Catabolic vs. Anabolic reactions
Catabolic: (Destructive metabolism; breaks down complex substances into simpler ones; produces energy)
Anabolic: (Creates more complex molecules from simple molecules and consumes energy)
Both: Metabolic processes
Virus: An agent that infects a cell with its DNA and uses it as its host to multiply. It's microscopic and it causes deadly diseases that cannot be killed with antibiotics.
ex: Aids
Viroid: Single stranded RNA molecules that are usually plant pathogens, however they can be human pathogens as well. Unlike viruses, they lack a protective protein coat.
ex: Hepatitis D
Prion: Nerve protein fibers in cow brains that lack methionine and cysteine.
ex: mad cow disease
Are prions, viruses, and viroids living?
The only characteristic they share with living things is the ability to reproduce. For example, virus are only able to reproduce by attaching themselves to living things, such as cells. All of these are in the border zone of living and non-living since they have living and non-living characteristics. I personally think that they are all non-living, since they can only reproduce through living things.
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