Cell signalling CAQ

📍 Cell signalling Created Tags how does Cell surface membrane facilitate cell signalling Describe the structure and properties of CSM CSM consists of hydrophobic fatty acid tails which forms hydrophobic interactions and consists of hydrophilic phosphate heads Allow embedment of glucagon and insulin receptors so that insulin and glucagon are able to interact with their receptor by binding to the extra cellular ligand binding site since insulin and glucagon are large and hydrophilic, unable to pass through the hydrophobic core of the phospholipid bilayer CSM is fluid and allows tyrosine receptor kinase to dimerise after binding of insulin to the ligand binding site, hence cross-phosphorylation of tyrosine amino acid residues at the intracellular tails by tyrosine kinases of other receptor monomer Also enables activated G protein bound to GTP to move to bind and activate adenyl cyclase so that ATP can be converted to cAMP to trigger a phosphorylation cascade in order to eventually reach effector molecules in order to elicit a cellular response Advantages of cell signalling pathway/ why are ligands never found within the cells/ why are receptors found on cell surface membrane and never within cells/ why should receptors span the cell membrane The cell surface receptor allows signal from ligand to be relayed from outside the cell into the cell, this advantageous as ligand is hydrophilic and large, has a August 7 , 2025 1240 PM Cell signalling 1

polar region which makes it unable to pass through the small gaps in the phospholipid bilayer of the membrane hydrophobic core of the phospholipid bilayer as it will be repelled Hence receptor outside to allow binding of ligand at the extracellular binding site Signal can be transduced to cytoplasmic side of cell through change in intracellular domain The receptor of the cell signalling pathway is specific to the ligand and this specific ligand receptor interaction will elicit specific cellular responses Small number of signal molecules binding to the receptors can produce a large cellular response inside the cell as the number of activated molecules increases with each catalytic step in the pathway facilitating signal amplification One signal molecule can trigger many signal transduction pathways in a cell and elicit many different cellular responses by activating intracellular domain of receptor signal molecule can activate genes in nucleus upon binding to cell surface receptor without the need to move into nucleus How each protein kinase in the cascade is activated?/ how does a signalling cascade amplifies signal?/how release of cAMP leads to a cellular response? cAMP binds and activates protein kinase A Activation of PKA will initiate a sequential activation of kinases resulting in a phosphorylation cascade The active protein kinase in the previous step transfers a phosphate group from ATP to the inactive protein kinase, phosphorylating it and hence activating it, act