Answer: Aminoacids
Explanation:
Proteins are macromolecules formed by linear chains of amino acids. They are assembled in various ways, allowing them to participate as the main structural components of cells and tissues. For this reason the growth, repair and maintenance of the organism depend on them. Some of their functions are:
- Structural: this is the most important function of a protein (e.g. collagen)
- Protective or defensive (thrombin and fibrinogen)
- Enzymatic (sucrose and pepsin)
- Immunological (antibodies)
- Crust production (e.g. fibrin)
- Homeostatic: they help to maintain the pH (as they act as a chemical buffer)
- Contractile (actin and myosin)
<u>Proteins are assembled from their amino acids using the information encoded in the genes. Each protein has its own amino acid sequence that is specified by the nucleotide sequence of the gene that encodes it. </u>
The genetic code is made up of a set of tri-nucleotides called codons. Each codon (combination of three nucleotides) designates an amino acid. Since DNA contains four different nucleotides, the total number of possible codons is 64; therefore, there is some redundancy in the genetic code, with some amino acids being encoded by more than one codon.
Genes encoded in DNA are first transcribed into pre-messenger RNA by proteins such as RNA polymerase. Most organisms then process this pre-mRNA (also known as primary transcript) using various forms of post-transcriptional modification to form mature mRNA, which is used as a template for protein synthesis in the ribosome.
The process of synthesizing a protein from an mRNA mold is called translation. The mRNA is loaded into the ribosome and read, three nucleotides at a time, matching each codon with its complementary anticodon located on a transfer RNA molecule carrying the amino acid corresponding to the codon it recognizes. The enzyme aminoacyl tRNA synthetase "charges" the transfer RNA (tRNA) molecules with the correct amino acids. The growing polypeptide is called a nascent chain. These proteins are always biosynthesized from the N-terminal to the C-terminal end.
These amino acids are linked together by peptide bonds. Hundreds and thousands of amino acids can participate in the formation of the large polymeric molecule of a protein.
