Definition
A nucleic acid is a strand of nucleotides that stores information genetic in biological systems. It creates DNA and RNA, which store the information that cells need to make proteins. This information is stored in multiple sets of three nucleotides, known as codons.
How nucleic acids work
The name comes from the fact that these molecules are acids, i.e. they are good at donating protons and accepting electron pairs in chemical reactions, and the fact that they were first discovered in the nuclei of our cells.
Generally, a nucleic acid is a molecule a large molecule made up of a chain or “polymer” of units called “nucleotides”. All life on Earth uses nucleic acids as a means of recording hereditary information, i.e., nucleic acids are the hard drives that contain the essential blueprint or “source code” for creating cells.
For many years, scientists wondered how living things “knew” how to produce all the complex materials they need to grow and survive, and how they passed on their traits to their offspring.
Scientists finally found the answer in the form of DNA, deoxyribonucleic acid, a molecule located in the nucleus of the cells, which was passed on from the mother cells to the “daughter” cells.
When the DNA was damaged or passed on incorrectly, scientists discovered that the cells would not function properly. DNA damage would cause cells and organisms to develop incorrectly, or to be so badly damaged that they simply died.
Later experiments revealed that another type of nucleic acid, RNA or ribonucleic acid, acted as a “messenger” that could carry copies of the instructions found in DNA. Ribonucleic acid was also used to pass on instructions from generation to generation by some viruses.
Function of nucleic acids
Nucleic acids store information like computer code.
By far the most important function of nucleic acids for living things is their role as carriers of information.
Because nucleic acids can be created with four “bases” and because “base pairing rules” allow information to be “copied” using one strand of nucleic acids as a template to create another, these molecules can contain and copy information.
To understand this process, it may be useful to compare the DNA code with the binary code used by computers. The two codes are very different in their details, but the principle is the same. Just as your computer can create complete virtual realities simply by reading strings of 1’s and 0’s, cells can create complete living organisms by reading strings of the four base pairs of DNA.
As you can imagine, without binary code, you would have no computer and no computer programs. In the same way, living organisms need intact copies of their DNA “source code” to function.
The parallels between the genetic code and binary code have even led some scientists to propose the creation of “genetic computers”, which could store information far more efficiently than hard drives based on silicon. However, as our ability to record information in silicon has advanced, little attention has been paid to research into “genetic computers”.
Information protection
Because the source code of DNA is so vital to an organisation’s cell Like your operating system for your computer, DNA must be protected from damage. To transport the DNA’s instructions to other parts of the cell, copies of its information are made using another type of nucleic acid: RNA.
It is these RNA copies of genetic information that are sent out of the nucleus and around the cell to be used as instructions by the cellular machinery.
Cells also use nucleic acids for other purposes. Ribosomes, the cellular machines that produce proteins, and some enzymes are made of RNA.
DNA uses RNA as a species protective mechanism, which separates the DNA from the chaotic environment of the cytoplasm. Inside the nucleus, DNA is protected. Outside the nucleus, movements of organelles, vesicles and other cellular components could easily damage the long, complex DNA strands.
The fact that RNA can act both as hereditary material and as an enzyme reinforces the idea that the first life could have been a self-replicating, self-catalysing RNA molecule.
Examples of nucleic acids
The most common nucleic acids in nature are DNA and RNA. These molecules form the basis of most life on Earth and store the information needed to create proteins that, in turn, complete the functions necessary for cells to survive and reproduce. However, DNA and RNA are not the only nucleic acids. However, artificial nucleic acids have also been created. These molecules function in the same way as natural nucleic acids, but can perform a similar function. In fact, scientists are using these molecules to build the basis of an ‘artificial life form’, which could maintain the artificial nucleic acid and extract information from it to build new proteins and survive.
Generally speaking, nucleic acids themselves differ in each of the following ways organism depending on the nucleotide sequence within the nucleic acid. This sequence is “read” by the cellular machinery to connect the nucleotides to each other. amino acids in the correct sequence, building complex protein molecules with specific functions.
