MICROANATOMY

Detailed explanation-1: -Water-soluble hormones cannot diffuse through the cell membrane. These hormones must bind to a surface cell-membrane receptor. The receptor then initiates a cell-signaling pathway within the cell involving G proteins, adenylyl cyclase, the secondary messenger cyclic AMP (cAMP), and protein kinases.

Detailed explanation-2: -Water-soluble hormone receptor activation: Water-soluble hormones, such as epinephrine, bind to a cell-surface localized receptor, initiating a signaling cascade using intracellular second messengers.

Detailed explanation-3: -Lipid insoluble hormones bind to receptors on the outer surface of the plasma membrane, via plasma membrane hormone receptors. Unlike steroid hormones, lipid insoluble hormones do not directly affect the target cell because they cannot enter the cell and act directly on DNA.