Protein Structure Flashcards
What is the primary structure
The sequence of amino acids in a protein
List of sequence of amino acids in the polypeptide
What is the secondary structure
The shape of local regions of a polypeptide, resulting from the interaction of amino acids.
The secondary structure of a protein describes the 3D form of local segments of a polypeptide chain held with weak hydrogen bonds
eg; twists and turns inside the protein
What is the tertiary structure
The tertiary structure of a protein is the 3D functional shape of the protein
The tertiary structure is the most important level of structure. This is because the shape of a protein, to a very large extent, determines the function of the protein.
The tertiary structure of a protein forms through polypeptides being folded into their 3D shape by other proteins in the cell called chaperone proteins.
Once they are folded, they are held in position by weak hydrogen bonds and disulfide bonds between cysteine amino acids.
Quaternary structure
If a protein has a quaternary structure, it is made of more than a single polypeptide chain, each with their own primary, secondary and tertiary structure. The polypeptides are held together by weak hydrogen bonds and the attraction between polar amino acid side chains.
What is an alpha helix
Alpha helix:
An alpha helix is a common feature in polypeptide bonds.
Forms when a long chain of amino acids have factors in their side chains that make them push away from other amino acids.
Example; if all side chains are positively charged they will push away from each other.
Amino acids pushing away from each other cause right-hand spiralling of the polypeptide, forming the Alpha helix.
Alpha helix are held together through weak hydrogen bonds which form between the hydrogen in each amine group and the oxygen in the carboxyl group four amino acids further up the chain.
