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2nd HIGH SCHOOL BIOLOGY BLOG
DEXOSIRRIBUNU... ACID what?!
Dexosirribonu... acid what?! Don't worry if you don't know what it is, because after reading the post, you will even be able to explain it to your friends.
Nucleic acids are high molecular weight organic macromolecules that are made up of C, H, O, N and P.
We find two types:
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DNA: Deoxyribonucleic acid.
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RNA: Ribonucleic acid. Depending on their location and the function they perform during protein synthesis, it can be: messenger RNA, transfer RNA, ribosomal RNA, nucleolar RNA, small nucleolar RNA, or interfering RNA.
Nucleic acids are made up of nitrogenous bases, a pentose, and a phosphoric acid.
Nucleoside
It is the union of a pentose (ribose or deoxyribose) and a nitrogenous base, which can be pyrimidine if it is guanine or cytosine, or puric if it is adenine, thymine (DNA) or uracil (RNA), through a bond N-glucosidic between the C1 'of the pentose and a nitrogen of the base that will be the N1, if it is pyrimidine, or the N9 if it is puric.
Nucleotide
It is formed by the union of a phosphoric acid molecule with the pentose of a nucleoside through an ester-type bond, which occurs when an -OH of phosphoric acid is esterified with a -OH free of pentose, normally that of C5 ' and in its formation water is released.
In addition, they can be divided into two groups according to whether or not they are part of nucleic acids:
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Nucleic nucleotides bind together and form nucleic acids.
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Non-nucleic nucleotides are not part of nucleic acids, but they are compounds of great interest.
Polynucleotides.
Nucleic acids are polynucleotides, that is, they are made up of many nucleotides that join together in long chains. This union occurs through an ester bond that is formed, between a -OH of the phosphoric acid of one nucleotide that is attached to the C5 'of pentose and the -OH of the C3' of pentose of the next nucleotide, therefore, each phosphoric acid molecule forms 2 ester bonds. This bond is called the 5'-3 'phosphodiester bond.
On the other hand, nucleic acids are divided into 2 groups according to the nucleotides that constitute them:
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Deoxyribonucleic acid or DNA: made up of deoxyribonucleotides.
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Ribonucleic acid or RNA: made up of ribonucleotides.
DNA (DEOXYRIBONUCLEIC ACID)
DNA are macromolecules formed by deoxyribonucleotides-5'-monophosphates of: adenine, guanine, cytosine and thymine that are linked together by 5'-3 'phosphodiester bonds. In most cases it is double-stranded, that is, it is made up of two nucleotide chains, although in some viruses it is single-stranded. In addition, there are different levels of structural complexity that are:
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The primary structure is the nucleotide sequence of a chain or strand.
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The secondary structure: it is the most important and well-known, that is why I will develop it below.
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The tertiary structure is the 20 Å fiber twisted on itself that forms a superhelix. This supercoiling occurs because one of the two chains turns more to the right than the other and, therefore, the tension increases.
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Packaging levels:
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First level packing or 100 Å chromatin fiber or "pearl necklace".
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Second level packing or 300 Å chromatin fiber or "solenoid".
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Third level of packaging or “looping domains”.
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Higher levels of packaging.
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Source: own image.
Source: Pixabay.
Secondary structure of DNA.
The secondary structure is the spatial arrangement of the two polydeoxyribonucleotide chains that make up the DNA molecule.
Based on the discoveries previously made by other scientists, Watson and Crick proposed the double helix model for DNA. According to which:
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The DNA molecule is made up of two antiparallel polydeoxyribonucleotide chains, that is, they are oriented in the opposite direction, one has a 5'-3 'sense and the other 3'-5'.
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Both chains are complementary with respect to their nitrogenous bases that are arranged one in front of the other, by means of hydrogen bonds. The confrontation occurs between complementary bases and between a puric and a pyrimidine A = T and G≡C or vice versa. Therefore, the chains are said to be complementary.
