Citat:
Ursprungligen postat av
manne1973
Ska lära dig ett tips nu. ANVÄNDE ENGELSKA WIKIPEDIA:
https://en.wikipedia.org/wiki/Iodine_test
"The iodine test is used to test for the presence of starch. When treated with IKI solution—iodine dissolved in an aqueous solution of potassium iodide—
the triiodide anion (I3−) complexes with starch, producing an intense blue/purple colour. The colour can be detected visually with concentrations of iodine as low as 2×10-5 M at 20 °C. However, the intensity of the color decreases with increasing temperature and with the presence of water-miscible organic solvents such as ethanol. The test cannot be performed at very low pH due to the hydrolysis of the starch under these conditions.[1]"
Eftersom du tog upp biologi så kan jag bifoga:
"Iodine's main role in animal biology is as a constituent of the
thyroid hormones thyroxine (T4) and triiodothyronine (T3). These are made from
addition condensation products of the amino acid tyrosine, and are stored prior to release in an iodine-containing protein called thyroglobulin. T4 and T3 contain four and three atoms of iodine per molecule, respectively. The thyroid gland actively absorbs iodide from the blood to make and release these hormones into the blood, actions that are regulated by a second hormone TSH from the pituitary. Thyroid hormones are phylogenetically very old molecules that are synthesized by most multicellular organisms, and that even have some effect on unicellular organisms.
Thyroid hormones play a basic role in biology, acting on gene transcription to regulate the basal metabolic rate.[citation needed] Total deficiency of thyroid hormones can reduce basal metabolic rate up to 50%. Excessive production of thyroid hormones can increase the basal metabolic rate by 100%.[citation needed] T4 acts largely as a precursor to T3, which is (with minor exceptions) the biologically active hormone. In amphibian metamorphosis iodine and thyroid hormones exert a well-studied experimental model of apoptosis on the cells of gills, tail, and fins of tadpoles.[52]"