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Biological Sciences

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Enzymes and Energy

Question
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In general, enzymes are protein molecules which must be folded in a specific three-dimensional shape in order to function properly. Certain environmental parameters can affect enzyme activity, including pH and temperature. If an enzyme’s shape changes significantly and it can no longer function, the enzyme is said to have become denatured.

The enzyme pancreatic amylase is manufactured and secreted by the pancreas into the duodenum (the large, beginning portion of the small intestine). Pancreatic amylase breaks down starch into maltose, a disaccharide. Pepsin is an enzyme that is released by the epithelium of the stomach, and functions in the stomach to break down proteins into smaller polypeptide units.

The following graphs show the activities of various enzymes under various environmental conditions.

Graph 1:

Graph 2:


Which of the following statements is true with respect to graph 1?

A Pepsin and pancreatic amylase could never function together in the same part of the body at the same time.
B Pancreatic amylase could function in the stomach, but its activity would be low.
C The optimal pH for the functioning of pepsin is approximately 8.5.
D Normally, the small intestine must be slightly acidic.
Ans. A

We can tell that this is true because the ranges of activity depicted by the graph do not overlap. Therefore, no pH value exists at which both enzymes will be even slightly active. It is assumed that the general pH values are known for the stomach and small intestine, approximately 2 and 8 respectively. Therefore, the graph confirms that pancreatic amylase will have no activity at pH 2 (choice B), but that this is the optimum for pepsin (not 8.5, as is suggested in choice C.) The graph additionally shows that pancreatic amylase loses all activity at pH 7, so that it could not function in an acidic environment. Since the passage tells us that pancreatic amylase functions in the small intestine, choice D must be incorrect.

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.