*cont'd. the conversation about why does the blue color of Iodine disapear when amylose reacts with saliva. The answer I chose(wrote in earlier post) was incorrect.
the choices remaining are 1. Saliva causes the amylose chain to uncoil soIodine is no longer trapped.
2. Saliva reacts with Iodine causing it to be unable to complex with the amylose coil.
3. Saliva cause the amylose chain to break into short chains and then into glucose which does not coil and so does not trap Iodine.
I have been tring to read everything I can about this subject, but nothing is saying anything that concerns the choices left. Any help would be welcomed as I have a final next week in class.
4 answers
The explanation I gave you yesterday (plus the site I posted) is correct. Of the choices listed in your post today, #3 is the correct one. Compare this with my earlier answer---Saliva contains amylase, an enzyme which breaks amylose down (and it breaks it down into smaller molecules and eventually to glucose) and the blue color formed with the combination of starch and iodine turns colorless when there is no starch. (Amylose is a starch.)
thank you for explaining it more to me. I was not seeing anything about breaking it down eventually to glucose and trapping or not trapping the iodine.
I don't know why but I keep thinking that my original answer could be correct as well. that because of the Amylose in saliva,it replaces the I2 in the amylose coil and thus removes the color.
I don't know why but I keep thinking that my original answer could be correct as well. that because of the Amylose in saliva,it replaces the I2 in the amylose coil and thus removes the color.
No, your original answer is not correct. There is no replacing the I2 in the amylose coil; in fact the I2 is STILL THERE. The original blue color is due to a complex between starch (amylose) and I2. (I'm an analytical chemist and we use starch in titrations with I2. When the blue color disappears we know all of the I2 has been titrated.) This question is a little different from that. When the starch/I2 complex is added to saliva, the enzyme in saliva (amylase) begins the digestion process by breaking the starch down into smaller pieces and eventually to glucose.(It does this will all of the carbohydrates.) When the starch is gone, there is no starch to form the starch/I2 blue color so the blue color disappears. I2, by itself, is not blue. (For whatever it's worth, not all starches form the blue color with I2. For quantitative purposes, amylose is the best one to use and laboratory houses sell the stuff which is purified from potato starch.)
I understand it more now, thanks DrBob222 for taking the time to help me.
1 answer