VCE Biology Question Thread

[biy]

-The innate immunological response is fixed and cannot adapt to the target presented. This is because it is based on inherited traits passed on from parents. In this way they cannot change. (In contrast for adaptive immunity cells they undergo a genetic lottery shuffle thing where they select different combinations of DNA and get rid of the rest. So this means that adaptive immune cells have a different set of DNA from other cells in the body.) There are specific receptors on the surface of phagocytic cells which can recognise pathogen structures. These pathogen structures tend to be repetitive sequences that could be found in viral RNA or DNA or in bacteria specific carbohydrates or pathogen specific wall components.

-Im pretty sure MHC markers don't bind with other MHC markers. MHC markers bind to T-cell receptors. MHC markers are like flag proteins. They say hey I found a pathogen, come look (MHC II), or hey im infected by a virus (MHC I)

- An antigen is any foreign substance that elicits an adaptive immunity response, which could be any foreign substance because the T-cell receptors and B-cell receptors are kinda designed in a way so that there are a lot of different possibilities of what they can end up recognising as an antigen. Along with carbohydrates and proteins, i'm pretty sure even metals can be recognised as antigens. In cases where things go wrong and you produce a B-cell or T-cell that ends up recognising self cells as foreign, you get an autoimmune disease, and the targets would be known as autoantigens. An example of an autoimmune disease is type 1 diabetes where the immune system destroys the beta cells in the islets of of Langerhans resulting in a reduced ability to produce insulin.

A question I tried earlier stated that a person had an organ transplant, but later the body refused this organ, explain why this might have occurred.

The answer stated: The MHC markers on the organ transplant were not recognised the body's cells, hence it was treated as a foreign substance.

I understand this, but the MHC markers part? This is why i asked you if MHC markers of our body actually bind with other MHC markers of other cells?

Also with the antigen definition, does it ALWAYS have to be adaptive immunity? Because what if the pathogens are eliminated by only the second line of defence, including phagocytes and granulocytes?

Thanks for the detailed responses! <3

[heids]

hi
Just wondering if I failed 2 sacs in a row, what are my possible outcomes? Will be able to still get a ss of 35? or should I drop biology?
thanks

As always, it's about how you carry yourself from here - unit 3 SACs (so the first 5 SACs you do) are worth only 20% of the SS.  If you can pick it up in your future SACs and the exam, you still have a huge chance of that 35.

Is Biology stressing you out horribly, taking up ridiculous amounts of your time, and making your life not worth living?  If so, possibly drop it.  But if it's not too bad, like you're not doing great but it's not destroying the rest of your subjects, then I'd keep it; it's a great subject with so much valuable stuff to learn and really worth it!

Here comes the in flush of questions again

I'm not a toilet 'influx'
Can I just reiterate what's been said a number of times?  I'm not against people asking questions - it's great to ask! but I think first you should Google stuff.  Wikipedia is brilliant (and more reliable than us students who are answering) and reading through actually answers questions you hadn't thought of - and is just really interesting.  It's also a valuable skill - in uni you won't be able to ask all your questions, you've got to learn to research and find answers for yourself - including wading through papers three feet deep in big words and numbers, to try and find the relevant points.

Sorry if you had googled stuff before, I just that I always found it easy to forget that all this information is at your fingertips if you just search for it!

[grannysmith]

^even better, search your question on this biology thread. There's like a few years worth of history and the same questions are asked every year. I honestly learnt at least 1/2 the bio course from trawling through AN threads. You'll also pick up on the tips and tricks that you won't find anywhere else.

[jihan]

Looking for a tutor for HHD, legal studies, Psychology, English and global politics. Please need a female tutor

[biy]

Question: State the steps involved in the production of antibodies to a specific bacterium.
My answer:
1). The antigens on the bacterium bind with a specific transmembrane antibody on the B lymphocyte.
2). The antigen-antibody complex is engulfed by the B lymphocyte, where the bacterium is digested by lysosomes.
3). The antigen fragments are presented on MHC class II markers on the membrane of the B cell.
4). Th lymphocyte binds to the MHC marker, forming an TCR-MHC complex. This complex initiates cell proliferation, where clonal expansion occurs. 
5). Plasma B cells produce, rapidly, antibodies and secrete them into the body. The memory B cells migrate to the lymph nodes to become dormant until the specific pathogen re-invades.

