Question Video: Determining Why Prions Cannot Be Classified into the Five Kingdoms | Nagwa Question Video: Determining Why Prions Cannot Be Classified into the Five Kingdoms | Nagwa

Question Video: Determining Why Prions Cannot Be Classified into the Five Kingdoms Biology • First Year of Secondary School

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 5 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.

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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.

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