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June 18, 2019, 09:31:27 pm

Author Topic: VCE Biology Question Thread  (Read 1234789 times)  Share 

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f0od

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Re: VCE Biology Question Thread
« Reply #11670 on: May 19, 2019, 01:32:57 pm »
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Why do plants (or chickpeas in this case) consume more oxygen when they are germinating as opposed to when they are not germinating?

Thankss
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zuijinde

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Re: VCE Biology Question Thread
« Reply #11671 on: May 19, 2019, 02:07:44 pm »
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Why do plants (or chickpeas in this case) consume more oxygen when they are germinating as opposed to when they are not germinating?

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Not too sure, but I suppose it's something to do with its dormancy cycle. Dormancy is when an organism limits its metabolism to conserve energy, so when they germinate, they probably need more oxygen to compensate when they were dormant.

brigmarks

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Re: VCE Biology Question Thread
« Reply #11672 on: May 19, 2019, 02:40:21 pm »
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Hi!
For my depth study, I am investigating DNA profiling and I am trying to nail down some of the basics. However, I am confused about the following questions:
Are introns located in genes or between genes?
If introns are cut out of the new mRNA strand during splicing and broken down into nucleotides to be used again, how are they used in DNA profiling?

Thanks!

Hey! Sounds like a really cool in depth study topic!
- So introns are located within genes- the name intron comes from 'intragenic region' and these are spliced out during intron splicing

- The process of DNA profiling means that DNA molecules (not mRNA strands) are being tested for their coding so it doesn't matter what is being removed from RNA, scientists are just concerned with everything contained within the DNA

- The reason introns are tested is that exons (which code for useful proteins) can't be drastically different/ mutated between people because we need properly working proteins to survive and mutations in exons might mean that an organism cant survive, but mutations in introns don't impact the survivability of the organism, because these occur randomly. Over time, there is more genetic difference in introns than for exons, (these can be silent mutations), meaning these introns can be used to identify people e.g. by linking them to crime scenes and determining relatedness (because these randomly mutated, different introns are heritable)

Hope that helps and good luck with your in depth study!!

almondsforlife

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Re: VCE Biology Question Thread
« Reply #11673 on: May 20, 2019, 09:34:57 pm »
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Hello hello :)
does anyone have any ways to improve experimental accuracy? It's how close your result is to the true value, and I absolutely can't think of any ways. Whatever I think of end up falling in either validity or reliability.

Owlbird83

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Re: VCE Biology Question Thread
« Reply #11674 on: May 21, 2019, 05:57:29 pm »
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Hello hello :)
does anyone have any ways to improve experimental accuracy? It's how close your result is to the true value, and I absolutely can't think of any ways. Whatever I think of end up falling in either validity or reliability.

Maybe by using really accurate measuring devices, such as if you are weighing something, you want a scale with more decimal places, or if you are measuring temperature you want a digital thermometer that is more accurate than a regular one.
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almondsforlife

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Re: VCE Biology Question Thread
« Reply #11675 on: May 21, 2019, 06:44:52 pm »
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Oh ok, I see, thank you so much!

Chocolatemilkshake

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Re: VCE Biology Question Thread
« Reply #11676 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 #11677 on: May 21, 2019, 07:51:18 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 :)



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 #11678 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 #11679 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 #11680 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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Re: VCE Biology Question Thread
« Reply #11681 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.

vox nihili

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Re: VCE Biology Question Thread
« Reply #11682 on: May 21, 2019, 10:42:05 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.


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 #11683 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 #11684 on: May 22, 2019, 07:37:57 am »
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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