levels of protein structure Flashcards
Polypeptides
when more amino acids are added to a dipeptide
one or more polypeptide chains folded into a highly specific 3D shape.
four levels of structure
primary, secondary, tertiary and
quaternary.
Primary structure of proteins
sequence of the amino acids in a polypeptide chain
Different proteins have different sequences of amino acids in their primary structure.
Tertiary structure of proteins
coiling or folding of sections of proteins into their secondary structure brings the R-groups of different amino acids into close contact so that they can interact and cause further folding
Ionic bonds: attractions between negatively-charged R groups and positively-charged R groups on different parts of the molecule.
Disulfide bonds: two cysteine amino acids that bond between two sulfur atoms
Hydrophobic and hydrophilic interactions: hydrophobic regions clump together, pushing hydrophilic regions to the outside
Hydrogen bonds: weak bonds between slightly positively-charged hydrogens on some R groups and slightly negatively-charged R groups
Secondary structure of proteins
chain of amino acid twisted into secondary structures
Hydrogen bonds form between the –NH and –CO groups of the amino acids chain to be
pulled into a coil shape called an alpha helix
beta pleated sheets, fold very slightly in a zig-zag
Hydrogen bonds between the –NH group of one amino acid and the –CO group of another strand hold the sheet together.
alpha helices and beta pleated sheets can exist in a single polypeptide.
Quaternary structure of proteins
Several different polypeptide chains come together to form a quaternary structure.
Breakdown of peptides
Proteases are enzymes that catalyse the hydrolysis reaction which turns peptides into their constituent amino acids
A water molecule is used to break the peptide bond reforming the amino group and carboxyl group
