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March 29, 2024, 10:03:05 am

Author Topic: VCE Biology Question Thread  (Read 3571033 times)  Share 

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interessant

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Re: VCE Biology Question Thread
« Reply #11670 on: May 21, 2019, 06:44:52 pm »
+1
Oh ok, I see, thank you so much!

Chocolatemilkshake

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Re: VCE Biology Question Thread
« Reply #11671 on: May 21, 2019, 07:00:18 pm »
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Hi everyone,

Would love some help with these few questions about the immune system...

1. Do Helper T cells and Cytotoxic T cells have receptors specific to foreign antigens or are the simply specific to the MHC I/MCH II markers on the cell surface? Eg. in order to bind to cell MHC I marker, recognise it as foreign and stimulate apoptosis, does a cytotoxic T cell need a receptor specific to this antigen?

2. I know that once Helper T cells find an antigen they are specific to, that they release interleukins causing them to proliferate themselves and B-cells/Cytotoxic T cells. However, for the activation of either the B cells or Cytotoxic T cells, does the B cell/Cytotoxic T cell first need to bind to the foreign antigen and then the interleukins stimulate their proliferation?

I hope it isn't too hard to understand what I'm trying to ask. Once again thanks for all your help :)

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vox nihili

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Re: VCE Biology Question Thread
« Reply #11672 on: May 21, 2019, 07:51:18 pm »
+7
Hi everyone,

Would love some help with these few questions about the immune system...

1. Do Helper T cells and Cytotoxic T cells have receptors specific to foreign antigens or are the simply specific to the MHC I/MCH II markers on the cell surface? Eg. in order to bind to cell MHC I marker, recognise it as foreign and stimulate apoptosis, does a cytotoxic T cell need a receptor specific to this antigen?

2. I know that once Helper T cells find an antigen they are specific to, that they release interleukins causing them to proliferate themselves and B-cells/Cytotoxic T cells. However, for the activation of either the B cells or Cytotoxic T cells, does the B cell/Cytotoxic T cell first need to bind to the foreign antigen and then the interleukins stimulate their proliferation?

I hope it isn't too hard to understand what I'm trying to ask. Once again thanks for all your help :)



1. The MHC molecules just hold the antigen. So the receptors are specific to the antigen, but can only see the antigen if it's being held in an MHC molecule.

2. This is a really intelligent question that goes beyond the course. You're quite right though. T-helper cells help other kinds of cells proliferate. Those B-cells or Tc-cells need to bind their antigen to proliferate though (otherwise how do you choose which ones to make proliferate!).
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Chocolatemilkshake

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Re: VCE Biology Question Thread
« Reply #11673 on: May 21, 2019, 08:24:17 pm »
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1. The MHC molecules just hold the antigen. So the receptors are specific to the antigen, but can only see the antigen if it's being held in an MHC molecule.

2. This is a really intelligent question that goes beyond the course. You're quite right though. T-helper cells help other kinds of cells proliferate. Those B-cells or Tc-cells need to bind their antigen to proliferate though (otherwise how do you choose which ones to make proliferate!).

Wow! Thanks so so much this really helps! Just checking... so both the T-cell and the B-cell or Tc-cell would need to bind to the same specific foreign antigen in order to initiate the proliferation? Does the Helper T cell and B-cell or Cytotoxic T cell have to bind to exactly the same foreign antigen, or can be the same antigen but found on different sides of the body?

Also, do the Helper T cells and B-cells or Cytotoxic T cells always bind to free floating foreign pathogens/antigens or can they bind to the foreign antigens presented on MHCII by APCs?

And what is the significance of B-cells having MHC II markers?

Sorry about the extra questions, I really appreciate your answers
« Last Edit: May 21, 2019, 08:39:21 pm by Chocolatemilkshake »
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vox nihili

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Re: VCE Biology Question Thread
« Reply #11674 on: May 21, 2019, 08:50:27 pm »
+2
Wow! Thanks so so much this really helps! Just checking... so both the T-cell and the B-cell or Tc-cell would need to bind to the same specific foreign antigen in order to initiate the proliferation? Does the Helper T cell and B-cell or Cytotoxic T cell have to bind to exactly the same foreign antigen, or can be the same antigen but found on different sides of the body?

Also, do the Helper T cells and B-cells or Cytotoxic T cells always bind to free floating foreign pathogens/antigens or can they bind to the foreign antigens presented on MHCII by APCs?

And what is the significance of B-cells having MHC II markers?

Sorry about the extra questions, I really appreciate your answers

They need to bind the same kind of antigen, but not exactly the same one (as in, the antigens should be identical but they don't both bind to exactly the same molecule).

They can only bind to antigens presented on MHC molecules, as above.

