Ionotropic Metabotropic Receptors Lesson 12 Membrane Proteins Ionophores
Ionotropic & Metabotropic Receptors Lesson 12
Membrane Proteins: Ionophores Ion Channels n Non-gated l always open n Gated l chemically-gated l electrically-gated l mechanically-gated ~ n
Chemically-Gated Channels Ligand-Receptor binding n Ligand l neurotransmitters l drugs n Receptor proteins l ligand binds to multiple receptors l receptor subtypes l specificity ~ n
Ligand-Receptors Binding site l specific point of ligand & receptor n Affinity l attraction l physical & electrical fit n NT or drug binds to receptor l or activity of neuron l excite or inhibit n Drugs mimic or block NT message ~ n
Lock & Key Model n NT binds to receptor l NT = key l Receptor = lock Receptor changes shape n Excitation or Inhibition? l Determined by nature of receptor n NOT NT ~ n
Receptor Subtypes Specificity n Same NT l Binds to many receptor subtypes l Produce different effects l EPSP or IPSP n All NT systems l Several subtypes each l Drug side effects ~ n
n ligand binds to receptor l activation: EPSP or IPSP NT Receptor A ~
n Same NT can bind to different -R l different part of NT ~ NT Receptor A Receptor B
n Same NT can bind to different -R l different part of NT ~ NT Receptor A Receptor B
n Same NT can bind to different -R l different part of NT ~ NT Receptor A Receptor B
Ionotropic receptors Ligand-gated channels l Ion channels n NT directly controls channel l fast action l transient ~ n
Metabotropic Receptors Requires energy l GTP l Neuromodulation n G protein-gated Ion Channels l Receptor indirectly controls channel l relatively fast, but slower than ionotropic ~ n
G protein-gated Ion Channels R G GDP
G protein-gated Ion Channels R G GTP
G protein-gated Ion Channels R G GTP Pore
Metabotropic receptors: 2 d messenger systems l Effects relatively slow l long-lasting l Signal amplification n Effects l Control channel l Alter properties of receptors l regulation of gene expression ~ n
2 d Messenger Systems n Signal amplification l 1 NT activate enzyme l ATP 1000 s c. AMP 10, 000 s l c. AMP 10, 000 s phosphates ~
2 d Messenger Systems n n n External signal l NT = 1 st messenger Membrane-associated components l Receptor l Transducer l Primary effector Intracellular l 2 d messenger l Secondary effector ~ external signal: nt Receptor transducer primary effector 2 d messenger secondary effector
2 d Messenger Systems Primary Effector Enzyme R G GTP * GDP Secondary Effector
2 d Messenger Systems Primary Effector Enzyme R G GTP Secondary Effector
2 d Messenger Systems Primary Effector Enzyme R G GTP ATP c. AMP Secondary Effector
2 d Messenger Systems Primary Effector Enzyme R G GTP ATP c. AMP Secondary Effector P
2 d Messenger Systems Primary Effector Enzyme R G GTP ATP P c. AMP Secondary Effector Pore
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