (CLOT)