Читать книгу Astrobiology - Charles S. Cockell - Страница 99

We now have a good idea of how elements are assembled into atoms and how atoms form molecules and then the major classes of macromolecules from which life is constructed. The next stage of this journey must be to consider how these macromolecules are assembled into self-replicating living cells. From this point, we can go on to consider how these cells diversified into the array of life that we witness on Earth today, how this has changed over time, and whether this might have occurred, or be occurring, on other planetary bodies in the Universe. This chapter is concerned with understanding how macromolecules are assembled into the cells of life.

An understanding of cellular structure and the components of cells has application across diverse areas of astrobiology:

1 To investigate the origin of life, we need to know the minimum requirements for a reproducing cellular entity.

2 To be able to infer what the characteristics of the earliest types of cell were, we need to understand the structure of life today.

3 The search for life elsewhere in the Universe is strongly predicated on our knowledge of cellular structure. For example, if we want to look for remnant biological matter on Mars to test the hypothesis that the planet hosted life, we need to know what parts of cells might preserve well. That line of enquiry begins with an understanding of cellular structure.

4 From a less applied perspective, we could return to the question of whether the structure of biological material on Earth is universal. If biological evolution has occurred on another planet, would it produce the same sorts of structures we see in life on Earth? This question is difficult to address without another example of life to study, but we can only begin to embark on considering this question with a good knowledge of the structure of life on Earth.

From many perspectives, a grasp of cellular structure and how the individual components of cells come together to form a single cell is important. An understanding of cellular structure and its relevance to astrobiology is the focus of this chapter.