Proteins
Proteins play a major role in maintaining the healthy function of an organism. There are proteins specialized for speeding up reactions, transporting substances, maintaining structure, etc. Examples of proteins include enzymes, hemoglobin, insulin, and antibodies.
The monomers for proteins are called amino acids, and the polymers are called polypeptides. Amino acids can be joined by dehydration and broken down by hydrolysis. There are twenty common amino acids and a few rare ones.
The monomers for proteins are called amino acids, and the polymers are called polypeptides. Amino acids can be joined by dehydration and broken down by hydrolysis. There are twenty common amino acids and a few rare ones.
Primary StructureThe primary structure of a protein is simply a chain of amino acids joined together. It has no biological functions at this stage. Peptide bonds are responsible for the primary structure.
Secondary StructureIn the secondary structure of a protein, the polypeptide chain twirls into an alpha helix or folds into a beta pleated sheet. The shape of the secondary structure is maintained by hydrogen bonds between polar hydrogen and oxygen atoms on the helix or pleated sheet.
Tertiary StructureIn this level of protein structure, the polypeptide forms a unique three-dimensional shape stabilized by interactions between the R groups (side chains). The hydrophobic side chains will group together in the interior of the protein, away from water. Van der Waals interactions holds them together. The polar side chains form hydrogen bonds with each other. The electrically charged side chains will form ionic bonds. Disulfide bridges are also formed between cysteine amino acids, the adjacent sulphur atoms bond to bring parts of the protein together.
Quaternary StructureSome proteins require more than one polypeptide chain in their functional form, this is called the quaterary structure. In order to achieve this level of organization, multiple tertiary protein structures become aggregated together to form a macromolecule. Examples of proteins that have a quatnerary structure are hemoglobin (found in blood) and collagen (structural protein).
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Protein SynthesisThe information for protein production is stored in the cell's DNA. When a protein is to be made, the DNA sends messenger RNA to activate a ribosome in the cytoplasm. The messenger RNA has specific instructions on what protein to make. The ribosome follows these instructions and produces a polypeptide.
Recently researchers have discovered the use of chaperonins in the process of protein folding. A chaperonin works by protecting the polypeptide chain from external influences which could affect its proper folding. A polypeptide chain would enter a chaperonin and come out as a correctly formed protein. DenaturationProteins are vulnerable to changes in their environment. For example, if a protein is in a solution with a really high temperature, the protein may unfold itself. Now the protein can no longer function properly. Similarly, a protein can become denatured if the pH becomes too acidic or too basic, if the salt concentration is too extreme, or if there are chemicals that disrupt the normal interactions between the side chains.
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