Answer:
Thyrocalcitonin or TCT
Explanation:
Thyrocalcitonin or TCT is a non-iodinated calcium lowering hormone. It is originating from the parafollicular cells or C cells (C for calcium).
The thyroid gland consists of follicles of cuboidal epithelial cells. These cuboidal cells have a nucleus at the base. These are principal cells responsible for the synthesis of thyroid hormones.
In between these follicular cells, other high cuboidal cells are present, known as parafollicular cells / C cells. These cells synthesise the hormone TCT. When there is high levels of calcium ions in the serum, TCT will release. This lowers the high level of calcium ions in the blood and plasma to normal level. This is done due to the deposition of calcium in the bone.
Answer:
The two main reasons are nonpolar core of the bilayer and the active transport.
Explanation:
The membrane is structured to have two outer layers that are polar and an inner layer that is nonpolar.
If a membrane protein is exposed to the solvent, i<em>t will also have a polar side. It would be very difficult for the polar face of the membrane to move through the nonpolar core of the bilayer.</em> Therefore, this model is not feasible.
One major form of transport, active transport, moves solutes up the concentration gradient. <em>The binding of a solute and then release on another side of the membrane would only work for facilitated diffusion because it would cause a net movement of solutes down the concentration gradient.</em> It is unclear how energy could be expended to drive this process in the transverse carrier model.<em> Therefore, the transverse carrier model does not explain active transport.</em>
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