VCE Biology Question Thread

[Dkontro]

How would you control the spread of a bacterial disease if only one person had the disease compared to many?
Had this question on the SAC. No information was given about the bacteria

[IndefatigableLover]

Which companies are the best (for Unit 3) when it comes to Biology?

[grannysmith]

I have a question about MHC markers

What's the MAIN difference between class 1 and class 2 MHC markers? Is it only that class 1 are on the surface of every nucleates cell, whereas class 2 are only on APCs?

If so, how does the body distinguish between self or non self cells? Does the MHC marker bind to antigens or is the MHC marker the actual thing that signifies self?

It's quite a complex area of biology that isn't covered to much depth in VCE. However, my understanding is that MHC markers aid in the the recognition of self and the detection of non self. Now, there are two types of MHC dealt in VCE: Class I and Class II. Because only a special group of immune cells, called APCs, possess these MHC II markers, they don't really function as a self marker. Rather, this is the job of MHC I since all nucleated cells have them. Now, I don't think that the MHC marker itself acts as a 'self' molecule. Instead, they continuously present fragments of molecules found within a cell. If it so happens that a particular cell, for example, is virally infected, then viral particles will be presented on the MHC marker. This will then be detected by an NK or T cell and hence  be identified as foreign (and subsequently destroyed). So it's not a matter of detecting 'self' than it is of detecting non self. You only need one mechanism and you've got it covered.

Now, I have to say that I'm in no way an expert, and this is purely my understanding - which is perhaps flawed. Because I myself have always wondered that if it's only a matter of  detecting foreign antigens, which is inherently a 'specific' mechanism of the immune system, then how do 'non specific' immune cells such as your neutrophils and macrophages detect non self material? They don't have specific receptors to antigens so is it just the absence of self molecules in this instance?

@Dkontro
You could perhaps isolate the infected person from everyone else until their symptoms/infective period has subsided. If it's on a large scale, then you'd need antibiotics as isolation would not be possible.

@IndefatigableLover
I found STAV, Neap to be top notch. Following would probably be Insight/TSSM then Lisachem.

[biy]

It's quite a complex area of biology that isn't covered to much depth in VCE. However, my understanding is that MHC markers aid in the the recognition of self and the detection of non self. Now, there are two types of MHC dealt in VCE: Class I and Class II. Because only a special group of immune cells, called APCs, possess these MHC II markers, they don't really function as a self marker. Rather, this is the job of MHC I since all nucleated cells have them. Now, I don't think that the MHC marker itself acts as a 'self' molecule. Instead, they continuously present fragments of molecules found within a cell. If it so happens that a particular cell, for example, is virally infected, then viral particles will be presented on the MHC marker. This will then be detected by an NK or T cell and hence  be identified as foreign (and subsequently destroyed). So it's not a matter of detecting 'self' than it is of detecting non self. You only need one mechanism and you've got it covered.

Now, I have to say that I'm in no way an expert, and this is purely my understanding - which is perhaps flawed. Because I myself have always wondered that if it's only a matter of  detecting foreign antigens, which is inherently a 'specific' mechanism of the immune system, then how do 'non specific' immune cells such as your neutrophils and macrophages detect non self material? They don't have specific receptors to antigens so is it just the absence of self molecules in this instance?

@Dkontro
You could perhaps isolate the infected person from everyone else until their symptoms/infective period has subsided. If it's on a large scale, then you'd need antibiotics as isolation would not be possible.

@IndefatigableLover
I found STAV, Neap to be top notch. Following would probably be Insight/TSSM then Lisachem.

Thank you man! <3

So for VCE, we just need to know the two different types of markers, and the fact that class 1 is on nucleated cells, and class 2 is on Antigen Presenting Cells? Nothing more?

Also how can I view the study guide thing which actually tells you what we need to know, and what not to know. So that I dont have to continually ask AN <3

[grannysmith]

Thank you man! <3

So for VCE, we just need to know the two different types of markers, and the fact that class 1 is on nucleated cells, and class 2 is on Antigen Presenting Cells? Nothing more?

Also how can I view the study guide thing which actually tells you what we need to know, and what not to know. So that I dont have to continually ask AN <3

Yes, that's right Their functions should also be known though.

Are you talking about the study design? It's not terribly explicit in what exactly is required knowledge. But if you click here http://www.vcaa.vic.edu.au/Pages/vce/studies/biology/biologyindex.aspx you'll find the SD under 'Curriculum' and the Biology FAQs under 'Support Material'.

[biy]

Yes, that's right Their functions should also be known though.

