T cells initiate the adaptive immune response by interacting MHC on antigen-presenting cells that have been exposed to pathogens. 

TLS Online TPP Program

#Id: 8279

#Unit 1. Molecules and their Interaction Relevant to Biology

Charge–charge (ionic) interactions

These interactions occur between the side chains of oppositely charged residues as well as between the NH3+ and COO− groups at the ends of polypeptide.

TLS Online TPP Program

#Id: 8280

#Unit 1. Molecules and their Interaction Relevant to Biology

Coulomb’s law describes the potential energy (V) between two separated charges (in a perfect vacuum) according to the relationship.

TLS Online TPP Program

#Id: 8281

#Unit 1. Molecules and their Interaction Relevant to Biology

In absence of water the magnitude of the charge–charge interaction is significantly greater.

TLS Online TPP Program

#Id: 8282

#Unit 1. Molecules and their Interaction Relevant to Biology

Hydrophobic interaction describes the influences that cause nonpolar substances to cluster together to minimize their contacts with water.

TLS Online TPP Program

#Id: 8283

#Unit 1. Molecules and their Interaction Relevant to Biology

The dissolution of nonpolar molecules in water is unfavourable because of the large decrease in entropy resulting from clathrate formation, even though the process is exothermic (dH < 0) But unfavourable dG > 0.

  

TLS Online TPP Program

#Id: 8284

#Unit 1. Molecules and their Interaction Relevant to Biology

During hydrophobic interaction, the non-polar molecules come together, releasing some of the ordered water molecules in the clathrate structure and thus increasing entropy.

This is a thermodynamically favourable process (dG < 0), even though it is endothermic (dH > 0) because more hydrogen bonds are broken than are made.