Enzymes (large molecules) serve to catalyze, or speed up, chemical reactions in the human body. This process of catalysis begins with the binding of a substrate (the reactant) to the active site of an enzyme. This active site is simply the portion of the enzyme that interacts with the substrate. Following the binding event, products separate from the enzyme active site, at which point the enzyme is prepared to undergo another reaction cycle. Two scientists offer conflicting views on the nature of the enzyme-substrate interaction.

Scientist 1

The enzyme-substrate interaction can be modeled with a Lock and Key paradigm. In this model, the enzyme represents a lock and the substrate represents a key. Only the substrate of proper size and shape will fit into a particular enzyme's active site and catalyze the reaction. The enzyme-substrate complex, the intermediate of this reaction, is stabilized mostly by strong ionic and hydrogen bonds. Following the formation of this intermediate, the enzyme changes the substrate in some way, leading to formation of a product, which subsequently dissociates from the enzyme.

Scientist 2

The shapes of substrate and enzyme are not exactly complementary. When it binds to the enzyme, the substrate induces the active site to alter its shape in order to enhance the fit. Thus, at first the interaction between substrate and enzyme is weak, but subsequent changes in the active site lead to stronger binding. Only the correct substrate will be able to modify the active site in the proper manner. Experimental data seems consistent with this Induced Fit model and inconsistent with the Lock and Key model.

For a certain enzyme that is also a protein, it is observed that the amino acids (building blocks of a protein) near the active site move immediately after the substrate binds. Is this observation consistent with the viewpoint of Scientist 1?

Enzymes (large molecules) serve to catalyze, or speed up, chemical reactions in the human body. This process of catalysis begins with the binding of a substrate (the reactant) to the active site of an enzyme. This active site is simply the portion of the enzyme that interacts with the substrate. Following the binding event, products separate from the enzyme active site, at which point the enzyme is prepared to undergo another reaction cycle. Two scientists offer conflicting views on the nature of the enzyme-substrate interaction.

Scientist 1

The enzyme-substrate interaction can be modeled with a Lock and Key paradigm. In this model, the enzyme represents a lock and the substrate represents a key. Only the substrate of proper size and shape will fit into a particular enzyme's active site and catalyze the reaction. The enzyme-substrate complex, the intermediate of this reaction, is stabilized mostly by strong ionic and hydrogen bonds. Following the formation of this intermediate, the enzyme changes the substrate in some way, leading to formation of a product, which subsequently dissociates from the enzyme.

Scientist 2

The shapes of substrate and enzyme are not exactly complementary. When it binds to the enzyme, the substrate induces the active site to alter its shape in order to enhance the fit. Thus, at first the interaction between substrate and enzyme is weak, but subsequent changes in the active site lead to stronger binding. Only the correct substrate will be able to modify the active site in the proper manner. Experimental data seems consistent with this Induced Fit model and inconsistent with the Lock and Key model.

With which of the following statements would both Scientist 1 and Scientist 2 most likely agree?

Enzymes (large molecules) serve to catalyze, or speed up, chemical reactions in the human body. This process of catalysis begins with the binding of a substrate (the reactant) to the active site of an enzyme. This active site is simply the portion of the enzyme that interacts with the substrate. Following the binding event, products separate from the enzyme active site, at which point the enzyme is prepared to undergo another reaction cycle. Two scientists offer conflicting views on the nature of the enzyme-substrate interaction.

Scientist 1

The enzyme-substrate interaction can be modeled with a Lock and Key paradigm. In this model, the enzyme represents a lock and the substrate represents a key. Only the substrate of proper size and shape will fit into a particular enzyme's active site and catalyze the reaction. The enzyme-substrate complex, the intermediate of this reaction, is stabilized mostly by strong ionic and hydrogen bonds. Following the formation of this intermediate, the enzyme changes the substrate in some way, leading to formation of a product, which subsequently dissociates from the enzyme.

Scientist 2

The shapes of substrate and enzyme are not exactly complementary. When it binds to the enzyme, the substrate induces the active site to alter its shape in order to enhance the fit. Thus, at first the interaction between substrate and enzyme is weak, but subsequent changes in the active site lead to stronger binding. Only the correct substrate will be able to modify the active site in the proper manner. Experimental data seems consistent with this Induced Fit model and inconsistent with the Lock and Key model.

The active site of an enzyme has a volume of about  cubic angstroms ( angstrom equals  meter). Assuming that Scientist 2 is correct, how would the active site change if a substrate of about  cubic angstroms were to bind the enzyme?

The electrons of an atom surround the nucleus and reside in atomic orbitals. In transition metals such as iron () and cobalt (), the outermost electrons reside in  orbitals. For a free metal, these  orbitals are equal in energy.  However, as soon as ligands (molecules or ions) bind the metal, the metal  orbitals split in energy (Figure 1).

Scientists perform a number of experiments to determine how various factors affect the magnitude of splitting. They find that the charge on the metal, the metal's position on the periodic table (whether it resides in Period 4, 5, or 6), and the identity of the ligand are all important factors. The scientists' results are summarized in Table 1. Note that a higher value of  indicates larger splitting.

