Final answer:
Soluble proteins typically have polar and charged amino acids on their surface and non-polar amino acids on their interior. In contrast, proteins in a lipid bilayer have non-polar and uncharged amino acids on the surfaces that interact with the membrane.
Step-by-step explanation:
On the surface of a soluble protein, you would typically find polar and charged amino acids. This is because these amino acids are hydrophilic (water-loving) and interact favorably with the aqueous environment in which soluble proteins are found. On the other hand, non-polar amino acids, which are hydrophobic (water-fearing), are generally located in the interior of the protein, where they are shielded from water. Examples of polar amino acids you might find on the surface of a protein include serine, threonine, and cysteine. Non-polar amino acids such as valine, methionine, and alanine are often found in the interior.
In proteins embedded in a lipid bilayer, like those in the plasma cell membrane, you would expect to find non-polar and uncharged amino acids on the surface that interact with the hydrophobic core of the membrane. The distribution of amino acids in these transmembrane proteins facilitates their integration into the lipid bilayer and their proper function.