S&F; Cell Communication Flashcards
why do cells have to communicate?
they need to respond as a cell, and as part of a whole tissue (environment)
signals are often chemical (can also be light,taste,smell)
what are the two different types of secreted signals?
local signaling + long distance signaling
what is local signaling + examples
signals that act on nearby target cells
1. paracine; growth factors such as fibroblast growth factor (FGF1)
2. synaptic; neurotransmitters such as acetylcholine
what is long distance signaling + examples
signals acting from a distance
- hormones produced by specialised cells -circulatory system-> to act on specific cells
e.g. insulin from pancreatic beta cells -> insulin receptors -> cascade -> glucose uptake.
what are the three main steps of cell signalling?
reception; primary messenger/ligand binds to receptor -> changes its shape/chemical state
transduction, altered receptor activates another protein (g-protein/adenylyl cyclase), cause a relay of changes. each activated protein causes a series of changes.
response; cause one or more functions to occur in the cell.
what are the two main types of receptors?
intracellular receptors + membrane bound receptors
what are intracellular receptors
primary messenger = hydrophobic/small, lipid soluble can enter the cell.
least common method of signalling
e.g. testosterone, estrogen, progesterone, thyroid hormones
what are membrane bound cell surface receptors
primary messenger = hydrophillic/large
most common method of signalling
e.g. GPCR, ligand gated, tyrosine kinase
what are the features of GPCRS?
transmembrane proteins, pass the pm 7 times
nobel prize, 1/3 of modern drugs
many diff ligans, diverse functions (development, sensory reception)
g proteins; molecular switches which are either on/off depending on whether gdp or gtp is bound
how do gpcrs work?
- at rest, [receptor is unbound], and [G protein is bound to gdp]
- [[ligand binds receptor] binds to the G protein], GTP displaces GDP, [enzyme = inactive] –> conformational change
- [activated G protein dissociates from receptor.], [g protein activates enzyme]
- g protein has GTPase activity (GTP is hydrolysed to GDP and P) –> is released from enzyme, and everything goes back to normal ;D
featuer of ligand gates ion channels
contains a gate
binding on site causes a change in shape
this changing of shape causes channels to open/close
ions (Na, K, Ca, Cl) can pass through
how to ligand gates ions work
- at rest, ligand is unbound + gate is closed
- ligand binds, gate opens, specific ions can flow into the cell
- ligand dissociates, gate closes.
which body system relies heavily on ligand gates ion channels?
the nervous system; released neurotransmitters binds as ligands to ion channels
what are signal transduction pathways made up of?
protein kinases and phosphatases
what are protein kinases
enzymes that transfer a phosphate group from atp to another specific protein (activating the protein).
