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Biological Sciences

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Enzymes and Energy

Question
7 out of 10
 

The reagent iodine potassium iodide (IKI) can be used to detect the presence of starch in a solution. IKI is normally light yellow in color; in the presence of starch it turns a deep blue. IKI can therefore be used to test for the presence and activity of the enzyme amylase, which breaks starch into maltose disaccharide units. (Maltose does not affect the color of IKI). Thus, if starch is initially present and mixed with IKI, the deep blue color created will begin to lighten and disappear if amylase is present as it begins to break down the starch to maltose. Using the same concentration of enzyme, the longer it takes for the blue color to disappear, the lower the amylase activity.

Amylase is usually present in vertebrates in two forms that work in different parts of the digestive tract. Salivary amylase, secreted in the saliva by the salivary glands, begins to break down starch in the mouth, which has a slightly acidic pH. Pancreatic amylase is manufactured by the pancreas and released into the small intestine, where it similarly breaks down remaining starch molecules to maltose.

The following tables show the results of an experiment designed to test the activities of one form of amylase at various pH’s and temperatures.

pH

Time for blue color to disappear (in minutes)

3

10

6

1

9

5

12

30

Temperature (˚C)

Time for blue color to disappear (minutes)

15

10

30

5

37

1

60

blue color never disappears


What is the most likely explanation for the observation that the blue color never disappears at 60˚ C?

A The chemical bonds in starch are stabilized by the heat so that it cannot break down even though the enzyme is highly active.
B Heat causes the IKI to become unable to stain the starch.
C The amylase has become denatured at this temperature.
D All of the above are reasonable explanations.
Ans. C

A human enzyme would likely become denatured at 600 C, as we saw in the last passage, and this would account for the lack of activity (the failure of the blue color to disappear implies that the starch remains present forever, since the enzyme cannot break it down). Choice A does not make sense, since heat will always tend to destabilize chemical bonds. Choice B could not be correct, because the IKI is still active; it is responsible for the blue color. Logically, this leaves out choice D, too.

