7. a) How are second messengers generated from phosphatidylinositol (Pl)?
b) What are the main function(s) of the second messengers derived from Pl?
9. a) In the context of tumourigenesis, what is a gain-of-funtion mutation?
b) List two effects that gain-of-function mutations may have on encoded protein.
c) Briefly explain two different mechanisms that may lead to gain of function mutations in tumour cells, and give one example of each.
11. a) Explain what is meant by the term 'extracellular matrix' and five two example of proteins that may be found in the extracellular matrix.
b) Name and describe the processes by which tumour cells:
i. move from their site of origin
ii. spread within the body
c) Give two examples of how changes in protein expression by the tumour cells can affect their ability to spread within the body.
12. a) What are free radicals? Give one example of a free radical and briefly outline the process by which it is produced.
b) What particular characteristics of mitochondrial DNA make it more susceptible to damage than nuclear DNA? Give three reasons.
c) Give two examples of molecules that protect cells against reactive oxygen species and explain how tey do so.
As before, I'll try to stick to the point.
7) Second messengers are formed from PI simply via phosphorylation. PIP is used to recruit proteins necessary to bring substances up to the cell membrane, PIP2 is vital for endosomal fusion and fission, and general endomembrane homeostasis, PIP3 is downstream of AKT, and is involved in processes related to cell survival and growth.
9) A gain-of-function mutation is one where a mutation in the tumor's genetic code has given it some form of capacity to perform a function. For example, it may have gained the capacity to breach into blood vessels. Some gain-of-function mutations have direct effects on protein: structural alterations to a protein can help it better function. Conversely, it might actually cause a certain protein to become useless, but is still considered a gain-of-function because such a protein may have had been an inhibitor of another protein which is now free to function. In this sense, gain-of-function mutations can have similar direct effects on proteins with drastically different cellular function outcomes.
Some gain of function mutations are random - rapid replication without checkpoints means more genetic mistakes. A few wrong codons may shorten, lengthen or change the structure ...
The solution discusses the gan-of-function mutations in molecular and cell biology.