Feb. 18th

On Friday we completed a lab testing different food samples for the presence of lipids, starch and simple sugars. You can post your observation pictures and results chart(s) to your blog and then work on the following lab questions to post as well.

1. Describe a positive result for each of the tests that you performed in the lab.
      Lipids: butter tested positive as it left a greasy residue on the paper.
Carbohydrates: apple tested positive when the sample mixed with Benedicts solution was heated and turned an opaque orange.
Starch: bread mixed with a few drops of iodine showed it's true colours and turned a deep purple.

 
2. Starch molecules are large carbohydrate polymers. Find and post an image of the molecular structure of starch. What are the building blocks that starch molecules are made of?
      Starch molecules are made of two polysaccharides: amylose and amylopectin (which are made of glucose monomers).

STARCH! *

3. Thomas and Josh had interesting results to their simple sugar test - if you are following either of their blogs, look at their picture of their test tubes after they took them out of the hot water bath.
After 2 minutes, only 2 of the test tubes were yellow/orange, and the rest remained blue. They took the two positive test tubes out of the hot water bath and left the others in the hot water bath for 2 more minutes. At the end of the two extra minutes all the test tubes indicated a positive result. Based on your knowledge of carbohydrate molecules, why do you think they got these results?
     The single sugars such as glucose and fructose were able to break apart after two minutes, whereas it took longer to the polysaccharides to break their bonds in the Benedicts solution.

4. Making connections - Describe the passage of one of your food items through the digestive system, starting with the mouth & ending at the anus. Include the specific enzymes, accessory organ secretions & internal conditions the food/chyme would pass through from start to finish.
   Welcome carbohydrates, one and all, to the human digestive system. Our first stop will be the mouth, wherein you will be greeted by salivary amylase created just for you by the salivary glands, which will break you into simple sugars as you are ripped into small pieces by the teeth and tongue. Next, you will pass through the trachea and esophagus and into the stomach. Here you may rest in a pool of hydrochloric acid for a short while before continuing on into the small intestine. You will encounter pancreatic amylase to help you through the process of hydrolysis (though you may not visit the pancreas itself as it is an accessory organ), as well as maltase and sucrase which will further divide you into single sugars glucose and fructose. Later, in the large intestine, you will be absorbed with the help of villi, into the blood stream. Oh, and any left overs will be excreted out the rectum and anus. Well, enjoy your stay!

* Image found at this address:
http://www.patana.ac.th/secondary/science/ibtopics/ib%20human(05)/pages/5.1.htm