Polarity Enzyme Skills Worksheet
ANALYZING INFORMATION/INTERPRETING GRAPHICS
Dirt sticks to the body either by becoming trapped in microscopic wrinkles in the skin or, if the dirt is moist, by adhering to the body. Sometimes the natural oils on skin will give the dirt an oily coating. In such cases, water alone will not remove the dirt, but soap and water will. Use the information below and your understanding of polarity and chemical bonding to answer questions 1 –3.
A. A soap molecule is long, with one end attracted to oil molecules.
B. One end of a soap molecule is polar, and the other end is nonpolar.
C. Soap will dissolve, and the soap molecules will float freely in water.
D. A sewing needle will rest upon the surface of water. If powdered soap is gently sprinkled near the needle, the needle will eventually sink.
Read each question, and write your answer in the space provided.
1. Explain why adding soap to water will help remove dirt and oil.
Soap has one end (the non-polar end) that is attracted to oil, so w hen it’s dissolved in water any dirt there will be stuck to soap. The other part of soap will be attracted to the polar water molecules, creating microscopic bubbles of soap-covered oil. This can be washed away.
2. Why does the needle float on the water?
Water has high surface tension. This surface tension is stronger than the pull of gravity on a light needle. The needle floats as a result.
3. Why does the needle sink after soap is added to the water?
Polar molecules, like soap (at least part of it), will disrupt the cohesion between water molecules and cause surface tension to be reduced past the point where the pull of gravity will be greater than the interrupted pull of cohesion.
The graph below shows the rate of enzyme activity in relation to pH for two enzymes —pepsin and trypsin. Both enzymes break down molecules in food taken into the human body, but the enzymes act in series. Pepsin breaks some bonds in very large molecules. Trypsin acts on the fragments produced by the action of pepsin, breaking them into even smaller units. Use the graph to answer questions 4 –8.
Read each question, and write your answer in the space provided.
4. The liquid in the stomach has a pH of about 2.
Which of the two enzymes would be active in the stomach?
Pepsin and not trypsin.
5. The liquid in the small intestine has a pH of about 8. Which of the two enzymes would be active in the small intestine?
Trypsin and not pepsin.
6. What must happen to the liquid as it passes from the stomach to the small intestine for digestion to occur normally?
The pH must change to match that of the small intestine.
7. Consider the data on the relationship between pH and enzyme activity shown in the graph. Do enzymes typically function only at a specific pH, or can they function within a range of pH values?
They can operate within a range of pH’s, but they obviously operate most efficiently at optimal pH’s.
8. Can pepsin and trypsin function in the same environment? Explain.
Technically, they can function in between pH’s of 4 & 5.

9. Which of the following is a characteristic of enzymes? a. The lower the energy of activation of a reaction by binding the substrate b. They raise the energy of activation of a reaction by binding the substrate c. They lower the amount of energy present in the substrate d. They raise the amount of energy present in the substrate
10. Which of the following does not apply to the functionality of enzymes? a. Enzymes lower activation energy required to convert substrates to products. b. Enzymes are consumed in a chemical reaction. c. Enzymes are specific to a particular reaction. d. Enzymes act to speed up chemical reactions
11. The effect of temperature on the relative rate of action of an enzyme is represented in the graph below.
12. What is the optimum temperature for the action of this enzyme? ______________________ a. 0°C c. 30°C b. 40°C d. 58°C
13. Out of the four things listed what will most likely not affect an enzyme? a. Temperature c. Salt b. pH d. H
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14. Which statement describes the currently accepted theory of how an enzyme and its substrate fit together? a. As the product is released, the enzyme breaks down b. The reactants are like a key that fits into the enzyme, which is like a lock. c. The active site is permanently changed by its interaction with the substrate. d. As any substrate binds to an enzyme, the shape of the active site changes to accommodate the reaction