Edexcel A2 Biology Unit 4(6BIO4) 13/06/11 - OFFICIAL THREAD !

Hope so, thanks and same to you



Cheers



Do you reckon they could also ask stuff from unit 1?

I have no idea.

The spec is pretty vague and it just says:

Non-specific responses of the body to infection
12 Describe the non-specific responses of the body to infection, including inflammation, lysozyme action, interferon, and phagocytosis.

The specific immune response
13 Explain the roles of antigens and antibodies in the body’s immune response including the involvement of plasma cells, macrophages and antigen-presenting cells.

14 Distinguish between the roles of B cells (including B memory and B effector cells) and T cells (T helper, T killer and T memory cells) in the body’s immune response.

In jan 10 they talked about CD4 receptors and HIV. So you never know, just learn everything from the book.

thank you so much!! But isn't the info too simple? What about MHC APC complexes, C4 receptors ???

what I don't understand you see how b-cells and macrophages can actually engulf pathogens, so what's the point of producing antibodies just kill them while they are inside the macrophage?

what I don't understand you see how b-cells and macrophages can actually engulf pathogens, so what's the point of producing antibodies just kill them while they are inside the macrophage?

In jan 10 they talked about CD4 receptors and HIV. So you never know, just learn everything from the book.

In jan 10 they talked about CD4 receptors and HIV. So you never know, just learn everything from the book.

Because antibodies only HELP clear an infection, the pathogens are still phagocytosed in the end. E.g. each antibody has two binding sites, so two pathogens can bind to the antibody at the same time - the pathogens become clumped together. Phagocytes e.g. macrophages then bind to the antibodies and phagocytose the pathogens at once.

OR

e.g. antibodies can bind to toxins produced by pathogens, this prevents the toxins from affecting human cells, so the toxins are neturalised, the toxin-antibody complexes are then also phagocytosed.

Hope that helps!

are the only past papers available for this unit
jan 10
june 10
jan 11
???

are there no 09 papers?

I hope there is less immunity

Has anyone put on revision notes? I can't find any. This exam is going to be a nightmare, along with Core 3!

heyy everyone

jus done a paper and skimmed thru the stuff i can do frm memory...
do you think its best to do moreeee revision to memorise things and then be able to do papers

orrr

just do what you can and then use the mark scheme to knw wha the answers are and learn thatt?!!!

please reply/help!!!

What are selection pressures? Are they abiotic/biotic factors that affect reproduction???

Yep and depending on what the selection pressures are in the environment, different alleles are advantageous and disadvantageous. More advantageous alleles = more likely to survive etc etc.

Thanks again! What is the primary response and the secondary response with respect to antigens and anitbodies (relating to june 2010 mark scheme q4b ii )?

Haven't looked at ques, coz I'm buzy making condensed notes, but from my memory..

primary response: first time your immune system comes across a pathogen. takes time to make antibodies etc. etc. so you feel ill (have symptoms)

secondary response: when you re-encounter the same pathogen, but as you got memory cells and antibodies from before, they quickly recognise the pathogen's antigens and the body is able to conjure up a faster stronger response.