Question

Write 500 words on the following prompt: You are a scientist who is in charge of a team that is investigating a claim that a very simple form of life has been discovered on another planet. Explain your plan for what you want to learn to perhaps determine if this life form is related to life on Earth, or perhaps it is a unique form of life that evolved independently. You must use and discuss in DETAIL 5 major biochemical or cellular biology concepts in relation to the prompt.

Answer 1

In order to determine the relationship between the life forms on some other planet and Earth, the plan will be to study the genetic material and the Biochemical structure of those organisms. Most of these tests can be conducted on the life forms either alive or dead.

To identify the shared origin of life, following characterictics can be checked and if any or all of these are substantially different, then a separate or independent origin can be concluded.

1. Genetic Code

2. Choice and chirality of amino acids

3. Lipid composition

4. Metabolism

5. Thermodynamics of the living system

Genetic code- It is one of the critical factor that can give a clue of the similarity between these life forms. Identifying the nature of genetic material if its DNA, single or double stranded RNA is the first step follwed by finding out the topology of these forms for eg- A-DNA, Z-DNA or B-DNA. In the life forms on earth, the bases are conserved across life forms i.e. Adenine (A), Guanine (G), Thymine (T) and Cytosine (C) for DNA and Uracil (U) for RNA and stable across the species.

It is necessary to know if it replicates and transmitted to the next generation like that happens on earth. Occurence of repetitive sequences, Variation and formation of secondary structures provide more information regarding it.

Choice and Chiralithy of amino acids- The lego principle can form the basis of a search for biological origins due to the contrast between the selectivity of biology and the nonselectivity of chemistry. Specifically, the concentration of chemically identical molecules might be orders of magnitude variable in a biological sample, whereas similar in a chemical sample. An example of this is the biological selection of L versus D amino acids for proteins by life on Earth. For life on Earth, conservation of the triplet code, the building blocks are the 20 amino acids, the bases A, T, C, G, and U in DNA and RNA, so studying the difference in these can give a lead to understanding evolution.

Lipid compostion- Lipid compostion of any organism depends on the kind of environment where it lives for eg- phospholipid bilayer membrane is present in the living forms staying in the ambient conditions while in archae or extremophiles, phosphodiesters and specific long-chain fatty acids are present in the membrane in order to give them a survival advantage. So, after identifying the atmospheric conditions of that planet, one can predict the features of the lipids present and their possible functions and relation to life forms on earth.

Metabolism - It includes all the chemical reactions performed inside an organism's body essential for survival. In this case, all the enzymes , energy storages like ATP, reducing factors and the modes of waste generation needs to be accessed. Metabolic similarity can provide evidences about the relation between different life forms. General arguments of thermodynamic efficiency and specificity of enzymatic reactions suggest that this selectivity is required for biological function and is a general result of natural selection.

Thermodynamics-  Most life on Earth is dependent on the flow of sunlight, which is utilized by the photosynthetic organisms to construct complex molecules from simpler ones. Certain deep-sea and cave dwelling organisms called chemoautotrophs depend on chemical gradients, such as the natural energy-producing reaction between hydrogen sulfide bubbling up from vents and oxygen dissolved in water. The organization of life on Earth can thus be seen as being driven by a natural second-law-of thermodynamics based reduction between the energy of the hot Sun and the cooler space around it.  

Hence, identifying their mode of obtaining the energy can give information regarding the relation between life forms on earth and other planet.