Why does a protein not function after it has been denatured?
a. The R groups form additional bonds causing the structure to become more compact.
b. The normal bonding between the beta sheets has been disturbed and the protein loses its normal shape.
c. The normal peptide bonds are ruptured and the individual amino acids are not held together any more.
d. The normal bonding between the R groups has been disturbed and the protein loses its normal shape.
e. The normal bonding between the hydrogens in the alpha helix has been disturbed and the protein loses its normal shape.

Denaturation is the loss of function of a protein due to its altered three-dimensional structure. To function properly, proteins must be present in a properly folded form. The three-dimensional structure and protein folding are mediated by weak interactions such as hydrogen bonds, electrostatic interactions, etc. An abrupt increase in temperature, pH or presence of some organic solvents causes protein denaturation.

The organic solvents target the hydrophobic interactions between the R groups of amino acids that make the core of globular protein stable. Extreme levels of pH target the net charge on proteins and thereby results in electrostatic repulsion between closely placed amino acids. Extremes of pH also disrupt the hydrogen bonding between the R groups of the amino acids. The effect is the loss of the three-dimensional structure of proteins, their partial or complete unfolding and loss of function.