In what tissue must vitamin D be chemically altered to yield a compound that is fully active?
Liver and kidney
In what tissues must a molecule of vitamin D be chemically altered to yield a compound that is fully active?
Vitamin D is the sunshine vitamin because sunlight helps synthesize it. Sunlight converts a compound in the skin called cholecalciferol to a vitamin D precursor called vitamin D3. This compound then enters the bloodstream and travels to the liver and kidney for processing. After leaving the kidney, vitamin D is active and ready to use.
The name is derived from a- (meaning "no" or "anti") and scorbutus (scurvy), the disease caused by a deficiency of vitamin C. L-Ascorbic acid - the active vitamer of vitamine C - was historically the first chemical compound to be synthesized (by by Haworth and Szent-Györgyi) and identified as vitamin C.
Corrosion is a chemical reaction between metal and some corrosive agent found in the atmosphere, usually oxygen or sulfur dioxide. Iron is a chemically active element, which is usually found as an ore (not counting meteorites); we refine it for our purposes, but in doing so we are creating a chemically unstable substance, in an environment that has a chemically active atmosphere.