cell communication Flashcards
name some examples of extracellular signalling molecules
proteins
nucleotides
amino acids
nuclei acids
dissolved gases
fatty acid derivatives
what are the four main signalling pathways
endocrine
paracrine
neuronal
contact dependent
paracrine signalling pathway
a form of cell-to-cell communication in multicellular organisms where cells release signalling molecules, called paracrine factors, into the extracellular fluid to influence neighbouring target cells or tissues
endocrine signalling pathway
a type of cell-to-cell communication in multicellular organisms that involves the release of signalling molecules called hormones into the bloodstream
neuronal signalling pathway
a specialized form of cell-to-cell communication that occurs within the nervous system.
contact dependent signalling pathway
a form of cell-to-cell communication that requires direct physical contact between the signalling cell and the target cell.
difference between the endocrine and the paracrine system
the paracrine system acts locally(in target cells that are in close vicinity), while the endocrine system can act in wide ranges throughout the body(so could be long or short range)
in what range can the neuronal system act
in long or short ranges
in what range can the contact- dependent system act
over long or short ranges
by how many types of signals is each receptor USUALLY activated by
1
how do cell surface proteins relay extracellular signals
via the intracellular signalling pathway
intracellular signalling pathway
this is when the signal from cell surface receptor is transmitted into target cell by intracellular signalling molecules
what are some of the things that intracellular signalling proteins can do to the incoming signals
they can;
relay it
amplify it
integrate it
distribute it
intracellular proteins can act as molecular switches, true or false
true
molecular switches
proteins or other molecules that can exist in two or more conformations or states and can transition between these states in response to specific signals or conditions
function of molecular switches
molecular switches play pivotal roles in determining the cellular response to external stimuli, allowing cells to adapt to changing conditions and maintain proper functionality. Examples include G proteins and protein kinases that switch between active and inactive states to transmit signals within the cell.
the two classes of molecular switches
allosteric
covalent
allosteric molecular switches
In allosteric molecular switches, a molecule binds to a specific site (allosteric site) on a protein, which induces a conformational change in the protein, affecting its activity. Allosteric regulators can be either positive or negative, meaning they can activate or inhibit the protein, respectively.
covalent molecular switches
Covalent molecular switches involve the addition or removal of specific chemical groups, such as phosphate groups (phosphorylation), to the protein, resulting in a change in its activity. These modifications can be reversible or irreversible.
example of allosteric molecular switches
Enzymes often exhibit allosteric regulation. An example is the allosteric activation of phosphofructokinase in glycolysis by fructose-2,6-bisphosphate. When fructose-2,6-bisphosphate binds to the allosteric site, it activates the enzyme, allowing glycolysis to proceed
example of covalent molecular switches
Protein kinases add phosphate groups to target proteins, often activating them. Protein phosphatases remove these phosphate groups, deactivating the proteins. Protein phosphorylation is a common covalent modification that acts as a molecular switch in many signalling pathways. For instance, the activation of the MAP kinase pathway involves a series of phosphorylation events.
what are the three main classes of cell surface receptors( extracellular receptors)
ion-channelled
G-protein-coupled-receptors
enzyme-linked receptors
what is the most common neurotransmitter
acetylcholine
ion-channelled receptors allow for the …………… transmission of signals across the synapses in the CNS
rapid
how do ion-channelled receptors allow for the flow of ions across the membrane
the membrane potential changes and an electric current is produced
which enzymes are the most frequent targets for G proteins
Adenylyl cyclase
Phospholipase C
what is the function of secondary messengers in G- protein coupled receptor signalling
they diffuse into the cell to act on intracellular signalling proteins
which enzymes make cAMP
adenylyl cyclase
what happens to the level of cAMP in the cell as due to extracellular signalling
cAMP levels increase
functions of cAMP
often activates the cAMP dependent protein kinases (PKA)
the activation of PKAs lead to increase in which effects in cellular signalling?
downstream effects
what are some examples of downstream effects initiated by the activation of PKAs
glycogen breakdown in the skeletal muscle
phosphorylation of target proteins
amplification of the signal
integration of signals
termination of signals
function of phospholipase C
makes inositol trisphosphate (IP3) and diacylglycerol (DAG)
what are the two signalling pathways activated by Phospholipase C
Inositol Trisphosphate (IP3) Pathway
Diacylglycerol (DAG) Pathway
largest group of enzyme-coupled receptors
receptor tyrosine kinases(RTKs)
describe dimerization in terms of RTKs
Binding of signalling molecule to extracellular domain of RTKs
what does the activation of tyrosine kinases on RTKs lead to
phosphorylation of each other on tyrosine residues
what does the phosphorylation of tyrosine residues result to?
a conformational change in the structure of tyrosine residues, which makes it easier for specific secondary signalling molecules to bind to
which enzyme does most RTKs activate
Ras(GTPase)
function of Ras (GTPase)
hydrolyse GTP to GDP
