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CIE AS Biology (9700) 2019-2021 Resources

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Page 47

2.3.2 THE FOUR LEVELS OF PROTEIN STRUCTURES

Proteins: Structures

There are four levels of structure in proteins, three are related to a single polypeptide chain

and the fourth level relates to a protein that has two or more polypeptide chains

Polypeptide or protein molecules can have anywhere from 3 amino acids (Glutathione) to

more than 34,000 amino acids (Titan) bonded together in chains

Primary

The sequence of amino acids bonded by covalent peptide bonds is the primary structure of

a protein

DNA of a cell determines the primary structure of a protein by instructing the cell to add

certain amino acids in specific quantities in a certain sequence. This affects the shape and

therefore the function of the protein

The primary structure is specific for each protein (one alteration in the sequence of amino

acids can affect the function of the protein)

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