Signalling Flashcards
signalling: basic principles- transmembrane proteins, signal transduction
- binding of ligand to receptor protein in cell plasma membrane -> changes intracellular portion of receptor
- receptor: transmembrane proteins (parts both out of cell/ in cytoplasm)
- signal from ligand binding causes phosphorylation of proteins (change shape/ function)
- signal transduction (cascade of phosphorylation) causes one or more responses in cell, (including change in protein function/ gene transcription)
ligand interaction: not lipid soluble
bind to receptors on surface of target cell
ligand interaction: most not lipid soluble
bind to receptors on surface of target cell
ligand interaction: lipid soluble
often bind to receptors inside target cell
eg. adrenaline signalling
- fight/flight response
acute stress response:
- nausea, loss of appetite
- increase energy and agitation
- stimulated by epinephrine (adrenaline) from adrenal gland
cAMP:
- cyclic adenosine monophosphate
- secondary messenger in cell
- activates kinase proteins which add phosphate group to enzyme -> breaks down glycogen into glucose for energy
release glucose from liver cell: pathway
adrenalin detected by adrenergic receptor - G protein dissociates - cAMP activates - kinase - breaks down glycogen - glucose - energy
list phases of cell signalling:
- reception
- transduction
- response
reception:
ligand binds to receptor
transduction:
receptor activates signal transduction molecule
- sometimes initiates signalling cascade
response:
- eg. stimulates glycogen breakdown
list types of receptors which bound to ligands:
- receptor tyrosine kinase
- G-protein coupled receptor
- ligand-gated ion channel
receptor tyrosin kinase:
- paired receptor
- cytoplasmic portions cross phosphorylate at tyrosine residues
G-protein coupled receptor:
- receptor coupled with G protein
- when activated activates adenylyl cyclase
ligand-gated ion channels:
- open to allow ion flow across membrane
- direct response
ion:
- charged atom/ molecule
- neither negative/positive charge can pass membrane
mitochondria:
- produce ATP
- C6H12O6 + 6O2 –> 6CO2 + 6H2O
- 30-32 ATP per molecule glucose
- opposite of photosynthesis
major reaction pathways of ATP production:
- glycolysis
- Krebs cycle (citric acid)
- electron transport phosphorylation (chemiosmosis)
aerobic respiration:
- production of ATP dependent on oxygen
anaerobic fermentation:
- oxygen limited
- glycotic products metabolised this way
- independent of mitochondria
phosphorylated:
- when signalling receptors activated, cytoplasmic proteins are phosphorylated
- phosphate group added to molecule
- usually donated from ATP
- protein kinase transfer phosphate
significance: phosphorylation
- frequently changes proteins confirmation and surface charge
de-phosphorylation:
protein phosphotases removes phosphate from protein
significance: phosphorylation/ de-phosphorylation
- act as molecular switch, turning protein on and off
transduction:
- cascade of molecular interactions relay signals from receptors to target molecules in cell
significance: signal transduction
- multiple steps
- can amplify signal
- more opportunity for coordination and regulation of cellular response
response to a signal:
- regulation of one or more cellular activities
cytoplasmic: and eg
output response in cytoplasm
- eg. change in enzyme’s activity
nuclear: and eg.
output response in nucleus, effecting change in gene expression
- final activated molecule may function as transcription factor (binds to DNA, blocks/ enhances transcription of gene)
list two ways cells direct changes in proteins via signal pathway:
- phosphorylation
- gene regulation
faster response:
- phosphorylation quickly alters protein activity (activate/deactivate) but only affect existing proteins in cytoplasm
slower response:
- gene regulation can lead to production of new proteins/ change protein conc. in cell
- if gene expression is down-regulated, takes some time for cell concentration of gene product (protein) to deplete
insuline binding results:
- several responses
- most anabolic
- stimulates synthesis and storage of carbohydrates, proteins, fatty acids