Are you talking about the study design? It's not terribly explicit in what exactly is required knowledge. But if you click here http://www.vcaa.vic.edu.au/Pages/vce/studies/biology/biologyindex.aspx you'll find the SD under 'Curriculum' and the Biology FAQs under 'Support Material'.

Ah thanks for that man <3

What exactly is their function, then?
Also how do antibodies and T cell receptors differ in detecting and responding to an antigen? I said that antibodies actually bind to the antigenic particles, where as T cell receptors can only bind to the antigen if they are presented on MHC markers from APCs. If this is true, how can I answer the second part of the question, about how they respond after the antigen-receptor complex?

Thanks Granny Smith, your ethylene is definitely overproducing
That was a lame joke, but oh well

[alchemy]

Which companies are the best (for Unit 3) when it comes to Biology?

Neap and STAV were quite good from memory. Neap was the hardest in terms of difficulty I found.
Insight was on the easier side, but still good.
Lisachem wasn't all that great tbh....

[grannysmith]

Ah thanks for that man <3

What exactly is their function, then?
Also how do antibodies and T cell receptors differ in detecting and responding to an antigen? I said that antibodies actually bind to the antigenic particles, where as T cell receptors can only bind to the antigen if they are presented on MHC markers from APCs. If this is true, how can I answer the second part of the question, about how they respond after the antigen-receptor complex?

Thanks Granny Smith, your ethylene is definitely overproducing
That was a lame joke, but oh well

Hahaha - nice one.

Function of MHC? To present molecules, which could include foreign antigens, to appropriate T cells in order to elicit a specific immune response. The type of MHC determines which type of T cell is involved.

Remember that B cells have antibodies on their surface which function as receptors. However, the same antobodies are produced during the humoral response which are then released as free-floating antibodies.
You're right in that antibodies bind directly to antigens whereas T cells can only bind to antigens expressed on MHC (using their receptors). However, T helper cells cans only bind to those on MHC II whereas cytotoxic T cells can bind to those on MHC I. Therefore the action of  T helper cells depends on the activity of APCs. Once this occurs, the T helper cell is 'activated' and release cytokines (chemical signalling molecules) which subsequently activate the cell mediated/humoral response. Recall that B cells are relatively non-functional without the aid of T helper cells.

[StupidProdigy]

What's the role of the helper t cell in the humoral response? Is it the stimulation of b plasma cells?

[Reus]

What's the role of the helper t cell in the humoral response? Is it the stimulation of b plasma cells?

Yep that's right but you also need to mention - as it is a significant function, that they also activate cytotoxic T cells (which have their own distinct function) in the cell mediated response.

[alchemy]

Hahaha - nice one.

Function of MHC? To present molecules, which could include foreign antigens, to appropriate T cells in order to elicit a specific immune response. The type of MHC determines which type of T cell is involved.

Remember that B cells have antibodies on their surface which function as receptors. However, the same antobodies are produced during the humoral response which are then released as free-floating antibodies.
You're right in that antibodies bind directly to antigens whereas T cells can only bind to antigens expressed on MHC (using their receptors). However, T helper cells cans only bind to those on MHC II whereas cytotoxic T cells can bind to those on MHC I. Therefore the action of  T helper cells depends on the activity of APCs. Once this occurs, the T helper cell is 'activated' and release cytokines (chemical signalling molecules) which subsequently activate the cell mediated/humoral response. Recall that B cells are relatively non-functional without the aid of T helper cells.

Nice! I can't believe you still remember all this detail from bio haha. It's all just slipped through my head since last year lol...

[StupidProdigy]

Yep that's right but you also need to mention - as it is a significant function, that they also activate cytotoxic T cells (which have their own distinct function) in the cell mediated response.

Thanks Reus
What if the question is asking about the humoral response only?? I don't understand why I should mention the cytotoxic T cells if they're not in it aha (they're not right?  )

[HighTide]

Thanks Reus
What if the question is asking about the humoral response only?? I don't understand why I should mention the cytotoxic T cells if they're not in it aha (they're not right?  )

T Helper cells can stimulate proliferation of B cells and T cells. They do this by secreting Cytokines, in particular Interleukin 2. This is why they are called "Helper cells". They help the immune response and are the link between the humoral and cell-mediated responses (can regulate B cell and T cell activity). No need to mention cytotoxic T cells, the question is probably asking about cytokines.
Hope it helps. 

[KingDrogba]

How many marks can you afford to drop in both the sacs (out of 200) and the end of year exam to get a 50?

[plants]

Hey guys,

Can helper t-cells stimulate both b-cells and cytotoxic t-cells at the same time?

thanks,

EDIT: and on that note, how do t-helper cells know which b-cells have the right antibodies on their surface complementary to the antigen and hence stimulate them to proliferate?