DNA, RNA, ATP
DNA
What is DNA ?
Deoxyribonucleic acid is a molecule composed of two polynucleotide chains that coil around each other to form a double helix carrying genetic instructions for the development, functioning, growth and reproduction of all known organisms and many viruses.
Structure
DNA is one type of nucleic acid, and it is composed of monomers called nucleotides, each of which consists of a pentose sugar, a phosphate group and a nitrogenous base-either a pyrimidine or purine. Purines have two fused rings, and the smaller pyrimidines have single ring. Molecules consisting of a pentose sugar and a nitrogenous base, but no phosphate group are called nucleosides.
The nitrogenous bases of DNA are adenine (A), guanine (G), cytosine (C), and thymine (T). Adenine and thymine bond together with 2 hydrogen bonds. Guanine and cytosine bond together with 3 hydrogen bonds.
DNA has an ability to replicate itself. In a cell, it is mainly found in nucleus, mitochondria and chloroplast of eukaryotic cells. In prokaryotes, it is found in the cytoplasm. The genetic code found in DNA is transferred from cell to cell in this way.
RNA
What is RNA ?
Ribonucleic acid is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and DNA are nucleic acids. Along with lipids, proteins, and carbohydrates, nucleic acids constitute one of the four major macromolecules essential for all known forms of life.
Structure
RNA consists of one polynucleotide chain. RNA are also made up of four different monomers, but their nucleotides differ from those of DNA. In RNA, nucleotides are named ribonucleotides, wheres in DNA, deoxyribonucleotides. RNA contain ribose rather than deoxyribose, and instead of base thymine, RNA uses the base uracil (U). The other three bases are the same as in DNA.
There are three types of RNA
mRNA (messenger RNA) carries messages coded in DNA, from nucleus or nucleoid region to the site of protein synthesis that is ribosomes, in cytoplasm. It carried a three nucleotide sequence called codon which is unique for a specific amino acid. %5 of total RNA is mRNA.
tRNA (transfer RNA) transfers the amino acids from cytoplasm to the ribosomes according to the codes in mRNA. It carries a three nucleotide sequence called anticodon which is unique to a specific amino acid. %15 of total RNA is tRNA.
rRNA (ribosomal RNA) is found in the structure of ribosomes together with ribosomal proteins. It is the most abundant RNA, %80 of total RNA is rRNA.
ATP
What is ATP ?
ATP stands for adenosine-tri-phosphate. Adenosine-tri-phosphate is an organic compound and hydrotrope that provides energy to drive many processes in living cells, such as muscle contraction, nerve impulse propagation, condensate dissolution, and chemical synthesis.
Structure
It has adenine nucleotide, ribose sugar and three phosphate groups in its structure. ATP is made of C, H, O, N and P atoms. It is similar to nucleic acids, especially adenine ribonucleotide. All living cells use ATP for energy requiring processes. Energy is stored in high energy phosphate bonds.
ATP cannot be stored in cells, it is built up and broken down continuously. ATP is synthesized during respiration via aerobic or anaerobic respiration. The hydrolysis of ATP that means the breakdown of high energy phosphate bond yields ADP (adenosine-di-phosphate) and energy. ADP can be further broken down into AMP (adenosine-mono-phosphate) with energy.
The dehydration synthesis of ATP or ADP is called phosphorylation, as there is an addition of phosphate group. The hydrolysis of ATP or ADP is also called dephosphorylation, as there is removal of phosphate group.
ATP Cycle
ATP is used for endergonic (anabolic) reactions such as synthesis reactions, active transport across the cell membrane, movements and contraction of muscles, nerve impulse transmission... etc. ATP is produced from exergonic (catabolic) reactions such as aerobic and anaerobic respiration. Therefore, ATP is used and produced in a cell as a cycle.