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March 29, 2024, 07:21:34 am

Author Topic: VCE Biology Question Thread  (Read 3570918 times)  Share 

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Joseph41

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Re: VCE Biology Question Thread
« Reply #11700 on: May 28, 2019, 03:31:05 pm »
0

 haha I just realised that I forgot to add background info on that but thank you so much doing it much appreciated

Background info looks great now. :)

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sarah15

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Re: VCE Biology Question Thread
« Reply #11701 on: May 29, 2019, 06:00:58 pm »
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Hi, I was wondering if it is necessary to know the types of pathogens the various immune cells eliminate. Do neutrophils engulf bacteria, or would it be better to say microbes?

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Re: VCE Biology Question Thread
« Reply #11702 on: May 29, 2019, 06:11:00 pm »
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Hi, I was wondering if it is necessary to know the types of pathogens the various immune cells eliminate. Do neutrophils engulf bacteria, or would it be better to say microbes?
It depends a bit on the context. In general, it's a good idea to be as specific as possible - but you also have to avoid being so specific that you're wrong.

Normally the question you're answering will tell you what pathogen is involved in the stem of the question. If it tells you, then use that. Neutrophils engulf bacteria, but you could just say that they engulf extracellular pathogens and you'd be fine. I'd recommend using pathogen rather than microbe though if you want to use a more general term because you're better off using the same terminology that is used in the study design.
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Re: VCE Biology Question Thread
« Reply #11703 on: May 29, 2019, 07:28:11 pm »
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hi! I was a little confused as to why antibody levels are not at zero before given any immunisation??
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Re: VCE Biology Question Thread
« Reply #11704 on: May 29, 2019, 07:39:16 pm »
+4
hi! I was a little confused as to why antibody levels are not at zero before given any immunisation??

Because there may have been prior exposure to the particular antigen and hence some antibodies may be present in the blood prior to immunisation. (immunisation may be booster dose).

Could also refer to antibodies in general, in which case the body may have passively, but naturally acquired antibodies via the placenta, mother's milk from breastfeeding, or other form of antibody acquisition.

Edit: beaten. Also, memory cells! (like jack.cameron said)
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vox nihili

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Re: VCE Biology Question Thread
« Reply #11705 on: May 29, 2019, 08:21:10 pm »
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hi! I was a little confused as to why antibody levels are not at zero before given any immunisation??

Also just because the cells are already there and do pop out a few antibodies even before they've ever been activated, but this is probably not really something to worry about in VCE.
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Re: VCE Biology Question Thread
« Reply #11706 on: May 29, 2019, 10:15:10 pm »
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Can someone please explain the role of B memory cells during re infection?

What do they do? secrete antibodies or proliferate into B plasma cells and more B memory cells?

Thanks.
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Erutepa

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Re: VCE Biology Question Thread
« Reply #11707 on: May 30, 2019, 08:28:27 am »
+5
Can someone please explain the role of B memory cells during re infection?

What do they do? secrete antibodies or proliferate into B plasma cells and more B memory cells?

Thanks.
when naive b cells are exposed to its specific antigen and receives the necessary costimulation from its corresponding t helper cell, it will differentiate and proliferate. Most of the cells produced from this differentiation are plasma b cells which produce antibodies in large quantities, however memory b cells are also produced. While these plasma b cells are only short lived (they will undergo apoptosis when infection is gone) memory b cells are much longer lived. As such they function to remain resident in the body such to contribute to a faster and stronger secondary immune response to their specific antigen.
In this secondary antigen exposure they will be activated much like a naive b cell (also requiring that t helper cell interaction) and will similarly differentiate and proliferate into plasma and more memory. The reason this secondary response is faster and stronger is that there is simply a greater number of memory b cells for a specific antigen in these secondary infections than there would have been niave b cells in the primary exposure to the antigen.

