The right answer is proteins.
Protein functions are very varied and are used as a basis for classification.
There are several groups:
* Enzymatic proteins: any protein catalyzing biological reactions Antibodies: defense proteins
* Transport proteins (molecules, or various ions): we can mention myoglobin and hemoglobin, which are capable of binding reversibly oxygen, but also blood lipid transporters, membrane transporters ( pump type, channels ...)
* Regulatory proteins: they participate in the regulation of extremely diverse cellular or physiological processes. We can mention: protein hormones, all the receptors and proteins associated with these receptors, the proteins involved in cellular transduction phenomena, all the proteins involved in the control of gene expression ...
* Contractile proteins: involved in cell motions. We can mention: actin, myosin, tubulin
* Reserve proteins: serve as reserve amino acids, stored massively at a period of development then are used and hydrolyzed massively at another stage of development: ovalbumin of eggs, grains of aleurones in the albumen seeds (which contain gluten in wheat ...)
* Architectural proteins, which participate in the construction and maintenance of cell and tissue structures, but also participate in the protection of certain types of cells: keratin, collagen, fibroin (spider webs) ...
