cell biology 7 Flashcards
what is signal transduction
process by which cells translate intracellular and extracellular signals to a cellular response
what does signal transduction regulate
- growth
- division
- differentiation
- behaviour
- cell death - apoptosis
what are the signalling pathways
- regulatory proteins
- chemical signals
what are the major steps in cell signalling
1) reception - signal molecule binds to a receptor protein
2) transduction - receptor activates one or more intracellular signalling pathways
3) response - one or more intracellular signalling proteins alters the activity of effector proteins
what is contact dependent signal transmission
- signalling cell has membrane bound signal molecule which attaches to attachment protein on target cell
what is autocrine cell signalling
- signal produced in cell and signals cell by exocytosis
what is paracrine cell signalling
- local mediator - short lived signals target cells from the signalling cell
what is synaptic cell signalling
- neurotransmitters move across synapse and to target cell receptors on the cell surface membrane
what is gap junction signalling
- small molecules move between gap junctions and passes on signals
what is endocrine cell signalling
- endocrine cell secretes hormones into bloodstream and they bind to receptors on the target cell
what are the types of signalling molecules
- Proteins
- Small peptides
- Amino acids
- Nucleotides
- Steroids
- Retinoids
- Fatty acid derivatives
- Dissolved gases; e.g. Nitric oxide and carbon monoxide
what types of cell transduction receptors are there
- cell surface receptors
- intracelular receptors
what are the 3 main classes of cell surface receptors in signal transduction
- ion channel receptors
- enzyme linked receptors
- G-protein coupled receptors
what are the common water soluble intracellular signals
Cyclic AMP (cAMP)
Cyclic GMP (cGMP)
Calcium
what are the common lipid intracellular signals
Diacylglycerol (DAG)
Phosphatidylinositol 4,5-bisphosphate (PIP2)
→ Released soluble Inositol 1,4,5-trisphosphate (IP3
what are the common intracellular enzyme modification signals
Protein Phosphorylation
GTP binding
what is protein phosphorylation regulated by
- kinase and phosphatases
- can lead to kinase cascades
what is GTP binding regulated by
- Guanine nucleotide exchange factors (GEFs)
- GTPase-activating proteins (GAPs)
what are the two main forms of GTP binding
- G proteins - Large, trimeric, relay signals from G-protein-coupled receptors
- Monomeric GTP-binding proteins - small, monomeric, relay signals from many cell-surface receptors
describe the hyperbolic response curve
- responses increases gradually
- plateau as the pathway is saturated
describe the sigmoidal response curve
- reduced response at low signal concentrations
describe the all or none curve
- cell switches between a low and high response
what is positive feedback
- activation of the signal causes an amplification of the signal
what is negative feedback
- activation of the signal reduces the signal
- cells can become desensitised to signal
how are G protein coupled receptors activated
- Guanine nucleotide exchange factor (GEF) to G-Proteins
- Remains active with bound signal → Multiple G-Protein activations
what do trimeric GTP-binding proteins do
- Acts on ion channels or enzymes
α Subunit - Binds GDP/GTP
- Membrane anchored
β Subunit - Becomes activated with γ
γ Subunit - Becomes activated with β
- Membrane anchored
what regulated the activity of G protein coupled receptors
- Activity of GPCRs are regulated by Phosphorylation by GRK and Arrestin binding
- Arrestin blocks G-Protein binding and promotes internalisation of GPCRs
- Some activated Arrestin molecules lead to separate signalling pathways
what stimulates cAMP production
- Many GPCRs stimulate cAMP production in hormone signalling - via Adenylyl Cyclase
