Intracellular Signalling Flashcards
What is a cellular response?
It is a change in metabolic activities by actions of secretion, release, changes in gene expression and sensory perception
What 4 factors act as extracellular signals?
1) Amino acids and their derivatives
2) Steroids
3) Prostaglandins
4) Proteins and peptides
The 5 different ways cells contact each other?
Endocrine - signal produced in one part of the body and transports via the blood to a target cell
Autocrine - signal acts on same cell that produces it
Paracrine - Signal acts on other cells very close to where its produced
Contact development - signal is apart of the cell and interacts directly with another cell
Neuronal - Electrical signal transmitted down cell and moves to a cell via synapse
What two things must receptors have?
High selectivity and high affinity
How do signals work?
They bind to receptors
How do cell surface receptors work?
They have a hydrophilic hormone. the binding of this hormone triggers a response
How do intracellular receptors work?
They have hydrophobic hormones which cross the plasma membrane and bind to the cytosol receptor to trigger and intracellular response
The direct activation of transcription factors?
Steroid hormones have a hormone, DNA and transcription factor binding domain
Binding of steroids induces conformational change allowing DNA binding and activation of target genes. sequence specific DNA binding domain allows activation
What are G-protein coupled receptors?
They are generated by enzymes
They are located in cell membranes and bind to substances to transmit signals to G-proteins
How to generate secondary messengers?
Activation of adenylyl cyclase by cAMP and activation of phospholipase C by IP3 and DAG allow for the generation of secondary messengers
6 steps to G-protein pathways?
1) first messenger
2) 7-transmembrane g-protein coupled receptors activated
3) Activation of G-alpha subunit by switch of GTP to GDP
4) Second messengers
5) inactivation of pathways via GTP hydrolysis
6) Degradation / reuptake of secondary messengers
What are G-proteins?
Guanine-nucleotide-binding proteins are used for cellular signalling
The G-a-subunit activates effector enzymes
How to dissociate and associate G-proteins?
They dissociate when GTP binds
The associate when GTP is hydrolysed by GTPase
GPCR signalling pathways to effector enzymes?
1) signal binds to receptor
2) G-protein associates with receptor
3) GTP/GDP exchange on G-protein
4) G-protein dissociates into alpha and beta subunits
5) Alpha subunits, with FTP, activate effector enzymes
6) Effector enzymes produce secondary messengers
7) GTP hydrolysis to GDP
8) G-protein complex associates and the signalling ends
How to activate cAMP dependant protein kinase and is then activated?
cAMP dependant protein kinase A is a tetrameric enzyme. (2 R and 2 C subunits)
cAMP binds to the regulatory subunit and tetramer dissociates
Catalytic monomers (C) become active enzymes
cAMP dependant protein kinase is then activated
