1. Describe a positive result for each of the tests that you performed in the lab.
- Food items that were positive for lipids were butter and the cupcake. After rubbing the food item on the piece of paper and letting it dry, the paper turned greasy and almost transparent.
Food items positive for starch were the cupcake, bread, and pancake. These food items turned black after iodine was dropped onto them.
Food items positive for simple sugars were cheese, butter, orange, apple, lettuce, and pancake. They turned into milky oranges and yellows.
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 up of?
- Starch molecules are made up of glucose.
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?
- I think they got those results because carbohydrate molecules are very large and take long to break apart. As the two blue test tubes continued to sit in the hot water bath, the carbohydrate molecules were given more time to separate.
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.
- a) First, food is put into the mouth. You chew and break up the food into smaller pieces with your teeth, to make more surface area. Salivary amylase is created in the salivary glands and released into the mouth. Salivary amylase breaks down starch into maltose. The tongue then sends the bolus down the esophagus. Peristalsis in the esophagus helps push the bolus down into the stomach. Peristalsis is involuntary contractions in the esophagus. The esophagus has a pH level of 7.
b) The bolus then passes the cardiac sphincter and drops into the stomach. The stomach contains gastric juice, which contains HCl, mucus, and the enzyme pepsin. The mucus is a layer over the stomach lining that prevents the acidic HCl from burning a hole into it, which would be an ulcer. Pepsin in the stomach breaks down proteins. The stomach has a pH level of 2.
c) The pancreas, liver, and gall bladder are accessory organs. The pancreas creates pancreatic juice with contains pancreatic amylase, trypsin, lipase, nuclease, and sodium bicarbonate. Pancreatic amylase breaks down starch. Trypsin breaks protein into peptides. Lipase breaks down lipids into glycerol and fatty acids. Nuclease breaks down DNA and RNA into nucleotides. The liver creates bile, and it is then stored in the gall bladder.
d) Single tablespoons of bolus (now chyme) enters the small intestine via the pyloric sphincter. The first 25 cm of the small intestine is called the duodenum, which creates small intestine juice. It has 3 components: nucleosidase wich breaks down nucleotides into sugar + phosphate + base, maltase which breaks maltose into glucose, and peptidase which breaks peptides into amino acids. Bile is also released into the duodenum. Bile emulsifies fat and lipid molecules, making them into small fat droplets. The rest of the small intestine absorbs nutrients like glucose, amino acids, and fatty acids. The small intestine has a pH level of 7.
e) Chyme continues through small intestine, and then reached large intestine. Connected to the start of the large intestine is the appendix. The appendix really has no function. The large intestine absorbs H2O and contains bacteria E. Coli. The large intestine has a pH level of 7.
f) Once through the large intestine, the chyme turns into feces. Feces collects an stores in the rectum, and voluntarily released through the anus.
