Life of Pie (Digestive System Project)

This is the incredible story of how the digestive system works. It's an amazing feat that the human body can do. We will discover how food gets broken down into small microscopic pieces and is then absorbed by the body. Without the digestive system, all of the food we eat wouldn't have a place to get stored, have no way of leaving our body, and will have no way to give us the nourishment we need to get through the day. Now, let's dive into the deep and wonderful world that is the digestive system.

For this example, we will be looking into how our digestive system takes in and absorbs a piece of pie. When a person takes their bite out of the pie, their teeth grind and chew the food into smaller, more manageable pieces. The tongue on the other hand moves the pieces of food around the mouth and towards the areas of the teeth that will best break down the food. This is called physical digestion. Chemical digestion happens when salivary glands secrete salivary amylase, and enzyme that breaks down the starch in the pie into smaller polymers called maltose. Polymers are molecules that are too big to be absorbed in our body and need to be broken down into their smallest components called monomers. Salivary amylase is one of the many enzymes that break down complex food. After the food has been physically and chemically digested, the food (now called a bolus) goes through the pharynx and down the esophagus. A small flap called the epiglottis stops the bolus from going to the respiratory system.

The bolus goes down the esophagus via peristalsis. These are involuntary muscle contractions that move the food along our digestive tract. The food finishes its way down the esophagus and enters the stomach through the cardiac sphincter, a muscular valve that opens and closes. After going through the cardiac sphincter, it goes to everyone's favorite and well known organ, the stomach. The stomach is the place where we store all of our food. The bolus sits inside the stomach's gastric juice, which is made up of three components: HCl, mucus, and an enzyme called pepsin. Mucus protects the stomach from getting burned by the acidic HCl, and pepsin breaks down any protein molecules that might have been in the pie into polymers called polypeptides. The bolus stays in the bolus and gets turned into a more liquid mixture called chyme. Finally, the chyme travels to the pyloric sphincter, another muscular valve that separates from the stomach from the small intestine.

Now the chyme travels to the small intestine, the place where the food's nutrients are absorbed. The first 25 cm of the small intestine is called the duodenum. Here, pancreatic juice is released and food starts breaking down into even smaller pieces. Lipase breaks down lipids into glycerol and fatty acids, and nuclease breaks down RNA and DNA into nucleotides. Trypsin breaks polypeptides into peptides, and pancreatic amylase breaks down starch into maltose. Although food doesn't pass through the pancreas, it is an essential organ to our digestive system, as with two other organs, the liver and the gall bladder. The liver produces bile and is stored in the gall bladder, which then squirts the bile in the duodenum along with pancreatic juice. Bile emulsifies large fat globs into small droplets. The food travels deeper into the small intestine where the polymers finally break down into their building blocks. Maltose turns into glucose, a sugar that can be absorbed. Peptides break into amino acids that can also be absorbed. Now that everything has been broken down, the small intestine can now absorb the nutrients. Small bumps called villi are contained in the small intestine where they have even smaller bumps on them called microvilli. These bumps increase surface area so more nutrients can be absorbed. Monomers glucose and amino acids go straight to the bloodstream while glycerol and fatty acids go up into the lacteal. When all of the nutrients are absorbed, the waste product goes into the large intestine, and so ends the life of the once beautiful and delicious pie.

The waste ( now called feces) is moved through the large intestine where the water is being absorbed from the feces. The HCl from the gastric juice doesn't affect the large intestine because of sodium bicarbonate that was part of the pancreatic juice. When food is ready to be disposed of, the feces is stored into the rectum, where it goes through the anal sphincter and out the anus. Thus ends the mystifying adventure of how food is broken down, absorbed, and gotten rid off. The once complex and big pie was turned into small microscopic pieces of molecules that gave us fuel and nutrients extremely important to our body. This wouldn't have been accomplished without the help of the digestive system.

Starches, Lipids, and Sugars Lab

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.
QUESTIONS
1.  Describe a positive result for each of the tests that you performed in the lab.

For a positive test on lipids, we looked for smuding on the paper. If the smudge was see through, then the result was positive for lipids. To find a positive result for starch, the food had to turn black after putting a few drops on iodide on the food. For the simple sugar, the food tested postitive if the test tube changed from a clear, blue liquid, to a yellow/orange opaque liquid. 

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 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? 

Due to the heat of the hot water, the food slowly got broken down. Since carbohydrates are made up of glucose, eventually the were broken and became positive for glucose.

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.

After taking a bit out of an bread, your teeth start breaking down the chunk into tiny pieces while the tongue moves the food into the appropriate teeth. Salivary glands also start to produce salivary amylase, and chemically break down the bread. The salivary amylase breaks down the starch in the bread, to maltose. The food, or bolus, which is it now called, goes down the esophagus via peristaltic contractions. From the esophagus, the bolus goes through the cardiac sphincter and enters the stomach. the food is stored there, and the hydrochloric acid turns the bolus into chyme. After that, peristalsis moves it from the stomach, through the pyloric sphincter and enters the duodenum. In the duodenum, the maltose breaks down into the monomer glucose. The small intestine is structured in finger like projections called villi, which maximize the surface area for absorbing the nutrients from the food. The food then goes through the large intestine, where it is stored and water is absorbed. The food (now called feces) is stored in the large intestine until it is ready to be passed through through the rectum, and out the anus, using the anal sphincter. 

RESULTS
        Positive for:     Starch.                           Lipids.                      Simple Sugars

1. Bread.            Yes.                               No.                                 Yes
2. Tomato.          No.                                No.                            Not used
3. Lettuce.          No.                               No.                                   No
4. Orange.         No.                                No.                              Not used
5. Pancake.        Yes.                              No.                                  Yes 
6. Cheese.         No.                                 No.                                  No 
7. Butter.            No.                               Yes.                             Not used
8. Apple            No.                                No.                                 Yes
9. Cupcake.       Yes.                               Yes.                               No

OBSERVATIONS

Simple Sugars Result

FAKE!

After watching the video that Ms.Phillips posted on her Biology blogspot, Thomas and myself have come to the conclusion that the video was fake. First of all, because it is a liquid, gravity would not allow the water to create that shape because liquids flow and gravity would push it down. And although water has hydrogen bonds to allow it to be cohesive, they are not strong enough to allow it to form a solid shape instead of flowing like liquids do. That is why we believe that video is fake.