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Chapter 23: Problem 44

Amylase, the enzyme present in the mouth, catalyzes the digestion of starch. The pH of the mouth is almost neutral. a. Do you think that amylase is active in the stomach after you swallow the food? Why or why not? b. Design an experiment you could perform to test your answer to item a. Note: A common test for the presence of starch is the addition of tincture of iodine, which will produce a blue color if starch is present.

Short Answer

Expert verified
Amylase is inactive in the stomach due to its acidic pH. To test this, incubate starch-amylase mixtures at different pH levels and check for starch presence with iodine.

Step by step solution

01

Understanding the pH of the stomach

The stomach is highly acidic with a pH around 1.5 to 3.5, which contrasts with the almost neutral pH of the mouth.
02

Effect of pH on amylase activity

Amylase is most active around a neutral pH. The acidic environment of the stomach can denature amylase, reducing or inhibiting its activity altogether.
03

Conclusion for part a

Amylase is likely inactive in the stomach due to the highly acidic pH that denatures the enzyme.
04

Designing an Experiment to Test Amylase Activity

To test amylase activity at different pH levels, prepare three test tubes: one with neutral pH (control), one with acidic pH (to simulate stomach conditions), and one with the pH adjusted to show the difference more clearly.
05

Preparing the samples

Add starch solution to each test tube along with a small amount of amylase enzyme, then place them in water baths set to body temperature (37°C) for a set time.
06

Testing for starch presence

After the incubation period, add tincture of iodine to each test tube. Observe the color changes: a blue color indicates the presence of starch, while no color change signifies starch digestion by amylase.
07

Analyzing the results

Compare the results from the neutral and acidic test tubes. Expect a blue color in the acidic pH tube, indicating starch presence, and no blue color in the neutral pH tube, indicating starch digestion.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Amylase
Amylase is an enzyme found in saliva that helps break down starches into sugars. It's crucial for beginning the digestive process as soon as you start chewing food.
Enzymes like amylase speed up chemical reactions in your body. Amylase specifically targets starch, a complex carbohydrate, breaking it down into simpler sugars like maltose.
Without this enzyme, your body would struggle to convert starches into energy efficiently.
It's fascinating to note that amylase works optimally at a neutral pH, which is why its activity starts in the mouth rather than in other parts of the digestive system.
pH Levels
The term 'pH' refers to the acidity or alkalinity of a solution, measured on a scale from 0 to 14. A pH of 7 is considered neutral, below 7 is acidic, and above 7 is alkaline or basic.
The mouth has a pH close to neutral, around 6.5 to 7, which allows amylase to function effectively. However, the stomach is highly acidic, with a pH of about 1.5 to 3.5. This acidic environment is essential for digesting proteins and killing harmful bacteria that enter with food.
Due to this acidity, enzymes like amylase become denatured and inactive. Denaturation refers to the process where the enzyme's structure is altered, making it unsuitable for catalyzing reactions.
Starch Digestion
Starch digestion begins in the mouth, thanks to amylase. When you chew food, amylase starts to break down starch into simpler sugars.
This preliminary digestion is critical because it makes the nutrients more accessible when the food reaches the intestines. Starch is a complex carbohydrate, consisting of long chains of glucose molecules. The breakdown of these chains by amylase is an essential step in converting the starch into glucose that your body can use as energy.
However, when food reaches the stomach, the acidic environment halts this process as amylase becomes inactive. The stomach's main job is to digest proteins with the help of pepsin, rather than carbs.
Experimental Design
To test whether amylase is active in the stomach, you can design a simple experiment. You'll need three test tubes to represent different pH conditions.
  • Test Tube 1: Neutral pH (around 7)
  • Test Tube 2: Acidic pH (similar to stomach, 1.5 to 3.5)
  • Test Tube 3: Adjusted pH, somewhere between neutral and acidic to make observations clearer
Add equal starch solution to each test tube and a small amount of amylase enzyme.
Place these test tubes in water baths set to body temperature (37°C) and let them sit for a specific duration. After this period, add tincture of iodine to each tube. Iodine turns blue in the presence of starch, indicating that it hasn't been broken down.
Compare the results:
  • If the iodide turns blue in the acidic solution, it means amylase is inactive.
  • If there's no color change in the neutral test tube, it indicates starch digestion.
This simple experiment can help illustrate how pH affects enzyme activity, reinforcing the critical role of pH in biological processes.

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Most popular questions from this chapter

Carbohydrates, fats, and proteins can produce energy for an organism. a. Which class of substances most rapidly provides energy? b. Which class can be used as a building material in the human body? c. Which is the most efficient as an energy storage system?

In each of the following groups, one of the items does not belong in the group. Identify the odd item in the group and explain why it is different. Explain how the other items are related. a. glycogen, starch, fructose, and cellulose b. amino acids, dipeptides, polypeptides, and proteins c. fats, oils, and fatty acids d. cytosine, adenine, and uracil

Name two examples from each of the following classes of carbohydrates: monosaccharides, disaccharides, and polysaccharides.

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Write a summary discussing what you have learned about the four major classes of organic compounds found in living organisms—carbohydrates, lipids, proteins, and nucleic acids. Include a description of how these organic molecules are used by the body.
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