Which of the following steps has not yet been accomplished by scientists studying the origin of life?
a. Synthesis of small RNA polymers by ribozymes
b. Formation of molecular aggregates with selectively permeable membranes
c. Formation of protocells that use DNA to direct the polymerization of amino acids
d. Abiotic synthesis of organic molecules

Verified step by step guidance

1. Understand the context of the problem: Scientists studying the origin of life are trying to recreate the conditions and processes that could have led to the formation of life on Earth. This involves several key steps, including the synthesis of organic molecules, formation of protocells, and the development of genetic material.
2. Review each option to determine what has been accomplished: Option (a) refers to the synthesis of small RNA polymers by ribozymes, which has been demonstrated in laboratory settings. Ribozymes are RNA molecules that can catalyze chemical reactions, including the formation of RNA strands.
3. Consider option (b): Formation of molecular aggregates with selectively permeable membranes has been achieved. Scientists have created vesicles or liposomes that mimic cell membranes, allowing selective passage of substances, which is a crucial step in forming protocells.
4. Evaluate option (c): Formation of protocells that use DNA to direct the polymerization of amino acids is a more complex step. While protocells have been created, the integration of DNA to direct protein synthesis is a significant leap that has not been fully realized in experimental settings.
5. Assess option (d): Abiotic synthesis of organic molecules has been accomplished, as demonstrated by experiments like the Miller-Urey experiment, which showed that simple organic compounds could be formed from inorganic precursors under prebiotic conditions.

Key Concepts

Abiotic Synthesis of Organic Molecules

Abiotic synthesis refers to the formation of organic molecules without the involvement of living organisms. This process is crucial in theories about the origin of life, suggesting that simple organic compounds could form under prebiotic conditions, such as in the primordial soup or on early Earth, providing the building blocks for more complex molecules.

Ribozymes and RNA World Hypothesis

Ribozymes are RNA molecules capable of catalyzing specific biochemical reactions, similar to protein enzymes. The RNA world hypothesis posits that self-replicating ribozymes were crucial in early life forms, potentially leading to the synthesis of small RNA polymers. This concept supports the idea that RNA could have been the first genetic material, preceding DNA and proteins in evolutionary history.

Protocells and Selectively Permeable Membranes

Protocells are simple, cell-like structures that exhibit some properties of living cells, such as a selectively permeable membrane. These structures are thought to have played a role in the origin of life by providing a controlled environment for chemical reactions. The formation of protocells is a key step in understanding how non-living chemical compounds could transition into living organisms.