AP Syllabus focus:
‘Cells communicate via direct cell contact or chemical signaling that allows them to coordinate activities over varying distances.’
Cells survive as coordinated systems, not isolated units. Communication lets cells detect changes, share information, and synchronise behaviours like growth, movement, secretion, and gene activity across tissues and entire organisms.
Core idea: what “cell communication” means
Cell communication (cell signalling): The transmission of information between cells that produces a specific response in a target cell.
Communication requires a signal source, a target that can detect the signal, and an appropriate response; the major difference among modes is how the signal travels.
Practice Questions
FAQ
Hydrophobic hormones often bind carrier proteins in plasma, which improves solubility, reduces loss in urine, and extends half-life.
Different cells can express different receptor subtypes or coupling proteins, so the same ligand–receptor binding can trigger distinct downstream responses.
The electrical impulse travels far, but the chemical step (neurotransmitter diffusion) occurs only across the tiny synaptic cleft, keeping targeting precise.
They use rapid ligand degradation, uptake by neighbouring cells, binding to extracellular matrix, and restricted release sites to confine diffusion.
It is chemical signalling in microbes where secreted molecules accumulate with population density, triggering coordinated gene expression once a threshold concentration is reached.
