cell communication (signalling) Flashcards
four different types of extracellular signalling
endocrine (hormones)
paracrine
neuronal
contact-dependent
main difference is the speed and selectivity by which signals are delivered to their targets, and distance travelled
how does endocrine signalling work?
hormones produced in endocrine glands are secreted into the bloodstream and distributed around the body to target cells
describe paracrine signalling
paracrine signal molecules are rereleased by CELLS into extracellular fluid and ACT LOCALLY
describe neuronal signalling
transmitted electrically along a nerve cell axon, causing the release of neurotransmitters at nerve terminal
describe contact-dependent signalling
a cell-surface bound molecule binds to a receptor protein on an adjacent cell
how are signal molecules bound to target cells?
most extracellular signal molecules are large and hydrophilic hence cannot cross PM
binds to cell-surface receptor proteins, which generate intracellular signalling molecules in the target cell
once the signal molecule binds to the extracellular receptor, what happens?
receptor protein generates intracellular signalling proteins, which bind to effector proteins which alters cell behaviour
how do intracellular receptors work?
for small hydrophobic signal molecules that can pass the PM
transported by carrier protein, enters target cell and binds to intracellular receptor proteins
give a few examples of intracellular receptor binding molecules
cortisol
testosterone
vitamin D3
describe a simple gene regulatory circuit
this is how a cell’s gene expression is adjusted according to a signal from the cell’s environment
signal binds extracellular receptor –> gene-regulatory protein is activated
binds to regulatory DNA, produces another protein which binds to other regulatory regions to produce more proteins
effect of acetylcholine on heart pacemaker cells, salivary gland cells, and skeletal muscle cells
heart: decreased rate of firing
salivary: secretion
muscle: contraction
basically, same signal molecule can induce different responses in different target cells
name three main types of cell surface receptors
GPCRs
(not discussed further:)
enzyme-coupled receptors
ligand gated ion channels
/.?bvc
what are GPCRs?
G-protein coupled receptors
a very important class of cell surface receptor
activates/inhibits an enzyme/ion channel in PM, initiating intracellular signalling cascade
role of insulin
main anabolic hormone of the body:
regulates the metabolism of carbs/fats/protein by promoting absorption of carbs (esp glucose)
how do beta cells regulate insulin?
beta cells are sensitive to blood sugar levels
high blood glucose –> secrete insulin
low –> inhibit secretion
