BIOL 2160 Lecture Notes - Lecture 5: Secretion, Membrane Transport Protein, Codocyte
Document Summary
Chapter 5: chemical signlaing: direct: two cells that are physically connecting, joined by protein channel called connexon. Ions, small signaling molecules, transfer easy between two cells . Disadvantage: bad for long distance. (need to be touching: cells in heart connected by gap junctions (coordinated activation activate one cell and have it spread throughout heart, indirect: involves chemical messenger (ligand) and receptor. Ex: pancreas: advantage: speed, neurotransmitter: signaling molecule is neurotransmitter, target cell is another neuron/muscle cell/gland. Neuro signaling needs secretory cell to be neuron: advantage: speed, endocrine (hormones): involves molecule entering blood stream. No blood inside cells or around cells (closed circulatory system), blood stays in blood vessels. If it likes water doesn"t like membrane (nonpolar: hydrophilic ligand can"t just cross membrane, receptor has to be on outside of cell. If it has to compete w more than one ligand: opposites attract: receptor activation, concentration of ligand, expression level of receptor (# of receptors, affinity of receptor for ligand.
