Protein
From CreationWiki, the encyclopedia of creation science
Proteins are molecular machines that perform the majority of the biochemical processes within cells. They also serve as the building blocks for many structural components. Their ubiquitous use as builders and building materials alike makes it easy to see why proteins are indeed the material that makes life happen.
Proteins are assembled in a complex series of biochemical reactions known as gene expression. Genes are basically the instructions or blueprints that tell the cell how to make proteins, and the information contained within many gene is usually required to produce a single functional protein.
Proteins are composed of amino acids that are linked together by peptide bonding. Amino acids have many structures, but the basic formula is NH2-C-COOH. Each contains an amine group (NH2) and a carboxylic acid (COOH), thus their name - amino acid. Amino Acids are first linked together to form long chains called polypeptides, which after further modification are called proteins.
Proteins are composed of twenty different types of amino acids. Most proteins form globular structure and others are chain-like. Proteins have 2 distinctive types of functions: structural and biological activity. However, some proteins serve both functions. Important structural proteins in animals include collagen, which is the component of the bones, muscles and skin, and keratin, which is the component of the hair, feather, and finger nails.
Contents |
History
Jons Jakob Berzelius discovered Protein in 1938. He named Protein from the Greek word protas, which means the hightest importance. [1]
Synthesis
- Main article:Translation
Protein synthesis is the result of a complex cellular process known as gene expression. The process begin when the gene is activated to transcribe a single stranded copy of itself known as messenger RNA (mRNA). The mRNA from the gene is transported to an organelle in the cytoplasm called a ribosome where it is translated into a chain of amino acids (polypeptide). Every 3 nucleotides along the length of the gene represents a coding unit called a codon. These codons specify the amino acid that is to be inserted into the growing peptide chain. Another RNA molecular called a transfer RNA (tRNA) brings amino acids to the ribosome. The codon of the tRNA is compared with that on the mRNA, and if they are complementary, the amino acid is incorporated into the growing protein chain.
| Examples of nucleotide codons and their corresponding amino acid: Codon - Amino Acid TGC = Cysteine CTG = Leucine AGT = Serine GCA = Alanine |
In the protein synthesis, there are two parts of the process: transcription and translation.
After corresponding DNA molecules produce RNA by the transcription, the genetic information needs translation of the corresponding of RNA the coressponding of amino acids. In the eukaryotic cells DNA's transcription happens in the nucleus, and translation happens in the cytoplasm. Transcription forms mRNA to release it from the nucleus, mRNA is translated in the ribosomes. tRNA needs active amino acids groups, and it carries amino acids to the ribosome. This way protein's polypeptide chain is connected continuously.
Structure
The product of a single gene is a string of amino acids known as a peptide or polypeptide. This is known as the primary structure of a protein. This peptide is folded into a particular subunit, and then joined together with other peptides to make a functional protein. The structure of protiens have the order: primary, secondary, teriary, and quartenary protein structures. (They are occurring by the order.) [2]
Primary
The first structure of protein is primary protein structure or primary protein stage. The primary structure consists the repeating sequence of three atoms: N-C-C. N is alpha helix, and C is carboxyl group. The structure of proteins is bonded by the covalent bonds. From the primary stage, the translation is occurring; the amino acis form to bond into the special order of them. (Polypeptide, group of amino aicds, is the sequence of amino acids in the primary stage.) The seqence of amino acids determines how to protein to twist or form. Proteins can be distincted by the stable structures. [3]
 |  |
Secondary
Secondary structure is occurring after the priamry structure. It consists the regular repeating patterns in the polypetide chains. Hydrogen bonding plays an important role in stabilizing these folding patterns. In the secondary structures, there are two different types of the structures: alpha helix and beta pleated sheet. Each of the structures work differently, even though they are occurring in the secondary structure. [4]
- Alpha helice: Alpha is a right handed coil. The alpha helical secondary structure is common in keratins, which is the fibrous structural protein: hair, feather, and toe nails.
- Beta pleated sheet: Beta pleated sheet is formed from two or more polypeptide chains. It is stablized by the hydrogen bonds between N-H and C-O groups.
Tertiary
Of course, tertiary structure occurs after the secondary structure. The tertiary structure is the polypeptide and proteins are composing it as the secondary structure of protein. Polypetides in tertiary structure can be bent and be folded back and forth. Many of the interactions between atoms are occurred in tertiary structure.[5]
- Covalent disulfide bridges: They can hold the folded polypetides
- Hydrophobic: Side chains are gathered together in protein to fold the polypeptides that the process occurs away from water
- Van der Waals force: It stablize the interations bewteen the hydrophobic residues.
- Ionic bonds: They form between positive and negative charges.
Quartenary
The quartenary structure describes the interaction of proteinaceous subunits with other subunits or different molecules. The quaternary stricture is specifically the result of binding of the subunits together and their interactions. The protein subunits are the short tertiary polypeptide chains. The tetrameric metalloprotein hemoglobin is a good illustration of the quartenary structure. Hydrogen bonds, ionic bonds, Van der Waals forces, and hydrophobic bonds hold four different subunits together (2 α subunits and 2β subunits) along with an Fe(II) ion. The presence of the iron allows oxygen binding and transportation in the form of oxyhemoglobin during cellular respiration. When oxyhemoglobin releases O2 in the cells of the body, the quaternary structure undegoes a change. [6]
References
- Protein Structure Advancing the Chemical Science
- Some Protein History Associated Content
- Protein & Polypeptide Structure About Chemistry
See Also
 Browse |
Categories: Biology | Cell biology | Genetics | Chemistry | Biochemistry | Compound | Protein
