BIO 12 Lecture Notes - Lecture 27: Second Messenger System, Colloid, Phagocytosis
Document Summary
Thyroid follicles travel in the bloodstream and interact with receptor which stimulates t4. Hormone which is hydrophilic and uses camp as a secondary messenger. Step 1: tyrosine residues on thyroglobulin (tg) are inodiated at specific points at its structure. Step 2: addition of iodide will form dit, mit, which are grouped together, there will be a t3 or t4 precursor forming: t3 and t4 are not active. Step 3: thyroid hormones bound to tg are stored in the colloid. Step 5: uptake of iodinated tg molecules into the follicular cell via phagocytosis: engulfment of large particles by a cell. Step 6: phagosome containing tg molecule and thyroid hormone fuses with lysosome in the follicular cell: releases t3 and t4 into the cell. Step 7: lysosomal enzymes (proteases) break down tg, release t3 and t4, which diffuse into the bloodstream: t3 and t4 are hydrophobic, needs carrier proteins into the plasma to travel through it to find target cells.
