Question

Proteins can go from a disordered state, typically referred to as a
random coil, to a highly ordered (folded) state. For many proteins, this process
occurs spontaneously under biological conditions (i.e. inside cells). In fact, one
common folding model is the “folding funnel” which describes how configurational
entropy decreases from a large number of microstates in the disordered state to a
small number in the folded state.
Describe how these processes can occur spontaneously without requiring an
external energy source even though the entropy of the protein decreases?

Answer 1

Despite of the fact that protein folding is accompanied by decrease in entropy but still it is a spontaneous process. The Amino acids of proteins are joined by covalent bonding interactions. The polypeptide is folded into a 3 D structure by non bonding interactions. These interactions are:-

Electrostatic Interactions

Hydrogen bond interactions

Vander waal interactions

Hydrophobic interactions

Due to these interactions protein folding is an exothermic process therefore ∆H<0

∆G=∆H-T∆S

∆H<0, ∆S>0

But the value of ∆H is highly negative therefore overoll value of Gibbs free energy is negative.

Therefore Protein folding is a spontaneous process.