Video Transcript
Keratin is a long protein found in
hair and nails, with many repeats of the sulfur-containing amino acid cysteine. Using the table provided, determine
the group of proteins that keratin is most likely to belong to.
Proteins can be classified into
globular and fibrous, according to their structure, or simple and conjugated,
according to their composition.
Now, we need to use the clues given
in the question to classify keratin. The first clue we are given in the
question is that keratin is a long protein and also that it’s found in hair and
nails, which are strong, stable, and insoluble structures. This suggests that keratin is
classified as a fibrous protein. Let’s see if we can confirm
this.
Next, the question tells us that
keratin contains many repeats of the amino acid cysteine. This also fits with the definition
of a fibrous protein, which is a protein that has a repetitive primary
structure. Each cysteine contains a thiol or
SH group. Thiol groups can form disulfide
bridges with other thiol groups. This plays an important role in the
secondary and tertiary structure of the protein, providing additional stability and
insolubility.
We can now answer our question. Keratin is most likely to belong to
the group of fibrous proteins.