Video Transcript
The diagram provided shows the
basic structure of hemoglobin. Hemoglobin is a protein found in
red blood cells. What feature of hemoglobin makes it
suitable for its role in the human body? (A) Hemoglobin forms long, flexible
fibers that increase the elasticity of red blood cells. (B) Hemoglobin has a globular
structure that can bind to oxygen molecules and transport them around the body. (C) Hemoglobin binds to glucose in
the blood and breaks it down to release energy. Or (D) hemoglobin binds to hormones
in the blood that help regulate the water content of the body.
The question asks us about the role
of hemoglobin in the human body and tells us that it is a protein primarily found in
red blood cells. Proteins can be classified into two
major groups, fibrous and globular. Fibrous proteins consist of long,
parallel polypeptide chains. They are insoluble in water and
typically have a very stable structure, making them well suited for their roles of
providing structure and facilitating movement. An example of a fibrous protein is
collagen, which acts like a scaffold to give structure to tendons, ligaments, skin,
muscles, and bones. In fact, collagen is so ubiquitous
that it makes up around one-third of your body’s total protein content.
Globular proteins are irregular in
shape but are roughly spherical. They have a less stable structure
than fibrous proteins and are typically water-soluble. Globular proteins are chemically
active, which facilitates their role of carrying out metabolic functions. Hemoglobin is an example of a
globular protein. It is composed of four folded
polypeptide subunits.
Proteins can also be classified as
simple or conjugated. Conjugated proteins consist of a
protein attached to a nonprotein component, while simple proteins do not have
nonprotein components. For example, hemoglobin is
classified as a globular, conjugated protein because each of its four subunits is
associated with a nonprotein component called a heme group. Each heme group contains an iron
ion, which can bind to and release oxygen, allowing hemoglobin to efficiently carry
and deliver oxygen to all the cells of the body.
Now that we briefly discussed the
structure and function of hemoglobin, let’s revisit our answer choices. Choice (A) describes a fibrous
proteins. And we now know that hemoglobin is
a globular protein, so we can rule this answer choice out. We also know that hemoglobin binds
oxygen, not glucose or hormones. So, we can rule out choices (C) and
(D) as well. Therefore, the feature of
hemoglobin that makes it suitable for its role in the human body is (B). Hemoglobin has a globular structure
that can bind to oxygen molecules and transport them around the body.
