Signal Transduction Lecture 1 : Basics Flashcards
Compare Endocrine, paracrine, autocrine signalling and Plasma membrane attach signalling
Endocrine= from gland into the blood circulation to distant target organ
Paracrine = goes to the synapse to act on adjacent cells
Autocrine = Target cell is the secreting cell (growth factors)
Plasma membrane attach signalling = the cell next to target cell has the ligand still attached.
(T cell activation of B cell antigen presenting)
What is a hormone
Extracellular signals that are secreted by cells that then diffuse/ circulate to specific target cell=> that has a receptor.
What are the 5 major stages of Signal Transduction
- Extracellular signal 2.Received by plasma membrane receptor
- Amplification (small initial signal-> big response)
- Transduction
- Responses
What are the two reasons why signal transduction is important for medicine
It helps to maintain homeostasis, receiving sensory input, many medicines target the cell receptors to control signal transduction processes.
What is transduction
The process of chemical messengers relaying an initial signal from outside to inside which gets amplified and induces response (s)
What is the lock and key analogy and how does it link to conformational change
Hormones/ligands have specific receptors due to specific amino acid chains. Once it is bound, the ligand causes a conformational change that causes the intracellular portion to bind to things in the cells. This allows signalling to occur without hormone passing through the cell membrane.
What is the difference of Antagonist and Agonist
Agonists :
Produce a maximal response for a given tissue.
Whereas Antagonist: produces no visible response and blocks the effects of agonist.
What is the similarity of Antagonist and Agonist and Partial agonist
Similarity: they are both molecules that bind to receptor in place of the ligand.
What is Partial agonist
They produce a response which is below the maximum for that tissue (as defined by the full agonist)
What are the two mechanisms of signal transduction common to many pathway
Second messengers and Phosphorylation cascades
What are the 3 classes of plasma membrane receptor
- G protein- coupled receptors (GPCR) - use g protein and 2nd messengers
- Receptor Tyrosine kinases (RTK) - use phosphorylation of tyrosines - phosphorylation cascade
- Ligand gated ion channel receptors
- ligands activate opening of ion channel (direct signalling)
What is a 2nd messenger
- Chemical signals not often embedded in the membrane.
- Diffuse intracellularly
- Produced following receptor activation in dose response relationship.
What are the advantages of a Multistep transduction pathway
- Signal is Amplified
- More points for coordination and regulation of cell response
Common 2nd messengers - need to recognise structures
Cyclic AMP, Cyclic GMP
Ca2+
IP3
DAG
How can the small number of 2nd messengers produce a large number of cellular responses
- Each tissue cell type has specific proteins that allow cells to detect and respond to different signals.
- One 2nd messenger can activate more than one response depending on what substrates present
- There can be cross talk between 2 receptors being activated-> inhibited or up regulated
- The same hormone/ligand can bind to different receptor which leads to different response
