The Student Room Group

OCR june 8th Biology revision thread

for everyone taking the exam!
any ideas on topics which may come up?
Reply 1
???????
Reply 2
everything in the book, have a look at past papers
I am so sick of this exam, this is my third time taking it, because my teacher thinks i can do better, I already have an A in it!

From my experience the long answer questions are always on conservation, food and health and stuff like that.

In the first exam there was hardly any biological molecules and loads of food and health, the second there was a 50/50 split, but it may change again.

There will always be a Q on immunity!
Reply 4
you already have an A!

This ones worth more though isnt it (50%) so I really need to do well on it

can anyone help with the B and T lymphocyte response? im really confused!
When a pathogen enters the body it has antigens on it's surface these act as foreign markers. Colonal selection takes place in which the correct T lymphocytes and B lymphocytes are selected. (at this point the Tymphocytes and Blymphocytes are unspeicalised) Then colonal expansion takes place ( this is when the B lymphocytes and T lymphoctes divide by mitosis.)

Differentation then takes place -T lymphocytes differentiate into Tkiller cells T helper cells and T memory cells.

For Differentation of B cells to take place they need stimulation therefore T cells and macrophages release interlukines that help stimulate differentation. The B cells then divide into plasma cells and B memory cells.

* T killer cell destroy pathogens by releasing toxins such as hydrogen peroxide to bind to receptors and destory it.

*T helper cells relase interlukines that activate B cells

* Plasma cells produce and relase antibodies that bind to complimentary antigens and nuetralise them
*T and B memory cells remember the specific antigen and remian in the blood so if the same antigen invades again they will recognise teh antigen and will be able to select the correct B and T lymphocytes quickly (thus explaining why the secondary response is quicker)
.....hope this helps :smile:

Can anyone help me with conservation ? it's really boring and takes me ages to remember ....does anyone know how likely it is to come up?
Reply 6
when you have a pathogen there are specific T and B lymphocyes for the antigen.

but do both specific T and B lymphocyes act together or does a Specific T lymphocye acts first ie clonal selection etc and the the B lymphocyte?
Reply 7
that was really helpful,
however i dont get when b lymphcytes are used and when t lymphctyes are.
i get the process however what causes the different type of lynphcyte to be used?
Erm yeah i was asking my teacher about which happens first B or T lymphocytes and i think she basically said that they can all work at basically the same time but diffentation for B lymphocyes may happen slighty after the differntation of T lymphocytes due to the need of B lymphocytes to be stimulated by interluekin in order to differentiate ..however things Like T killer cells and antibodies can be working at the same time
Reply 9
both B and Th cells must come into contact with a specific antibody's antigen (not necessarily the same antigen though) , the process is a little more complicated than the book tells but I think the B cell presents parts of the antigen on its surface and if a complementary Th cell comes along then it will release the interleukins and then B cell will be activated.

It's like a backup system to ensure the B cell isn't activated to easily - prevents auto immune.

I don't think you should mention any of this in the exam however.. It wont be in the mark scheme. But i hope it helps understanding :smile:

My source is the khan academy.