Thursday, March 20, 2008,
Semi-Pro is the best movie ever!! Shame to those who never watch it.
But anyway,BIO HOMEWORK REMINDER!!DUE NEXT MONDAY (24 March):1. SPA Skill A2. Enzyme summary graphs
Ignore the microscopy tutorial since we don't have one. Yet. (I confirmed with Widjaja already). Ignore OK?
And regarding the SPA A pg 13 where they ask you to identify the "presence of some of the intermediate products" (of the digestion of starch to maltose by enzyme maltase), a quick search on wikipedia gave me this:Dextrin"Dextrins are a group of low-molecular-weight carbohydrates produced by the hydrolysis of starch. Dextrins are mixtures of linear α-(1,4)-linked D-glucose polymers starting with an α-(1,6) bond. Because branched amylopectin and glycogen also contain α-(1,6) bonds, which α-amylase cannot hydrolyze in humans, the digest resulting from this action contains a mixture of dextrins. They have the same general formula as carbohydrates but are of shorter chain length. Industrial production is, in general, performed by acidic hydrolysis of potato starch. Dextrins are water-soluble, white to slightly yellow solids that are optically active. Under analysis, dextrins can be detected with iodine solution, giving a red coloration.
" - WikipediaSource
And from encyclopedia.com:
"Dextrin any one of a number of carbohydrates having the same general formula as starch but a smaller and less complex molecule
. They are polysaccharides and are produced as intermediate products in the hydrolysis of starch by heat, by acids, and by enzymes
. Their nature and their chemical behavior depend to a great extent on the kind of starch from which they are derived. For example, some react with iodine to give a reddish-brown color, others a blue, and still others yield no color at all." - Encyclopedia.comSource
So basically it means that the α-(1,6) bonds at branch point in amylopectin cannot be hydrolysed by amylase (α(1,6) glucosidase is needed in addition for complete digestion), resulting in the formation of polysaccharide dextrin, which gives a red/reddish-brown coloration in iodine solution.
DON'T WRITE THIS IN YOUR ANSWER THOUGH unless you trust me a lot.
From BIO REP,