Science for Thought

Where did life come from?

Where did life come from?

I've discussed this before, but I feel that it needs to be said again with more explanation and pictures.

There are plenty of theories about how life started, including the following theories: it came from Mars (which is called Panspermia), formed in the primordial oceans, came in comets during the late bombardment, drifted here from planets around other stars, or it was delivered by the tooth fairy. Yes, there is evidence of organic molecules in nebulae, accretion discs around proto-stars, and even on moons around the gas giants, but not one of these ideas explains how the main ingredient for life formed, namely DNA.

DNA stands for deoxyribonucleic acid, and it is the cornerstone of life. It makes reproduction possible and every living thing on the planet Earth has it. In fact, parts of our human DNA are in the DNA of plants and insects. This wonderful and truly amazing molecule was found in the single-celled creatures that existed billion of years ago. These single celled creatures evolved into multi-celled creatures and then fish and amphibians that eventually crawled onto land and evolved into us in a very complex manner over hundreds of millions of years, and they brought the DNA with them.
Even if you theorize that early life only had RNA, ribonucleic acid, it's still hard to explain how it came into existence. Just to be sure that you understand how complicated RNA is, I will describe its molecular structure. RNA is a single-stranded, long-chain molecule, unlike DNA, which is a double-stranded molecule. RNA contains ribose, which is a monosaccharide (sugar-like) with five carbon atoms. Basically, it has a pentose structure with an oxygen atom and four carbon atoms in a five-membered ring with hydroxyl groups (OH) hanging off of the carbons. The specific structure is D-ribose because its stereospecific, which means that it's oriented in a specific three-dimensional manner. Now, RNA is actually a sugar formed from ribose connected by phosphate groups. Phosphate groups have four oxygen atoms connected to a phosphorus atom. The pentose groups are connected to two adjacent oxygen atoms by means of removing a hydrogen atom from the hydroxyl groups on the pentose so that the oxygen atoms attached to the pentose ring make up two of the phosphate oxygen atoms. It goes like this: Ribose-O-P-O-Ribose. There are two other oxygen atoms connected to the phosphorus atom. This is how the RNA strand is constructed. Each ribose group can have one of four possible base units attached to one of its ring carbon atoms. These bases are called either pyrimidines or purines and they are complicated structures with nitrogen atoms in a ring structure along with other atoms like oxygen and surfer. The four bases are Adenine, Cytosine, Uracil, and Guanine. The arrangement of these base units determines what proteins the RNA creates after cellular mitoses. RNA can be synthesized but it requires enzymes to accomplish it and it requires DNA as a template.