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The winding of the double helix is dextrorotatory (right) and plectonemic, that is, it is wound one over the other and to separate it it is necessary to rotate them with respect to each other.
RNA (RIBONUCLEIC ACID)
RNA is made up of a single nucleotide chain, the primary structure of which is similar to that of DNA, except for the substitution of deoxyribose by ribose and thymine by uracil. On the other hand, there are areas in which the RNA is double-stranded called hairpins or '' horseshoe loops ''. Furthermore, RNA chains are shorter than DNA chains, have a smaller molecular weight, and can be located both in the nucleus and in the cytoplasm. Several types of RNA are differentiated: rRNA, tRNA, mRNA, and RNA.
Messenger ribonucleic acid (mRNA)
The mRNA is formed by a single chain of ribonucleotides, which can have up to 5000. It represents 5% of the total RNA, it is single-stranded and generally linear. Its function is to copy genetic information from DNA (transcription). Once copied, it leaves the nucleus through the pores of the nuclear membrane and carries this information to the ribosomes of the cytoplasm so that proteins are synthesized.
Source: meanings.com
Transferring ribonucleic acid (tRNA)
TRNA is made up of a single strand of ribonucleotides that is bent. In some areas the complementary bases (AU, CG) face each other and are joined by hydrogen bonds, presenting a secondary double helix structure. In these molecules, four areas are differentiated in which the bases face each other and which are called arms. And three other areas called loops or handles with a single-chain structure that are located at the ends of the arms and in which there is no confrontation between the bases. In addition, it is shaped like a clover leaf.
Finally, their function is to capture amino acids in the cytoplasm and transport them to ribosomes, placing them according to the sequence of the mRNA to synthesize proteins.
Source: wikimedia.commons .
Ribosomal ribonucleic acid (rRNA)
Ribosomal RNA is the most abundant of all and represents 80% of the total. It is made up of molecules of different sizes made up of a single ribonucleotide chain and in some areas they present a double helix secondary structure. Also, these associate with a large number of different proteins and form ribosomes. On the other hand, the mass of ribosomes and rRNA is usually expressed in Svedberg (S) units. Prokaryotic cells have 70S ribosomes and eukaryotes 80S.
Nucleolar ribonucleic acid (RNAn)
Nucleolar RNA is the main component of the nucleolus that originates from different segments of DNA. First, a 45 S RNA is formed in the nucleolus that associates with cytoplasmic proteins and forms a ribonucleoprotein. This is divided into three RNAs and associates with another 5S RNA with proteins and that has been synthesized in the nucleoplasm from another DNA fragment. From them, two ribosomal subunits are formed, one of 40 S and the other of 60 S that cross the nuclear membrane and pass to the cytoplasm, where when an mRNA arrives, they associate giving rise to a ribosome.
Source: Santillana slideplayer
FUNCTIONS OF NUCLEIC ACIDS.
As we have seen previously, DNA is the molecule that carries the genetic information that determines the characteristics of the individual. In addition, DNA carries the information that allows the synthesis of all the proteins in the body. This process of protein synthesis is carried out in two stages and RNA also intervenes:
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Transcription: in this stage the information of a DNA fragment, corresponding to a gene, is copied to the mRNA.
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Translation : the nucleotide sequence of the mRNA is translated in ribosomes with the help of tRNAs into a certain amino acid sequence, that is, into a certain protein.
However, nucleic acids also carry out the function of duplication or replication that allows the transmission of this information from one generation to another.
You have finally reached the end of this post, I hope you have learned a lot and as a gift you can see the outline of all the contents of the topic of nucleic acids to settle the information. In addition, I have included a sheet with notes and a summary of the main ideas extracted from a video following the Cornell Method. I highly recommend it because it gives you a global view of the subject and helps you acquire the content more easily.
See you in the next post! :-)
Information obtained from the syllabus and class notes.
The images are their own or from the Wix bank of photographs and gifs.
Source: own image.