They present antigens to T-cells, this is beyond VCE though.
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Chocolatemilkshake

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Re: VCE Biology Question Thread
« Reply #11675 on: May 21, 2019, 09:26:03 pm »
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They need to bind the same kind of antigen, but not exactly the same one (as in, the antigens should be identical but they don't both bind to exactly the same molecule).

They can only bind to antigens presented on MHC molecules, as above.

They present antigens to T-cells, this is beyond VCE though.

Thanks so much this makes a lot more sense now and is really interesting stuff
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DBA-144

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Re: VCE Biology Question Thread
« Reply #11676 on: May 21, 2019, 10:15:56 pm »
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Just to clarify, T helper cells can only bind to antigens presented on MHC II markers, whereas B cells can bind to free antigens. Can cytotoxic T cells also bind to free antigens?

vox, are you saying that all lymphocytes can only bind to free antigens?

Sorry for hijacking the discussion.
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vox nihili

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Re: VCE Biology Question Thread
« Reply #11677 on: May 21, 2019, 10:42:05 pm »
+4
Just to clarify, T helper cells can only bind to antigens presented on MHC II markers, whereas B cells can bind to free antigens. Can cytotoxic T cells also bind to free antigens?

vox, are you saying that all lymphocytes can only bind to free antigens?

Sorry for hijacking the discussion.


T-cells bind to antigens presented in the context of MHC molecules. Class I for cytotoxic T-cells and class II for T-helper cells. Under no circumstances can T-cells bind to free antigen, they simply don't have the receptors for it.

B-cells, on the other hand, only bind to free antigen. They do not bind to antigen in the context of an MHC molecule.
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Chocolatemilkshake

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Re: VCE Biology Question Thread
« Reply #11678 on: May 22, 2019, 07:03:54 am »
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T-cells bind to antigens presented in the context of MHC molecules. Class I for cytotoxic T-cells and class II for T-helper cells. Under no circumstances can T-cells bind to free antigen, they simply don't have the receptors for it.

B-cells, on the other hand, only bind to free antigen. They do not bind to antigen in the context of an MHC molecule.

Does that mean that in order to proliferate, a Cytotoxic T cell would need to find an antigen on MHC I while a Helper T cell would find that same antigen on MHC II and then release cytokines activating the cytotoxic T cell causing it to clone? Or can the Cytotoxic T cell find antigens on MHC II but after it is activated only work on MHC I?

Thanks again
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DBA-144

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Re: VCE Biology Question Thread
« Reply #11679 on: May 22, 2019, 07:37:57 am »
+1
Does that mean that in order to proliferate, a Cytotoxic T cell would need to find an antigen on MHC I while a Helper T cell would find that same antigen on MHC II and then release cytokines activating the cytotoxic T cell causing it to clone? Or can the Cytotoxic T cell find antigens on MHC II but after it is activated only work on MHC I?

Thanks again

First bit seems right to me.
Second bit: Don't think so. Cytotoxic T cells can only bind to MHC I; I cannot see why finding an antigen on MHC II markers followed by the release of cytokines by T helper cells would cause a change in the shape, function or structure of the cytotoxic t cell receptors. This just an educated guess though, it is quite likely i am wrong :P
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vox nihili

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Re: VCE Biology Question Thread
« Reply #11680 on: May 22, 2019, 10:01:45 am »
+4
Does that mean that in order to proliferate, a Cytotoxic T cell would need to find an antigen on MHC I while a Helper T cell would find that same antigen on MHC II and then release cytokines activating the cytotoxic T cell causing it to clone? Or can the Cytotoxic T cell find antigens on MHC II but after it is activated only work on MHC I?

Thanks again

DBA-144 is right. To be clear, this is probably starting to steer a little away from VCE, so don't stress too much if you're a bit confused by the nuances of this.
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Re: VCE Biology Question Thread
« Reply #11681 on: May 22, 2019, 06:10:58 pm »
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I've tried googling this, and I don't know if I'm overthinking it because I've seen some diagrams but I don't think they really match the question. Would someone be able to help me with this question please

Draw a diagram to show how antibodies disarm antigens by forming a lattice

Thanks!
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Re: VCE Biology Question Thread
« Reply #11682 on: May 22, 2019, 06:21:16 pm »
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I've tried googling this, and I don't know if I'm overthinking it because I've seen some diagrams but I don't think they really match the question. Would someone be able to help me with this question please

Draw a diagram to show how antibodies disarm antigens by forming a lattice

Thanks!
Antibodies can bind to antigens in such a way to cause agglutination - essentially 'clumping' antigens together or forming a lattice
You can find some good example images from a quick google. here is one:

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Re: VCE Biology Question Thread
« Reply #11683 on: May 22, 2019, 07:53:06 pm »
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Where are memory b cells located?

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Re: VCE Biology Question Thread
« Reply #11684 on: May 23, 2019, 07:03:34 pm »
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Can someone outline the stimulus-response model in signal transduction? An example would be nice.  :)
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