1. Describe a positive result for each of the tests that you performed in the lab.
A positive test for carbohydrates is when the substance in the test tubes turned a cloudy orange colour. A positive test for fats is when the residue left on the paper was clear, oily and transparent. A positive test for proteins when the food item turned a dark purple/black colour.
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?
The building blocks are made 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 after excessive heating to the substance, it breaks down further into glucose molecules. Therefore, the glucose plays a role in turning the substance positive.
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.
Food first enters through the mouth (oral cavity). Once in the mouth, salivary glands secrete salivary amylase that break down the food by chemical digestion. The teeth also break down the food into smaller more manageable pieces by physical digestion. The tongue pushes the bolus of food to the back of the throat, to be swallowed. By peristalsis the food is pushed passed the pharynx. The epiglottis makes sure that the food travels to the stomach and not into the lungs. The cardiac sphincter allows the food to enter the stomach. Pepsin, HCl and mucus make up the gastric juices. They are a part of chemical digestion. The food inside is now called chyme. One teaspoon at a time food passes the the pyloric sphincter and enters the first 25 cm of the small intestine, the duodenum. Liver produces bile and stores it in the gall bladder. The liver also processes fats, proteins and carbohydrates. It even filters the blood. From the gall bladder, through a small tube, is the pancreas that produces trypsin, sodium bicarbonate, pancreatic amylase and lipase. Maltase, trypsin, pancreatic amylase, lipase and nuclease is excreted in the small intestine which helps with further break down of food. Villi and microvilli increase the surface area which helps in the absorbing of nutrients. After the small intestine there is the large intestine (starting with cecum) which compacts the left over material, absorbs water and contains e.coli. If the material gets stuck in the cecum it can go into the appendix and cause appendicitis. The rectum collects the feces and stores the waste. Finally, feces pass through the anus and anal sphincter.
