Protein Signals and Receptors Flashcards
what are the three different methods of short distance cell communication?
local signalling
direct contact between neighboring cells (gap junctions)
secreted messenger molecules e.g. synapses
what is an example of long-distance cell signalling?
hormones and the endocrine system
where is long-distance signalling found?
in plants and animals
what is autocrine signalling?
where the cell targets itself
what is juxtracine signalling?
when the cells are directly connected to each other
what is paracine signalling?
when cells target a nearby, non-connected cell
what is endocrine signalling?
when cells target a distant cell via the bloodstream
what are the 3 stages of signal transduction?
reception, transduction and response
what is reception in signal transduction?
when the signalling molecule (ligand) bonds to a receptor protein on the plasma membrane of the cell.
what is transduction in signal transduction?
when the message is communicated by a series of proteins (relay molecules) changing shape until a response
what is response in signal transduction?
when the response is carried out by an effector protein
what are examples of effector proteins?
metabolic enzymes
gene- regulatory proteins - long term, carefully controlled changes
cytoskeletal proteins - alters the cytoskeleton of proteins having long or short-term effects.
what is a long-term effect of a cytoskeletal protein?
stem cell change
what is the short-term effect of a cytoskeletal protein?
change in shape
which molecule is commonly used in signalling molecules?
GTP - guanosine tri-phosphate
what does protein phsophorylation do?
changes the structural conformation of the protein
what are key amino acids to phosphorylation events?
serine, threonine, tyrosine and histidene (phosphate groups are generally added to these amino acids)
what process is important in amplifying a signal?
phosphorylation
what is an example of a phosphorylation cascade?
adrenaline/epinephrine during the fight/flight response.
what are G-protein coupled receptors?
a diverse group of membrane receptors found only in eukaryotes
what are G-proteins made from?
7 alpha-helices
what do G-proteins have roles in?
light - cellular signals
molecules in food - taste
regulation of the immune system, blood pressure and heart rate
what do G-proteins do?
carry information from the receptor to enzymes which can activate an intracellular signalling pathway.
what are tyrosine kinase receptors? (RTKs)
receptor proteins that cross the membrane
what do RTKs do?
bind to extracellular ligands on the outside of the cell which can cause an internal signalling cascade
what are examples of ligands that bind to RTK?
EGF - epidermal groth factor
HGF- human growth factor
what are RTKs made of ?
2 monomers that are activated by binding to ligands and join together
what is needed for relay proteins to attach to activated RTKs?
all 6 tyrosine kinase bases inside the membrane to be phosphorylated
what is signal trasnduction?
when a signal changes from one form to another
can phosphorylation cascades activate transcription factors within the nucleus?
yes
what are P2X receptors?
ATP gated channels
what are ligand gated ion channels?
channels opened by ligand binding leading to an influx of ions in the cell which can cause signals and cellular responses.
what are steroid hormone receptors?
intracellular receptors
what are the characteristics of steroid hormone receptors?
normally hydrophobic, lipid soluble and can cross the membrane. e.g. oestrogen and testosterone
what is the typical end result of hormone receptor binding?
something entering the nucleus giving control over gene expression
where do steroid receptor proteins bind?
proteins inside the cell
what is ‘cross-talk’ ?
the different pathways and responses resulting from the same inital ligand
what are negative feedback loops?
the regulation of processes with the cell in response to external stimuli (homeostasis)
what are positive feedback loops?
a reinforcing or amplificaiton of signals
what is an example of a negative feedback loop?
lack operon
what is an example of a feedback loop gone wrong?
HPV binding to p53 and inactivating it, resulting in warts, mutations and cancer risks
what is an MAPK pathway?
when communication is started with RTK and the end goal is transcription
what is the fastest way to stop a signalling pathway?
using endocytosis to remove a receptor from the plasma membrane