Is what I said correct? Sorry about earlier, bangali_lok and grannysmith, I didn't mean to be ignorant I just read what google says, but it's completely irrelevant most of the times, and is super complex. I just guess you guys don't know how it feels that your teacher is useless, it's a hopeless feeling. Luckily i have this website to help me. So many thanks to you all <3

[biy]

Question: State the steps involved in the production of antibodies to a specific bacterium.
My answer:
1). The antigens on the bacterium bind with a specific transmembrane antibody on the B lymphocyte.
2). The antigen-antibody complex is engulfed by the B lymphocyte, where the bacterium is digested by lysosomes.
3). The antigen fragments are presented on MHC class II markers on the membrane of the B cell.
4). Th lymphocyte binds to the MHC marker, forming an TCR-MHC complex. This complex initiates cell proliferation, where clonal expansion occurs. 
5). Plasma B cells produce, rapidly, antibodies and secrete them into the body. The memory B cells migrate to the lymph nodes to become dormant until the specific pathogen re-invades.

Is what I said correct? Sorry about earlier, bangali_lok and grannysmith, I didn't mean to be ignorant I just read what google says, but it's completely irrelevant most of the times, and is super complex. I just guess you guys don't know how it feels that your teacher is useless, it's a hopeless feeling. Luckily i have this website to help me. So many thanks to you all <3

Please?

[grannysmith]

Question: State the steps involved in the production of antibodies to a specific bacterium.
My answer:
1). The antigens on the bacterium bind with a specific transmembrane antibody on the B lymphocyte.
2). The antigen-antibody complex is engulfed by the B lymphocyte, where the bacterium is digested by lysosomes.
3). The antigen fragments are presented on MHC class II markers on the membrane of the B cell.
4). Th lymphocyte binds to the MHC marker, forming an TCR-MHC complex. This complex initiates cell proliferation, where clonal expansion occurs. 
5). Plasma B cells produce, rapidly, antibodies and secrete them into the body. The memory B cells migrate to the lymph nodes to become dormant until the specific pathogen re-invades.

Is what I said correct? Sorry about earlier, bangali_lok and grannysmith, I didn't mean to be ignorant I just read what google says, but it's completely irrelevant most of the times, and is super complex. I just guess you guys don't know how it feels that your teacher is useless, it's a hopeless feeling. Luckily i have this website to help me. So many thanks to you all <3

Nah, don't worry! There's a reason behind everything - and there's definitely a reason why this thread is called a "Biology Question Thread'

Your explanation is good, if not slightly long-winded. Also try to include the involvement of T helper cells. E.g. A specific B cell binds to the antigens of the bacterium using its receptors. With the aid of an appropriate T helper cell, the B cell undergoes proliferation and differentiation into plasma cells and memory cells. The plasma cells produce antibodies that are specific to the bacterium's antigens.

[biy]

Nah, don't worry! There's a reason behind everything - and there's definitely a reason why this thread is called a "Biology Question Thread'

Your explanation is good, if not slightly long-winded. Also try to include the involvement of T helper cells. E.g. A specific B cell binds to the antigens of the bacterium using its receptors. With the aid of an appropriate T helper cell, the B cell undergoes proliferation and differentiation into plasma cells and memory cells. The plasma cells produce antibodies that are specific to the bacterium's antigens.

Thank you for that, grannysmith!

Last question, promise ():
How do phagocytes and granulocytes (basically the cells involved in the second line of defence) identify a forgein pathogen, or in other words a non-self cell? Is it fine in VCE bio to just say that the MHC class 1 markers of these cells do not recognise the markers of the pathogens, hence are labelled as non-self? Also are antigens only specific to the third line of defence?


Thank you so much

[grannysmith]

Thank you for that, grannysmith!

Last question, promise ():
How do phagocytes and granulocytes (basically the cells involved in the second line of defence) identify a forgein pathogen, or in other words a non-self cell? Is it fine in VCE bio to just say that the MHC class 1 markers of these cells do not recognise the markers of the pathogens, hence are labelled as non-self? Also are antigens only specific to the third line of defence?


