In the case part-way between these two extremes, some peripheral membrane proteins have a patch of hydrophobic amino acids on their surface that locks onto the membrane.
In contrast to integral membrane proteins, peripheral membrane proteins tend to collect in the water-soluble component, or fraction, of all the proteins extracted during a protein purification procedure.
The site of photosynthesis is the thylakoid membrane, which contains integral and peripheral membrane protein complexes, including the pigments that absorb light energy, which form the photosystems.
Some polypeptide hormones, antimicrobial peptides, and neurotoxins accumulate at the membrane surface prior to locating and interacting with their cell surface receptor targets, which may themselves be peripheral membrane proteins.