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May 19, 2021, 03:15:41 am

Author Topic: VCE Biology Question Thread  (Read 2162479 times)  Share 

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specimen

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Re: VCE Biology Question Thread
« Reply #13425 on: April 23, 2021, 06:32:51 pm »
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Hello atarnotes, I recently received my SAC mark for my first SAC and it ended up just above 50 percent. I am still very disappointed with this but I guess I did relatively well because the average was around 38 percent (the SAC was incredibly hard to score well). I dont really understand how the SACs are scaled and stuff but if I was to end up rank 1 would this mean that I get scaled to 100 or the best exam score or something even though I got a garbage score on my SAC? Is it possible to get a bad SAC mark that gives you a high ranking (in comparison to everyone else) and then that equates to something 90+ for your scaled score at the end of the year? my mark is still really disappointing considering the effort i put in and i feel like my study score is going to be screwed bc of this mark and impossible to get above 45.

Sine

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Re: VCE Biology Question Thread
« Reply #13426 on: April 23, 2021, 06:48:30 pm »
+7
Hello atarnotes, I recently received my SAC mark for my first SAC and it ended up just above 50 percent. I am still very disappointed with this but I guess I did relatively well because the average was around 38 percent (the SAC was incredibly hard to score well). I dont really understand how the SACs are scaled and stuff but if I was to end up rank 1 would this mean that I get scaled to 100 or the best exam score or something even though I got a garbage score on my SAC? Is it possible to get a bad SAC mark that gives you a high ranking (in comparison to everyone else) and then that equates to something 90+ for your scaled score at the end of the year? my mark is still really disappointing considering the effort i put in and i feel like my study score is going to be screwed bc of this mark and impossible to get above 45.
Hi, specimen! Welcome to ATAR Notes

Ultimately, your sac rank is what is actually important not what percentage you score. So your 50% may be quite good if the cohort average was only 38%.

Yes, if you are rank 1 that means that your sac scores will be scaled to the standerdised equivalent of the highest exam score that is scored by your cohort. Also yes if your rank is high but your actual score is low it is still possible for your sacs to scale to a 90+ score at the end of the year.

Hope this helps :)


Oynx

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Re: VCE Biology Question Thread
« Reply #13427 on: April 25, 2021, 11:23:20 pm »
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Till what point does a B cell stay naive? and when does it mature?

Thanks
2021 - Biology | Further mathematics

Owlbird83

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Re: VCE Biology Question Thread
« Reply #13428 on: April 26, 2021, 09:46:20 am »
+11
Till what point does a B cell stay naive? and when does it mature?

Thanks
B cells are naive until they encounter an antigen that is complementary to their B cell receptor. The B cell activation occurs when this antigen binds to the naive B cell's receptor and they are stimulated to proliferate and differentiate into B plasma cells and memory B cells.

Naive B cells are considered 'mature'   B cells mature in the bone marrow by going through tests to make sure their receptors are functional (make sure they react to pathogens not self cells).
(Activation is the term used to describe when the naive B cells are exposed to the antigen and proliferate & differentiate.)
« Last Edit: April 26, 2021, 09:51:10 am by Owlbird83 »
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Chocolatepistachio

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Re: VCE Biology Question Thread
« Reply #13429 on: April 27, 2021, 03:20:29 pm »
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Based only on an amino acid sequence how would you recognise an integral membrane protein

PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #13430 on: April 27, 2021, 03:39:54 pm »
+2
Based only on an amino acid sequence how would you recognise an integral membrane protein
You wouldn't. There are some clues (mostly based on whether they're hydrophillic/phobic and how they're folded) but not 100% accuracy and way beyond vce.
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Chocolatepistachio

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Re: VCE Biology Question Thread
« Reply #13431 on: April 27, 2021, 10:20:22 pm »
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Incubation of cells at 20 degrees Celsius blocks the release of proteins from the trans- Golgi. Under such conditions you would expect to see
A an increase in exocytosis of proteins
B a decrease in exocytosis if proteins
C an increase in endocytosis of proteins
D a decrease in endocytosis of proteins

Would this be b

Oynx

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Re: VCE Biology Question Thread
« Reply #13432 on: May 02, 2021, 12:14:44 am »
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Can someone highlight the steps need for the cell-mediated immune response? Just need it for clarification. Thanks
2021 - Biology | Further mathematics

Sine

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Re: VCE Biology Question Thread
« Reply #13433 on: May 02, 2021, 07:33:33 am »
+2
Incubation of cells at 20 degrees Celsius blocks the release of proteins from the trans- Golgi. Under such conditions you would expect to see
A an increase in exocytosis of proteins
B a decrease in exocytosis if proteins
C an increase in endocytosis of proteins
D a decrease in endocytosis of proteins

Would this be b
Yeah, it looks like B is correct. Golgi is used for protein export.

Can someone highlight the steps need for the cell-mediated immune response? Just need it for clarification. Thanks
Which aspect were you unsure of?

