Video Transcript
Which of the following is an example of a structural protein? (A) Adrenaline, (B) testosterone, (C) cytokines, (D) keratin, or (E) amylase.
One way to characterize different types of proteins is based on their function as
either a structural protein or a regulatory protein. Regulatory proteins are proteins that regulate different processes and activities
within the organism. They have specific 3D shapes that often need to be compatible with other molecules or
proteins to perform their functions and may not have repeating units like structural
proteins. There are several categories of regulatory proteins. Enzymes, like peptidase or amylase, can help speed up chemical reactions. We can therefore eliminate option (E) as amylase is not an example of a structural
protein.
Antibodies and cytokines are regulatory proteins that play an important role in the
immune system. We can also eliminate answer choice (C), as cytokines are not structural
proteins.
Hormones are regulatory proteins that act as chemical messengers. They affect gene expression and influence function in their target cells. Some examples of hormones include insulin, glucagon, adrenaline, and
testosterone. We can also eliminate options (A) and (B), as these hormones are examples of
regulatory proteins.
Structural proteins on the other hand are the building materials of the body. They often have repeating units and shapes that give them their mechanical strength
to provide structure to cells. The 3D shape of these proteins makes them ideal for forming fibers that can give
cells stability. Examples of structural proteins include actin and myosin, which are important
components of muscle cells. Keratin is another example of a structural protein. Keratin actually describes a group of proteins that are critical components of the
cell’s cytoskeleton.
Here you can see two helices that are formed from two separate keratin proteins. These individual keratin helices can then associate with each other to form dimers,
which are complexes formed by the association of two proteins. These dimers can then associate with other keratin dimers to form filaments. And those filaments give hair, skin, and nails their mechanical strength and
structure. So, to answer the question, an example of a structural protein is keratin.
