Video Transcript
Prions are misfolded proteins that
are considered infectious agents. They can infect humans and cause
normal protein variants to misfold, leading to serious diseases, including
neurodegenerative disorders. Which of the following is correct
about classifying prions? (A) Prions are part of humans and
other mammals, so they can be classified into kingdom Animalia. (B) Prions are considered
nonliving, so they cannot be classified into any of Whittaker’s five kingdoms. (C) Prions do not contain cellular
organelles, so they can be classified into kingdom Monera. (D) Prions have infectious
qualities, so they can be classified into kingdom Monera.
This question is asking us about
the classification of prions. Are they considered living? What biological classification do
they fall under? Let’s first describe what a prion
is.
Prions are misfolded proteins that
have the ability to cause serious disease in humans and animals by affecting the
folding of healthy proteins. Notice how the original prion
associated with a normal protein to form a new prion. This process can continue where
normal proteins are converted into prions, forming clumps of misfolded proteins. This can lead to accumulations in
the brain and neurodegenerative disorders, which can ultimately lead to death.
Since this question is asking us
about classifying prions, let’s take a look at Whittaker’s five-kingdom
classification system. This includes Protista, consisting
of eukaryotic, unicellular organisms or simple cellular colonies; Monera, consisting
of all prokaryotic organisms; Fungi; Plantae; and Animalia. The kingdom Monera includes all of
prokaryotic life, which are characterized by the absence of membrane-bound
organelles.
Like prokaryotes, prions don’t
contain membrane-bound organelles. But prions are not prokaryotes
because they are not cellular. So, they cannot be classified as
part of this kingdom. So, answer choices (C) and (D) are
incorrect.
Even though prions may infect
humans, they themselves can’t be classified as animals. Prions are not eukaryotic or
multicellular because they have no cellular structure. Therefore, answer choice (A) is
incorrect.
Prions have the ability to cause
properly folded proteins to misfold, thus replicating themselves. But despite being able to
replicate, which is a characteristic of living organisms, they are considered
nonliving. Whittaker’s five kingdoms only
encompass life, and thus prions cannot be classified into any of these kingdoms. So, the correct option for
classifying prions is given by answer choice (B). Prions are considered nonliving, so
they cannot be classified into any of Whittaker’s five kingdoms.
