Turnover of Biological Macromolecules Flashcards
What happens to a cell if it is too packed
It will lyse
What is an important molecule that have to be degraded in the cell and there are various redundant mechanism for that
RNA, degraded by RANses.
What are RNAses? What are their types?
They are in the family of hydrolases, they require a metallic cofactor and they have 2 types:
- Exonucleases
- Endonucleases
What are exosomes
They are a ring like structure associated with degrading mRNA and either degrading or maturing rRNA and tRNA
What kind of activity they have
They are phosphorylytic enzyme, substitute a PO4 group instead of water to cleave something, they have both endonucleases and exonucleases activity
What kind of malformation can there be that may stall protein synthesis in the translation process
There can be malformations like RNA hair pin structures can form
What happens when the ribosomes encounter these malformation
Protein synthesis stops
How does a cell deal with these malformation
An endonuclease enzyme is recruited that cuts the mRNA from the middle. Then XRNA1 comes in to chew the mRNA from the 5’ end and exosome chews it from the 3’ end.
What is this process called
No go RNA decay (NGD)
Explain NGD, NMD and NSD
In nonsense mediated decay, the cell identifies the stop codon being placed too early, comes in. Endonuclease comes in to cut the mRNA in half, XRNA1 eats from the 5’ end and exosome eats from the 3’ end.
In nonstop decay, the polyA chain is tackled by the ribsomoes which shouldnt be exposed to them, the cell identifies this as having no stop codon, and the cell recruits exosome to chew this up
Explain the role regulatory RNA in the cell. Where are they placed inside the cell after becoming inactive or nonfunctional.
There are 2 types of regulatory RNAs:
miRNA and siRNAs.
They combine with normal RNA, making them inactive by dimerizing with them, these are then placed in P bodies which are structures without a cell membrane (theyre not sturcture but just a place in the cytosol)
How are these regulatory structures degraded
By exo and endonucleases.
Natural RNA have lower affinity for these enzyme, they have to be decapped, their poly A tail have to be removed and then they are chewed up
When does a cell needs to change its proteins?
When the cell changes cycle
Which proteins are degraded by a protesome and which ones are degraded by lysosomes
The one with short half lives are degraded by proteosomes, the one with longer are degraded by lysosomes
How does a lysosome digest proteins
There are 2 processes involved with this, the first one being autophagy which is the lysosome eats whatever comes in its way, the second one invplved chaperone mediated autophagy which is every selective
