Final answer:
The b-pleated sheet conformation is energetically favorable for membrane proteins due to the stability from hydrogen bonds and distinct hydrophobic and hydrophilic surfaces for interaction with the cellular membrane.
Step-by-step explanation:
A b-pleated sheet is an energetically favorable conformation for an integral membrane protein for several reasons. Firstly, the nature of the b-pleated sheet allows for extensive hydrogen bonding between the amide hydrogens and carbonyl oxygens of the polypeptide backbone. This provides stability and strength to the protein structure. The b-pleated sheet includes two or more segments of polypeptide chains aligning side by side, which can run either parallel or antiparallel, further stabilized by these interchain hydrogen bonds.
Moreover, b-pleated sheets have distinct hydrophobic and hydrophilic sides due to their ionic self-complementary characteristics. This is crucial for membrane proteins, which need to interact with the hydrophobic membrane interior and the hydrophilic exterior environment, making the b-pleated sheet structure ideal for membrane integration. The hydrophobic side typically resides within the membrane, while the hydrophilic side interacts with the aqueous surroundings, therefore contributing to the protein's proper placement and function within the lipid bilayer of the membrane.
In summary, the structural organization of b-pleated sheets with their hydrogen bonds and the presence of distinct hydrophobic and hydrophilic faces serve to stabilize the protein within the challenging environment of the cell membrane and contribute to its energetic favorability.