Question

The proposed primordial soup was composed of organic precursor molecules formed by interactions between all the following gases EXCEPT A. oxygen and hydrogen. B. helium. C. nitrogen. D. carbon.

Short answer

B. helium.

Step-by-step solution

- Understanding the Concept of Primordial Soup

The primordial soup theory suggests that life began in a body of water with a mixture of organic compounds. These compounds formed through chemical reactions involving gases present in the Earth's early atmosphere.

- Identifying Relevant Gases

Consider the gases involved in forming organic precursor molecules: oxygen (O₂), hydrogen (H₂), nitrogen (N₂), and carbon (C) compounds (like methane or carbon dioxide).

- Considering Helium's Role

Helium (He) is a noble gas and chemically inert. It does not easily form compounds and would not contribute to chemical reactions forming organic precursor molecules.

- Eliminating the Correct Answer

Since helium does not participate in forming organic compounds, it is the correct answer to the question about which gas was NOT involved in the primordial soup.

Key concepts

organic precursor molecules

Organic precursor molecules are the basic building blocks of life. These molecules include amino acids, nucleotides, and simple carbohydrates. These molecules can combine and re-combine in various ways to form more complex structures like proteins, DNA, and RNA. According to the primordial soup theory, these molecules formed in the early Earth's oceans through a series of chemical reactions. These reactions were driven by sources of energy like UV radiation, lightning, and volcanic activity. Without these organic precursor molecules, the complex chemistry of life could not begin.

• Amino acids: They are the building blocks of proteins, which are essential for life's functions.
• Nucleotides: These are the building blocks of DNA and RNA, which store and transmit genetic information.
• Carbohydrates: Simple sugars that provide energy and structural components in cells.

The presence of these organic precursor molecules in the primordial soup is crucial for the development of life on Earth.

early Earth's atmosphere

The early Earth's atmosphere was very different from what we have today. It was composed of gases like methane (CH₄), ammonia (NH₃), hydrogen (H₂), and water vapor (H₂O). There was very little to no oxygen (O₂) present. This reducing atmosphere was essential for the formation of organic precursor molecules.

• Methane (CH₄): Provides carbon, a key element in organic compounds.
• Ammonia (NH₃): Provides nitrogen, another essential element for life.
• Hydrogen (H₂): A primary reducing agent that facilitates chemical reactions.
• Water vapor (H₂O): The medium in which these reactions occurred.

This unique composition allowed chemical reactions to take place, leading to the formation of life-building molecules. The absence of oxygen was crucial because oxygen tends to break down complex organic molecules, making it less likely for them to form.

chemical reactions

Chemical reactions are processes where substances combine or break apart to form new substances. In the context of the primordial soup theory, these reactions were essential for forming organic precursor molecules. Energy sources like lightning and UV radiation provided the necessary activation energy for these reactions.
These reactions involved simple molecules and gases from the early Earth's atmosphere. For example, methane and ammonia could react in the presence of hydrogen to form amino acids and other organic compounds. Such reactions are significant because they create the building blocks necessary for more complex forms of life.

• Combination Reactions: Where two or more substances combine to form a new compound.
• Decomposition Reactions: Where a compound breaks down into simpler substances.
• Redox Reactions: Involves the transfer of electrons between substances, crucial for metabolic processes.

Understanding these basic chemical reactions helps us comprehend how life could originate from non-living matter in the primordial soup.