Why are proteins not considered to be a good candidate for the first living molecule? a. Their catalytic capability is not sufficient for most biological reactions. b. Their amino acid monomers were not likely present in the prebiotic soup. c. They cannot serve as a template for replication. d. They could not have polymerized from amino acid monomers under early Earth conditions.

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1. Proteins are not considered to be a good candidate for the first living molecule primarily because they cannot serve as a template for replication. This is crucial for the propagation and evolution of early life forms.
2. The ability to serve as a template for replication is essential for the transmission of genetic information from one generation to the next, a fundamental property of life.
3. Nucleic acids like RNA and DNA, unlike proteins, can serve as templates. They can replicate themselves through base pairing mechanisms, where each strand can serve as a template for the formation of a complementary strand.
4. Proteins, made up of amino acids, do not have the capability to form such complementary pairs that are necessary for self-replication.
5. Therefore, while proteins are crucial for various structural and enzymatic functions in current life forms, their inability to replicate independently makes them unlikely candidates for the first living molecules.

Key Concepts

Catalytic Capability of Proteins

Proteins, while they can act as enzymes to catalyze biochemical reactions, often require specific conditions and cofactors to function effectively. In the context of early Earth, the complexity and specificity of protein catalysts may not have been sufficient to drive the necessary reactions for the origin of life, making them less likely candidates for the first living molecules.

Prebiotic Soup and Amino Acids

The prebiotic soup hypothesis suggests that the early Earth contained a mixture of organic compounds, including amino acids, which are the building blocks of proteins. However, the specific amino acids required to form functional proteins may not have been present in sufficient quantities or diversity in this primordial environment, limiting the potential for proteins to emerge as the first living molecules.

Template for Replication

For a molecule to be considered a candidate for the first living entity, it must possess the ability to replicate itself. Proteins do not have the inherent capability to serve as templates for their own synthesis, unlike nucleic acids such as RNA, which can store genetic information and replicate, making proteins less suitable as the first living molecules.