Table 1

Consider Table 1. Which of the following factors differed between Trial 1 and Trial 3?

The electrons of an atom surround the nucleus and reside in atomic orbitals. In transition metals such as iron () and cobalt (), the outermost electrons reside in  orbitals. For a free metal, these  orbitals are equal in energy.  However, as soon as ligands (molecules or ions) bind the metal, the metal  orbitals split in energy (Figure 1).

Scientists perform a number of experiments to determine how various factors affect the magnitude of splitting. They find that the charge on the metal, the metal's position on the periodic table (whether it resides in Period 4, 5, or 6), and the identity of the ligand are all important factors. The scientists' results are summarized in Table 1. Note that a higher value of  indicates larger splitting.

Table 1

Which compounds illustrate the relationship between position of a metal on the periodic table and splitting magnitude?

The electrons of an atom surround the nucleus and reside in atomic orbitals. In transition metals such as iron () and cobalt (), the outermost electrons reside in  orbitals. For a free metal, these  orbitals are equal in energy.  However, as soon as ligands (molecules or ions) bind the metal, the metal  orbitals split in energy (Figure 1).

Scientists perform a number of experiments to determine how various factors affect the magnitude of splitting. They find that the charge on the metal, the metal's position on the periodic table (whether it resides in Period 4, 5, or 6), and the identity of the ligand are all important factors. The scientists' results are summarized in Table 1. Note that a higher value of  indicates larger splitting.

Table 1

The coordination number of a compound refers to the number of ligands attached to the central metal atom (All compounds listed in Table 1 have coordination number of 6). Given that a lower coordination number tends to result in a smaller splitting magnitude, which of the following could be the splitting magnitude of , which has a coordination number of 4 and a charge of +2? 

Kevin wants to know if a particular kind of chemical fertilizer will help or hinder the growth of his tomato plants. He decides to conduct an experiment in which he grows three plants, one left untreated, one treated with the chemical fertilizer RapidGro and one treated with an organic compost. He records his findings in the charts below, measuring plant height and number of tomatoes over a period of time.

Height of plant (inches):

Number of tomatoes:

On the fourteenth day Kevin picks the biggest tomato from each plant and record its dimensions, as well as other information, which is found below.

Tomato 1 (no fertilizer):  in diameter, dull red, lumpy in shape, wormholes, flavorful.

Tomato 2 (RapidGro):  in diameter, shiny red, round, somewhat tasteless.

Tomato 3 (compost):  in diameter, deep red, lumpy shape, very flavorful.

What might make it difficult for Kevin to draw a conclusion about the plants?

Kevin wants to know if a particular kind of chemical fertilizer will help or hinder the growth of his tomato plants. He decides to conduct an experiment in which he grows three plants, one left untreated, one treated with the chemical fertilizer RapidGro and one treated with an organic compost. He records his findings in the charts below, measuring plant height and number of tomatoes over a period of time.

Height of plant (inches):

Number of tomatoes:

On the fourteenth day Kevin picks the biggest tomato from each plant and record its dimensions, as well as other information, which is found below.

Tomato 1 (no fertilizer):  in diameter, dull red, lumpy in shape, wormholes, flavorful.

Tomato 2 (RapidGro):  in diameter, shiny red, round, somewhat tasteless.

Tomato 3 (compost):  in diameter, deep red, lumpy shape, very flavorful.

What could have happened to plant 2 between days 10 and 14?

Kevin wants to know if a particular kind of chemical fertilizer will help or hinder the growth of his tomato plants. He decides to conduct an experiment in which he grows three plants, one left untreated, one treated with the chemical fertilizer RapidGro and one treated with an organic compost. He records his findings in the charts below, measuring plant height and number of tomatoes over a period of time.

Height of plant (inches):

Number of tomatoes:

On the fourteenth day Kevin picks the biggest tomato from each plant and record its dimensions, as well as other information, which is found below.

Tomato 1 (no fertilizer):  in diameter, dull red, lumpy in shape, wormholes, flavorful.

Tomato 2 (RapidGro):  in diameter, shiny red, round, somewhat tasteless.

Tomato 3 (compost):  in diameter, deep red, lumpy shape, very flavorful.

What information might have been helpful to Kevin while gathering his data?

Kevin wants to know if a particular kind of chemical fertilizer will help or hinder the growth of his tomato plants. He decides to conduct an experiment in which he grows three plants, one left untreated, one treated with the chemical fertilizer RapidGro and one treated with an organic compost. He records his findings in the charts below, measuring plant height and number of tomatoes over a period of time.

Height of plant (inches):

Number of tomatoes:

On the fourteenth day Kevin picks the biggest tomato from each plant and record its dimensions, as well as other information, which is found below.

Tomato 1 (no fertilizer):  in diameter, dull red, lumpy in shape, wormholes, flavorful.

Tomato 2 (RapidGro):  in diameter, shiny red, round, somewhat tasteless.

Tomato 3 (compost):  in diameter, deep red, lumpy shape, very flavorful.

Which of the following are not true?