Biological Signalling: General + Types of Signal Transducers Flashcards
(43 cards)
What are the 4 Characteristics of Signal Transduction Pathways:
- Specificity and Sensitivity
- Amplification
- Desensitization and Adaptation
- Integration
Signal transduction: Specificity
signal molecule fits the binding site on its complementary receptor
other signals do not fit
Increased specificity = ____ binding = ___ Kd
tight binding
low Kd
Additional features to increase specificity in cells?
- specific receptors depending onthe cell
Signal transduction: sensitivity: 3 factors
- high affinity of receptors for signal molecules
- cooperativity in ligand receptor interaction
- amplification of signal by enzyme cascades
What does a high affinity of receptors mean in terms of concentration of ligands needed and activation response?
- high affinity for receptors to bind means
- low concentration of ligand necessary to elicit a large activation response
Signal transduction: Amplification
- enzymes activate enzymes
- number of affected molecules increases geometrically in an enzyme cascade
Signal transduction: Desensitization / Adaptation
- receptor activation triggers feedback circuit
- that shuts off receptor or removes from cell surface
Protein kinases that phosphorylate and increase downstream protein kinases (kinase cascade) is an example of which signal transduction characteristic?
- amplification
How are kinase cascades decreased?
protein phosphorylase removes phosphate
this shuts down the kinase cascade until stimulus reaches below a threshold
Signal Transduction: Integration
- two signals have opposite effects on metabolic characteristic
- regulatory net outcome (input from both receptors) elicits the response
- unified response appropriate to needs of organism
Types of signal transductors:
- G protein coupled receptor
- receptor tyrosine kinase
- receptor guanylyl cyclase
- gated ion channel
- adhesion receptor
- nuclear receptor
G protein coupled receptor
- ligand binds receptor
- activates GTP binding protein
- regulates enzyme that generates secondary messenger
i. e. adrenaline receptor -> PKA
Receptor tyrosine kinase
- ligand binding activates tyrosine kinase
- autophosphorylation
- i.e. insulin receptor
Gated ion channel
- open/close channels in response to concentration of signal ligand or membrane potential
i. e. Ach receptor
Two types of neurotransmitters for ionotropic receptors:
- biogenic amines
- amino acids
Which biogenic amines give a positive effect to nerve transmission?
- acetyl choline
- nicotinic receptors
- muscarini c receptors (M1-5)
What is Ach and what does it do?
- main neurotransmitter for nerve-muscle (voluntary); CNS; parasympathetic (involuntary)
What do nicotinic receptors do?
- triggers Na+ and Ca+ inflow (down gradient)
- depolarize
- activation [nicotine]
Which biogenic amines give a negative effect to nerve transmission?
- Gamma-aminobutyric acid (GABA)
- a major inhibitory NT in the CNS
What do GABA receptors do?
- inhibit NT in CNS
- triggers influx of Cl- (recall Cl- is high outside)
- hyperpolarizing (cuz too negative inside)
- inactivation [tranquilizers, alcohol, barbiturates]
Which amino acid neurotransmitters for ionotropic receptors give a positive effect?
- glutamate
- AMPA, Kainate, NMDA, delta receptors
What does glutamate do?
major NT in CNS
What do the AMPA, Kainate, NMDA, delta receptors do?
- triggers Na+ and Ca2+ influx
- depolarize
- involved in learning, memory, plasticity
[antipsychotics, anti-schizophrenia]