Hope this helps and please note that this depth of knowledge is not all that relevant to the course. But it is good to try to understand the processes in a bit of extra depth.
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sarah15

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Re: VCE Biology Question Thread
« Reply #11708 on: May 31, 2019, 06:43:10 pm »
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Are the mucous membranes an example of a physical AND chemical barrier to pathogens? Physical because they trap pathogens and chemical because they secrete mucus?

Erutepa

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Re: VCE Biology Question Thread
« Reply #11709 on: May 31, 2019, 08:08:51 pm »
+1
Are the mucous membranes an example of a physical AND chemical barrier to pathogens? Physical because they trap pathogens and chemical because they secrete mucus?
The mucus itself is not so much a chemical barrier. It is more a physical barrier in that it physically prevents pathogens from entering the body. Chemical barriers would be digestive enzymes that might be secreted in mucosal membranes, but are not the mucosal membrane itself. One of these is lysozyme
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Re: VCE Biology Question Thread
« Reply #11710 on: June 01, 2019, 06:35:08 pm »
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Is it compulsory to specify that there is a specific receptor whose shape is complementary to the signalling molecule or is it ok to just write 'specific receptor'?

Does it depend?
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Erutepa

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Re: VCE Biology Question Thread
« Reply #11711 on: June 01, 2019, 10:30:18 pm »
+5
Is it compulsory to specify that there is a specific receptor whose shape is complementary to the signalling molecule or is it ok to just write 'specific receptor'?


Does it depend?
I'm not sure what exactly examiners are looking for, but I would personally write 'complimentary shaped receptor' to highlight that role of structure in function.
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Re: VCE Biology Question Thread
« Reply #11712 on: June 01, 2019, 11:07:01 pm »
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Bit late to the party but real quick can someone tell me the difference between Natural killer cells and cytotoxic T cells. I know cytotoxic T cells are specific yes but how or what sets them apart from natural killer cells.
Edit: "what does cytotoxic T  cells set apart from cytotoxic T cells lmfao"
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Erutepa

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Re: VCE Biology Question Thread
« Reply #11713 on: June 02, 2019, 07:13:19 am »
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Bit late to the party but real quick can someone tell me the difference between Natural killer cells and cytotoxic T cells. I know cytotoxic T cells are specific yes but how or what sets them apart from cytotoxic T cells.
Cytotoxic t cells are specific in That they possess TCRs complimentary to a certain antigen. Once activated by t helper cells and dendritic cells, they will bind to their specific antigens when nestled in mhc class 1 receptors.
Nk cells don't bind to a specific antigen, rather they bind to the mhc class 1 receptor itself. When they bind to mhc class 1 they are suppressed, whereas if no mhc class 1 is present on the cell (like bacterium), they will carry out their function to kill the cell.

So cytotoxic T cells = specific antigen within mhc class 1
Natural killer cells = mhc class 1 protein itself
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Re: VCE Biology Question Thread
« Reply #11714 on: June 02, 2019, 10:44:21 am »
+1
Bit late to the party but real quick can someone tell me the difference between Natural killer cells and cytotoxic T cells. I know cytotoxic T cells are specific yes but how or what sets them apart from cytotoxic T cells.

Here's also some other information if you're interested

This is outside of the scope of the VCE course, but its some extra interesting info about it and you can find it in the Nature of Biology textbook if you use it. So basically, Natural Killer cells have two receptors, a killer activation receptor (KAR) and killer inhibitory receptor (KIR). KAR binds with surface proteins released by virally infected cells or cancerous cells in distress, while KIR binds to MHC Class I markers on the cell. If the KIR binds with a sufficient number of MHC Class I markers, then the order to kill is overridden. (We can get a lack of MHC Class I markers when viruses or cancer cells inhibit or destroy MHC Class I markers on the cell surface). Therefore, if the cell is lacking of MHC Class I markers, then the signal to kill won't be overridden and then the NK cell will secrete perforin damaging the plasma membrane leading to lysis. If the cell has sufficient MHC Class I markers, then I'm pretty sure that those cells are left for cytotoxic T cells.
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