Name: ______Date: ______Period:______AP

Investigation: Protein Digestion

Student Objectives:

  1. Students will be able to describe the difference between mechanical and chemical digestion
  2. Students will be able to describe the function and parts of the digestive system.

Introduction______

What is a protein?

A protein is a large organic compound constructed of smaller organic compounds called amino acids. Proteins are used by plants and animals to perform many different functions. Collagen is an example of a protein, which keeps are skin tight and flexible. As we age, sun damages this protein and results in wrinkling of our skin. Other examples of a protein include Antibodies, which are a part of our immune system and defend our bodies from infections.

Why must we eat protein?

Our body must generate millions of proteins each day to maintain our bodily functions. In fact, about 40% of our body is protein. To construct these proteins, we must digest or break down other proteins to collect the parts needed to build new proteins. More simply, our body recycles proteins, using the left-over parts to construct new proteins. Not eating enough protein can result in stunted growth, loss of muscle mass, and a severely weakened immune system.

How do our bodies break down or digest protein?

What is the first thing you do when you place food in your mouth? You chew. Your mouth is where digestion or the breakdown of food begins. Your teeth tear and shred the food into smaller pieces that can more easily go down your esophagus, the tube that carries food from your mouth to your stomach. This form of digestion is known as mechanical digestion, because it changes the food physically and not chemically. Chemical digestion also begins in the mouth but occurs mostly in the stomach and the small and largeintestines. Inside the stomach and intestines are small biological machines called enzymes that chemically break down food into small nutrients. Acid in the stomach also helps break down food. The nutrients are carried by the blood and shared with the entire body. Anything that is not absorbed by the blood becomes waste as removed from the body.

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Pre-investigation Questions______

  1. Where in the body does mechanical digestion occur?
  1. Stomach
  2. Mouth
  3. Small Intestine
  4. Large Intestine
  1. Where in the body does chemical digestion occur?
  2. Stomach
  3. Large and Small Intestine
  4. Mouth
  5. A and B are both Correct
  1. Burning is to paper as ______is to food.
  2. Chemical digestion
  3. Mechanical digestion
  1. Tearing is to paper as ______is to food.
  2. Chemical digestion
  3. Mechanical digestion
  1. Which answer below correctly orders the movement of food through the digestive system
  2. Mouth, esophagus, stomach, small intestine, large intestine
  3. Mouth, esophagus, small intestine, large intestine, stomach
  4. Esophagus, mouth, stomach, small intestine, large intestine
  1. Using your own words, describe the function of the digestion system.

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Instructions______

  1. Label your three test-tubes as shown below
  2. Period# - Group# - A,B, or C (Example: 2-3-A)
  1. Add the following material to test-tubes:
  2. Tube A: 10 drops of Water
  3. Tube B: 10 Drops of 1% HCl (Hydrochloric Acid)
  4. Tube C: 10 Drops of 1% HCl + small scoop of the enzyme pepsin

Think to yourself, why are we adding these different substances?

  1. Using your hands, mash the small piece of meat in the plastic bag.

Think to yourself, what type of digestion is this similar to?

  1. Divide the meat into 3 equal parts and place 1 piece into each test-tube.
  1. Draw and label your observations in the box below.

Test-Tube A / Test-Tube B / Test-Tube C
Day
1
(Today) / / /
Day
2
(Tomorrow) / / /

Conclusion Questions______

  1. How do your observations for test-tubes A, B, and C, differ from day 1 and day 2?

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  1. Which combination of substances were best for breaking down or digesting the meat? Support your answer with your observations.

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  1. Describe when in your experiment did you perform mechanical and chemicaldigestion?

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  1. Provide two reasons why the test-tube is a good model of our stomach and 2 reasons why it’s a poor model?

Advantages:

  1. ______
  2. ______

Disadvantages:

  1. ______
  2. ______