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
Phosphorylation : What is the mechanism of action, range of action
Mech:
- Kinases transfer phosphate from ATP to protein.
- Acts as a molecular switch turning protein activity on or Off, depending on the molecule.
Range: Wide spread cellular mechanism- resulting in phosphorylation cascade.
What are the 3 amino acids phosphorylated
Tyrosine, serine and threonine
Dephosphorylation is done by what
Phosphatases which rapdily remove phosphates from proteins to reset the system
How does 2nd messenging result in amplification
One receptor can activate more than 1 2nd messenger. The number of activated products is much greater than in the preceding step. This allows the body to be sensitive to small amounts of hormone needed to produce response
Give examples of different physiological functions of cell surface receptors (the changes in chemicals result)
- activation or inhibition of proteins
- regulate gene transcription factors that directly control processes.
- pumps
- enzymes
- vision, taste, smell,
- neurotransmission
- cell development
