Signal : ligand, molecule that binds to specific site on another molecule

Eg : Hormones, Neurotransmitter, Growth Factor, Cytokines, Antigens

Concept of lock and Key, allow molecule of particular shape to trigger change in chemical activity

Receptor : G-protein coupled receptor, receptor tyrosine kinase, receptor guanylate cyclase, adenylate cyclase, phospholipase

G-protein

Eg : Cyclic AMP, Calcium, inositol triphosphate, nitric oxide, cyclic GMP, diacyglycerol

Eg ; Nitric oxide synthase, Guanylate cyclase, Calmodulin, Phosphodiesterase, CRE, CREB, Protein kinase, Protein Phosphatase

Altered metabolism, altered gene expression or Altered cell shape or motility

Fast

Slow

Ion Channel Linked

G-protein linked

Enzyme Linked

modified ATP >stimulate G protein receptor > activate G protein > activate enzyme in membrane plasma

enzyme convert ATP into cyclic AMP > activate protein kinase

protein kinase phosphorylate other protein

another enzyme can inactivate cAMP

example:

physiological effect:

soluble and highly reactive gas produced by natural chemical and physical reaction

small and diffusible through membrane plasma

function:

Nitric acid synthetase (NOS) synthesize NO from L-arginine to form L-citrulline and nitric oxide

NO diffuse out of blood vessel and enter muscle cell

NO bind with nitric acid receptor and convert GTP to cyclic GMP

cyclic GMP bind to protein kinase G

Extrinsic

Intrinsic

Merocrine

Holocrine

Apocrine