In 1953, Stanley Miller and Harold Urey performed an experiment at the University of Chicago to test the hypothesis that the conditions of the early Earth would have favored the formation of larger, more complex organic molecules from basic precursors. The experiment, as shown below, consisted of sealing basic organic chemicals (representing the atmosphere of the primitive Earth) in a flask, which was exposed to electric sparks (to simulate lightning) and water vapor. After one day of exposure, the mixture in the flask had turned pink in color, and later analysis showed that at least \(10 \%\) of the carbon had been transformed into simple and complex organic compounds including at least 11 different amino acids and some basic sugars. No nucleic acids were detected in the mixture. .Some amino acids, such as cysteine (shown below) and methionine, could not be formed in this experiment.Which of the following best explains why these molecules could not be detected? (A) The chemical reactions necessary to create amino acids such as cysteine and methionine require more energy than the simulated lightning provided in the experiment. (B) The chemical reactions necessary to create amino acids such as cysteine and methionine require enzymes for catalysis to occur, which were not included in the experiment. (C) Sulfur-based compounds were not included in the experiment. (D) Nitrogen-based compounds were not included in the experiment.

Step by step solution

01

Understanding the Miller-Urey Experiment

Here, the Miller-Urey experiment aimed to simulate the early Earth conditions by providing basic organic chemicals representing the atmosphere, electric sparks simulating lightning, and water vapor. The formation of various organic compounds, including amino acids and basic sugars, was observed in the experiment. However, some amino acids, such as cysteine and methionine, were not detected in the mixture formed in the experiment.

02

Analyzing each option given

We will now analyze each option with respect to the experiment and the formation of amino acids, particularly cysteine and methionine. (A) Insufficient energy provided by simulated lightning: While lightning sparks do provide energy for chemical reactions, there is no specific mention or indication that the energy provided in the experiment was insufficient for certain amino acids' formation. (B) Requirement of enzymes for catalysis: Enzymes are biological catalysts, but they are not the only catalysts available. In the context of the Miller-Urey experiment, having enzymes is unnecessary for explaining the non-formation of particular amino acids. (C) Absence of sulfur-based compounds in the experiment: Cysteine and methionine are sulfur-containing amino acids. If sulfur-based compounds were not present in the initial precursor mixture, then these amino acids would not be formed as a result of the experiment. (D) Absence of nitrogen-based compounds in the experiment: Nitrogen-based compounds are an important part of amino acids, but their absence would indicate the incomplete formation of every amino acid, not just cysteine and methionine specifically.

03

Selecting the best explanation

Comparing the given options, (C) Sulfur-based compounds were not included in the experiment, is the best explanation for why cysteine and methionine could not be detected in the mixture.

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