Enzymes and Energy Flashcard List

10 flashcards
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The reagent iodine potassium iodide (IKI) can be used to detect the presence of starch in a solution. IKI is normally light yellow in color; in the presence of starch it turns a deep blue. IKI can therefore be used to test for the presence and activity of the enzyme amylase, which breaks starch into maltose disaccharide units. (Maltose does not affect the color of IKI). Thus, if starch is initially present and mixed with IKI, the deep blue color created will begin to lighten and disappear if amylase is present as it begins to break down the starch to maltose. Using the same concentration of enzyme, the longer it takes for the blue color to disappear, the lower the amylase activity. Amylase is usually present in vertebrates in two forms that work in different parts of the digestive tract. Salivary amylase, secreted in the saliva by the salivary glands, begins to break down starch in the mouth, which has a slightly acidic pH. Pancreatic amylase is manufactured by the pancreas and released into the small intestine, where it similarly breaks down remaining starch molecules to maltose. The following tables show the results of an experiment designed to test the activities of one form of amylase at various pH’s and temperatures. pH Time for blue color to disappear (in minutes) 3 10 6 1 9 5 12 30 Temperature (˚C) Time for blue color to disappear (minutes) 15 10 30 5 37 1 60 blue color never disappears Which of the following is the enzyme being tested?A Human salivary amylaseB Shark salivary amylaseC Human pancreatic amylaseD Shark pancreatic amylase
7)
The reagent iodine potassium iodide (IKI) can be used to detect the presence of starch in a solution. IKI is normally light yellow in color; in the presence of starch it turns a deep blue. IKI can therefore be used to test for the presence and activity of the enzyme amylase, which breaks starch into maltose disaccharide units. (Maltose does not affect the color of IKI). Thus, if starch is initially present and mixed with IKI, the deep blue color created will begin to lighten and disappear if amylase is present as it begins to break down the starch to maltose. Using the same concentration of enzyme, the longer it takes for the blue color to disappear, the lower the amylase activity. Amylase is usually present in vertebrates in two forms that work in different parts of the digestive tract. Salivary amylase, secreted in the saliva by the salivary glands, begins to break down starch in the mouth, which has a slightly acidic pH. Pancreatic amylase is manufactured by the pancreas and released into the small intestine, where it similarly breaks down remaining starch molecules to maltose. The following tables show the results of an experiment designed to test the activities of one form of amylase at various pH’s and temperatures. pH Time for blue color to disappear (in minutes) 3 10 6 1 9 5 12 30 Temperature (˚C) Time for blue color to disappear (minutes) 15 10 30 5 37 1 60 blue color never disappears What is the most likely explanation for the observation that the blue color never disappears at 60˚ C?A The chemical bonds in starch are stabilized by the heat so that it cannot break down even though the enzyme is highly active.B Heat causes the IKI to become unable to stain the starch.C The amylase has become denatured at this temperature.D All of the above are reasonable explanations.
8)
The reagent iodine potassium iodide (IKI) can be used to detect the presence of starch in a solution. IKI is normally light yellow in color; in the presence of starch it turns a deep blue. IKI can therefore be used to test for the presence and activity of the enzyme amylase, which breaks starch into maltose disaccharide units. (Maltose does not affect the color of IKI). Thus, if starch is initially present and mixed with IKI, the deep blue color created will begin to lighten and disappear if amylase is present as it begins to break down the starch to maltose. Using the same concentration of enzyme, the longer it takes for the blue color to disappear, the lower the amylase activity. Amylase is usually present in vertebrates in two forms that work in different parts of the digestive tract. Salivary amylase, secreted in the saliva by the salivary glands, begins to break down starch in the mouth, which has a slightly acidic pH. Pancreatic amylase is manufactured by the pancreas and released into the small intestine, where it similarly breaks down remaining starch molecules to maltose. The following tables show the results of an experiment designed to test the activities of one form of amylase at various pH’s and temperatures. pH Time for blue color to disappear (in minutes) 3 10 6 1 9 5 12 30 Temperature (˚C) Time for blue color to disappear (minutes) 15 10 30 5 37 1 60 blue color never disappears What is the optimal temperature and pH for the enzyme being tested?A 15˚ C, pH 12B 37˚ C, pH 6C 37˚ C, pH 12D 15˚ C, pH 6
9)
The reagent iodine potassium iodide (IKI) can be used to detect the presence of starch in a solution. IKI is normally light yellow in color; in the presence of starch it turns a deep blue. IKI can therefore be used to test for the presence and activity of the enzyme amylase, which breaks starch into maltose disaccharide units. (Maltose does not affect the color of IKI). Thus, if starch is initially present and mixed with IKI, the deep blue color created will begin to lighten and disappear if amylase is present as it begins to break down the starch to maltose. Using the same concentration of enzyme, the longer it takes for the blue color to disappear, the lower the amylase activity. Amylase is usually present in vertebrates in two forms that work in different parts of the digestive tract. Salivary amylase, secreted in the saliva by the salivary glands, begins to break down starch in the mouth, which has a slightly acidic pH. Pancreatic amylase is manufactured by the pancreas and released into the small intestine, where it similarly breaks down remaining starch molecules to maltose. The following tables show the results of an experiment designed to test the activities of one form of amylase at various pH’s and temperatures. pH Time for blue color to disappear (in minutes) 3 10 6 1 9 5 12 30 Temperature (˚C) Time for blue color to disappear (minutes) 15 10 30 5 37 1 60 blue color never disappears The breakdown of starch is an exergonic reaction, which would occur spontaneously at temperatures of about 200˚ C. Amylase allows the reaction to proceed at physiological temperatures by:A Increasing the activation energy for the reaction.B Increasing the potential energy of the reactants.C Changing the amount of energy released by the reaction.D Lowering the activation energy of the reaction.
10)
The reagent iodine potassium iodide (IKI) can be used to detect the presence of starch in a solution. IKI is normally light yellow in color; in the presence of starch it turns a deep blue. IKI can therefore be used to test for the presence and activity of the enzyme amylase, which breaks starch into maltose disaccharide units. (Maltose does not affect the color of IKI). Thus, if starch is initially present and mixed with IKI, the deep blue color created will begin to lighten and disappear if amylase is present as it begins to break down the starch to maltose. Using the same concentration of enzyme, the longer it takes for the blue color to disappear, the lower the amylase activity. Amylase is usually present in vertebrates in two forms that work in different parts of the digestive tract. Salivary amylase, secreted in the saliva by the salivary glands, begins to break down starch in the mouth, which has a slightly acidic pH. Pancreatic amylase is manufactured by the pancreas and released into the small intestine, where it similarly breaks down remaining starch molecules to maltose. The following tables show the results of an experiment designed to test the activities of one form of amylase at various pH’s and temperatures. pH Time for blue color to disappear (in minutes) 3 10 6 1 9 5 12 30 Temperature (˚C) Time for blue color to disappear (minutes) 15 10 30 5 37 1 60 blue color never disappears Which of the following statements is true of the action of amylase at its optimum pH and temperature?A The enzyme is irreversibly changed, so that one enzyme molecule can only catalyze the reaction once.B It is denatured, and the enzyme’s activity is the highest possible.C The active site of amylase consists of every amino acid in the protein.D This pH and temperature represents the physiological conditions under which it functions in nature.