Unit 4 - Prions and Viroids/Disease

Unit 4, Chapter 17 and Chapter 18

Prions

a type of protein that have no genetic material and are very similar to viruses.

How do prions survive?

They must thrive off of a host ike viruses, but they do not directly infect organisms.

What to prions do to find a host?

prions attach themselves to organisms that they cannot infect, like plants, and then the plant that the prion attaches to gets eaten by other organisms that the prions can then further infect.

the only organisms that are known to be susceptible to prion infection

animals

How do prions cause damage?

They interrupt how a host’s proteins function by changing the protein’s shape.

How can a protein properly function?

only when it is in the correct shape.

How do prions change proteins?

when a prion is near a protein, it can unfold and refold that protein.

What occurs during the refolding of proteins by prions?

the protein folds into the same shape as the prion, therefore creating a new type of prion.

How does refolding process damage the cell?

it stops normal proteins from functioning properly, which is also the way the prion reproduces (through refolding)

Viroids

the smallest known pathogens and do not have a protein coat.

Opposite behaviors from viroids compared to prions:

viroids are made up of a single RNA molecule, no proteins and they solely infect plants

How do viroids reproduce?

They use RNA Polymerase (used in viruses) which is responsible for making new RNA and exists within all host cells. The viroid RNA strand tricks the host’s RNA polymerase into believing that it is a DNA strand.

What happens after the RNA polymerase is deceived by the viroid?

The RNA Polymerase copies the viroid RNA strands.

How does the reproduction process of viroids differ from RNA-based viruses?

They differ because the RNA-based virus uses RNA Polymerase to turn RNA into DNA.

Pathogens

infectious organisms that can cause disease

Disease

conditions within an organism that prevent it from functioning normally

What do all living things have in relevance to pathogens?

All organisms have a reaction to being infected by pathogens

Immune System

the human’s defense mechanism against pathogens, responsible for protecting the body from foreign substance and diseases

Pathologists

a scientist who studies disease and their causes