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| Proteins are a very important part of the human body. The word protein comes from the Greek word proteios, meaning "first place". They make up over 50% of the dry weight of cells and are used for structural support, storage, transport of other materials, signaling from one part of the organism to another, movement, and defense. Proteins can also act as enzymes. All proteins are polymers with the same set of amino acids. Proteins are globular shaped and have four basic levels of structure: primary, secondary, tertiary, and quaternary. |
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| The tertiary structure of a protein is more folding due to bonding of the "R" groups. Hydrogen bonds, hydrophobic interactions, disulfide bridges, and ionic bonds are all examples of bonds contributing to the tertiary structure of a protein. |
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| The secondary structure of a protein includes coiled and folded patterns in the polypeptide chain. This configuration results from hydrogen bonds along the polypeptide backbone. There are two types of secondary structure: the alpha helix and the beta pleated sheet. The alpha helix is a coil held together by hydrogen bonding every fourth peptide bond. The beta pleated sheet is where two regions of the sheet lie parallel to each other via hydrogen bonds. |
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| The quaternary structure of a protein results from the relationship between different sets of individual polypeptide chains called subunits. These chains come together to make a functional macromolecule - a protein. |
| PrPc and PrPsc PrPc is a prion protein that assists with the nervous system. PrPsc is the mutated and infectious form of PrPc. PrPc is naturally a soluble, alpha-helix rich prion protein. When it changes into the insoluble PrPsc form, all but two alpha helixes are changed into beta pleated sheets. The PrPsc form is the prion protein form that is thought to be infectious, and thus associated with prion diseases. |
| PrPc (normal) |
| PrPsc (mutated) |
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| Breanna Ondich - original artwork |
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| Example of a polypeptide chain showing three amino acids with different R groups |
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| PRIMARY STRUCTURE |
| TERTIARY STRUCTURE |
| QUATERNARY STRUCTURE |
| SECONDARY STRUCTURE |
| The primary structure of a protein is its sequence of amino acids, called a polypeptide chain. Most amino acids have a carbon called the alpha carbon, which is bonded to four different covalent partners. Three of them, a hydrogen atom, a carboxyl group, and an amino group, are the same for every amino acid and make up the backbone. The fourth group, often termed the "R group", can be one of 20 different kinds. |
| Breanna Ondich - original artwork |
| Breanna Ondich - original artwork |
| Breanna Ondich - original artwork |