Nucleic acids and genetics
The genetic code
Today, scientists know that the source code of cells is literally written in nucleic acids. Genetic engineering changes the traits of organisms by adding, deleting or rewriting parts of their DNA and subsequently changing the “parts” that cells produce.
A sufficiently skilled genetic “programmer” can create the instructions for a living cell from scratch using the nucleic acid code. Scientists did exactly that in 2010, using an artificial DNA synthesiser to “write” a genome from scratch using fragments of source code taken from other cells.
All living cells on Earth “read” and “write” their source codes in almost exactly the same “language” using nucleic acids. Sets of three nucleotides, called codons, can code for any given amino acid, or to stop or start protein production.
Other properties of nucleic acids can influence DNA expression in more subtle ways, such as sticking together and making it difficult for DNA enzymes to gain access to DNA. transcription to the code they store.
The fact that all living cells on Earth “speak” nearly the same genetic “language” supports the idea of a universal common ancestor, i.e., the idea that all life on Earth today began with a single primordial cell whose descendants evolved to give rise to all modern living species.
From a chemical perspective, nucleotides that are joined together to create nucleic acids consist of a five-carbon sugar, a phosphate group and a base containing nitrogen. The following image shows structural drawings of the four DNA and the four RNA nitrogenous bases used by living things on Earth in their nucleic acids.
It also shows how the sugar-phosphate “backbones” join at an angle that creates a helix, or a double helix in the case of DNA, when several nucleic acids are joined together into a single molecule:
Nucleic acids are polymers of nucleotides.
DNA and RNA are polymers made of individual nucleotides. The term “polymer” comes from “poly” for “many” and “mer” for parts, referring to the fact that each nucleic acid is made of many nucleotides.
Because nucleic acids can be produced naturally by reacting inorganic ingredients together, and because they are arguably the most essential ingredient for life on Earth, some scientists believe that the first “life” on Earth may have been a self-replicating amino acid sequence. that was created by natural chemical reactions.
Nucleic acids have been found in meteorites from space, demonstrating that these complex molecules can be formed by natural causes even in environments where there is no life.
Some scientists have even suggested that such meteorites may have helped create the first self-replicating nucleic acid “life” on Earth. This seems possible, but there is no firm evidence to say whether it is true.
Nucleic acid structure
Because nucleic acids can form huge polymers that can take many forms, there are several ways to discuss “nucleic acid structure”. It can mean something as simple as the sequence of nucleotides in a piece of DNA; or something as complex as how the DNA molecule folds and how it interacts with other molecules. Nucleic acids are formed mainly from the elements carbon, oxygen, hydrogennitrogen and phosphorus.
Nucleic acid monomer
Nucleotides are the individual monomers of a nucleic acid. These molecules are quite complex and consist of a nitrogenous base plus a “backbone“sugar and phosphate. There are four basic types of nucleotides, adenine (A), guanine (G), cytosine (C) and thymine (T).
When our cells assemble nucleotides to form polymers called nucleic acids, it binds them together by replacing the 3′-oxygen molecule of the 3′-sugar backbone of a nucleotide with the oxygen molecule of the 5′ sugar of another nucleotide.
This is possible because the chemical properties of nucleotides allow the 5′ carbons to bind to multiple phosphates. These phosphates are attractive binding partners for the 3′-oxygen molecule of the 3′-oxygen of the other nucleotide, so that the oxygen molecule opens up to bind with the phosphates and is replaced by the oxygen of the 5′-sugar. The two nucleotide monomers are fully covalently bonded through that oxygen molecule, making them a single molecule.
Nucleotides are the monomers of nucleic acids, but just as nucleic acids can serve other purposes besides carrying information, so can nucleotides.
The vital energy-carrying molecules ATP and GTP are made of nucleotides, the “A” and “G” nucleotides, as you might have guessed.
In addition to carrying energy, GTP also plays a vital role in the G-protein signalling pathways of cells. The term “G-protein” actually comes from the “G” in “GTP”, the same G found in the genetic code.
G-proteins are a special type of protein that can cause signalling cascades with important and complex consequences within a cell. When GTP is phosphorylated, these G-proteins can be turned on or off.