Students should say the cracker went from being salty to sweet. The reason is that the cracker is composed of starches (polysaccharides). However, your spit contains amylase (a digestive enzyme) that breaks the polysaccharide down into monosaccharides (sugar).
Structure of starches. Something in your spit goes in there and breaks the bonds in between each of the sugar (glucose) units.
How would we test if this is what actually happened? Before putting in your mouth, cracker would test positive for Iodine test (indicating presence of starch). After, however, it would test negative for the iodine and positive for the Benedict’s test.
Emphasize importance of 3D structure and how the folds are what hold the active site together.
Alcohol dehydrogenase converts alcohol into a less harmful substance once it is in your system to rid your body of its poisonous effects. If you would like to expand upon this, you could ask them who is lacking in this enzyme (on average, women and Asians—Asian glow!).
Enzymes can carry out synthesis/addition reactions where 2 substrates are combined.
Enzymes can also carry out degradation reactions where a substrate composed of many monomers (a macromolecule or polymer) is broken down into individual parts.
DO NOW! (be ready to discuss)
You will find a cracker on your desk.
Put the cracker on your tongue for 5 minutes (NO CHEWING).
Chemical Tests? Benedict’s reagent is used to test for simple sugar like glucose and fructose (mono-saccharides). When heated , Benedict’s reagent changes color from light blue to red/orange if a simple sugar is present. + -- + Iodine solution is used to test for the presence of polysaccharides (starch). If starch is present, a color change from amber to purple/black occurs. Starch No starch