Oynx

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Re: VCE Biology Question Thread
« Reply #13434 on: May 02, 2021, 05:32:58 pm »
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Yeah, it looks like B is correct. Golgi is used for protein export.
Which aspect were you unsure of?

just the initiation part, do T helper cells activate the cytotoxic t cells without cytotoxic t cells don't binding to the APC, or do the cytotoxic t cells bind to the APC in order to be activated?
2021 - Biology | Further mathematics

Harrycc3000

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Re: VCE Biology Question Thread
« Reply #13435 on: May 02, 2021, 08:05:05 pm »
+4
just the initiation part, do T helper cells activate the cytotoxic t cells without cytotoxic t cells don't binding to the APC, or do the cytotoxic t cells bind to the APC in order to be activated?
I think for cell mediated immunity its like the naiive T cell (which turns to cytotoxic) binds to any bad antigen (MHC 1 marker) and then gets activated by t helper cell. That means it can be via APC (cross presentation of antigen onto MHC 1 or that APC is just virally infected) but its mostly like bad cells specifically, transplant, cancerous or virally infected cells that will present to the naiive T cell and then an activated T helper cell will later encounter that naiive t cell and then activate it through release of cytokines. What I would say is 'cell mentioned in q stem (it will probably be virally infected) presents antigen on MHC 1 marker to naiive t cell/cytotoxic t cell. Activated T helper cell with specific and complementary receptor to x antigen encounters naiive t cell and activates naiive t cell/cytotoxic t cell via release of cytokines and interleukins.' and then go on with the rest of your response.

What I'm trying to say is that APC is not as defining of a feature in cell mediated immunity as humoral immunity. Humoral immunity APCs are important because those antigens are literally swallowed by them in the fluid (humoral) (MHC 2 markers is taken from endosomal compartments) and so they have to present it to those t helper cells whereas for cytotoxic t cells its more about whether the cell is bad or not (MHC 1 marker more important because it shows what you make) and so those tiny peptides that are engulfed aren't what you care about, what you care about is whether the cell is a bad cell or not. (hence the name cell mediated immunity) and so APCs play less of a role because its less practical to swallow a whole cell and then present it compared to just seeing its MHC 1 marker and straight seeing if its a bad cell or not.

This was a bit of a convoluted confusing explanation sorry about that but hopefully you understand what im trying to say!
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Erutepa

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Re: VCE Biology Question Thread
« Reply #13436 on: May 02, 2021, 10:16:18 pm »
+5
just the initiation part, do T helper cells activate the cytotoxic t cells without cytotoxic t cells don't binding to the APC, or do the cytotoxic t cells bind to the APC in order to be activated?
In activation of naive cytotoxic t cells, the APC will bind both the helper t cell and a naive cytotixic t cell specific to that antigen. This cytotoxic t cell will receive stimulation from both the APC and the helper t cell resulting in its clonal selection and subsequent differentiation and proliferation. These activated cytotoxic t cells will then travel throughout the host where they will bind to MHC class I molecules presenting their specific antigen, and initiate the death of these cells through release of perforin to create a pore in the target cell and granzymes which enter through the pore and trigger apoptosis (intrinsic pathway).
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Chocolatepistachio

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Re: VCE Biology Question Thread
« Reply #13437 on: May 03, 2021, 10:24:20 pm »
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What exactly is the purpose of the introns

-Lilac-

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Re: VCE Biology Question Thread
« Reply #13438 on: May 04, 2021, 10:07:54 am »
+8
What I would say is 'cell mentioned in q stem (it will probably be virally infected) presents antigen on MHC 1 marker to naiive t cell/cytotoxic t cell. Activated T helper cell with specific and complementary receptor to x antigen encounters naiive t cell and activates naiive t cell/cytotoxic t cell via release of cytokines and interleukins.' and then go on with the rest of your response.

What I'm trying to say is that APC is not as defining of a feature in cell mediated immunity as humoral immunity.

While this is probably okay for VCE biology,  I would be cautious about saying APCs are not a fundamental part of cell-mediated immunity. The following stuff is outside the VCE course, but we know that dendritic cells (DC) are really the only cell capable of activating T cells as they have the correct co-stimulatory molecules. Thus, for a T helper or a cytotoxic T cell to be activated, they usually require antigen presentation by a DC (via cross-presentation for MHC I if DC is not infected itself) to be activated (but this is biology and there are always exceptions haha). If a T cell just binds antigen without any co-stimulation it is programmed to die via apoptosis.

So for T helper or cytotoxic T cell to be activated, it does require APCs. And once a T helper is activated it can then help activate a Cytotoxic T cell that is also bound to a DC (sometimes the DC alone does not provide enough activating stimulation and needs 'help').
It is thought that the T helper binds to the DC itself to help further activate the DC which can then better activate the cytotoxic T cell (td;lr immunology is really complex haha so don't worry if this isn't making much sense)!

Importantly, once activated, by usually both an APC and T helper, the cytotoxic T cell can then assert its effector function on a cell presenting the correct antigen on MHC I.

In activation of naive cytotoxic t cells, the APC will bind both the helper t cell and a naive cytotixic t cell specific to that antigen. This cytotoxic t cell will receive stimulation from both the APC and the helper t cell resulting in its clonal selection and subsequent differentiation and proliferation. These activated cytotoxic t cells will then travel throughout the host where they will bind to MHC class I molecules presenting their specific antigen, and initiate the death of these cells through the release of perforin to create a pore in the target cell and granzymes which enter through the pore and trigger apoptosis (intrinsic pathway).

This is a good description for VCE biology. Don't talk about all that dendritic cells stuff I just described! That was just a bit of extra info.

What exactly is the purpose of the introns

While they don't code for the protein they are important for gene regulation. They can also code for things called functional RNAs (not VCE info).
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Chocolatepistachio

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Re: VCE Biology Question Thread
« Reply #13439 on: May 04, 2021, 01:46:37 pm »
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The rough endoplasmic reticulum also makes the membranes for organelles that are not in the endomembrane system however the membrane components are transferred to these organelles in other ways.

How are the membrane components transferred to these organelles?