Thank you so much

Okay, last answer (for today)

From the VCAA 2008 Bio Exam (U3):

Question 5
Normally in mammals, if tissue from another individual enters the body, the foreign cells are recognised as
‘non-self’ by the immune system. The tissue is then rejected unless special drugs are used.
a. i. Which cells of the immune system are initially responsible for recognising non-self cells introduced
by an organ transplant?

From the assessment report:
Any one of:
• T-helper cells
• macrophages/phagocytes
• antigen presenting cells.

ii. How do the cells you have named in part i. distinguish between self and non-self cells?

From the assessment report:
The cells mentioned in part i. have receptors that are capable of detecting self markers and/or non-self antigens.

[TwinNerd]

Hey guys,
Do you have a condensed and easy to understand summary of transcription and translation? Im so confused right now, and my teacher just quickly skimmed over it and didn't explain it properly. Thanks in advance:)

[biy]

I just got 60/75 for my first practice exam, unit 3 VCAA 2006 exam 1.

How can I work to improve this score? I really want to be losing only a few marks, not a whole 15

My major loss was during the short answer, the multiple choice was only 2 marks lost.

Thanks!

[heids]

Hey guys,
Do you have a condensed and easy to understand summary of transcription and translation? Im so confused right now, and my teacher just quickly skimmed over it and didn't explain it properly. Thanks in advance:)

Transcription (making mRNA by copying the DNA template)
1.  RNA polymerase (the enzyme that controls this process) binds to DNA
2.  DNA unwinds
3.  RNA molecules bind to the DNA template strand by complementary base pairing, so you have an RNA strand complementary to the template strand (called pre-mRNA)
4.  introns (the bits of the gene that don't end up coding for the protein) are cut out and the exons (the coding bits) are stuck together; other stuff happens that I've forgotten and got to research
5.  the mRNA leaves the nucleus and travels to the ribosomes

Translation (turning the genetic code/mRNA template into proteins)
1.  mRNA attaches to ribosome
2.  there's another type of RNA called tRNA.  There's a section on it called an 'anti-codon' - made up of three nucleotide bases.  Each tRNA molecule with a specific anti-codon 'carries' a specific amino acid.
3.  tRNA molecules bind to the mRNA strand - their anticodons bind to triplets of bases mRNA, by complementary base pairing
4.  the amino acids attached to the tRNA molecules join together to make a polypeptide chain

And this is then folded into a protein.

Translation image


Hoping this makes some sense... let me know if it doesn't.  It definitely doesn't cover everything (e.g. start and stop codons, role of RNA polymerase, some of the other things that happen between pre-mRNA and mRNA).

[TheAspiringDoc]

Thank you for that, grannysmith!

Last question, promise ():
How do phagocytes and granulocytes (basically the cells involved in the second line of defence) identify a forgein pathogen, or in other words a non-self cell? Is it fine in VCE bio to just say that the MHC class 1 markers of these cells do not recognise the markers of the pathogens, hence are labelled as non-self? Also are antigens only specific to the third line of defence?


Thank you so much

Never stop asking questions!!

[IndefatigableLover]

I just got 60/75 for my first practice exam, unit 3 VCAA 2006 exam 1.

How can I work to improve this score? I really want to be losing only a few marks, not a whole 15

My major loss was during the short answer, the multiple choice was only 2 marks lost.

Thanks!

This is what I've been doing for my exams (for Biology and Chemistry)!

Categorise your mistakes and write them into a book so that you can refer to later on. You'll find some mistakes you make are just silly ones which aren't really worth putting in but a mental reminder for it is a good thing I suppose. Other mistakes will be more 'conceptual' which I suggest following up with further research to understand how to word your answer correctly (since VCAA answers may be a bit too simple/vague as such). As such, for MCQ, generally I'd log those as well since they are mainly knowledge-based rather than silly mistakes...

Hope that helps

[biy]

Thanks IL! <3

Can someone help me out with protein structure please? This was one of my major loss in the prac exam
How can you define primary structure of proteins? Is it okay to just say that it is the linear sequence of amino acids?
Also secondary structure is the both alpha helices and beta pleated sheets. How do these form? How does a protein go from it's primary structure to the secondary structure?

Thank you!