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October 30, 2020, 05:35:04 pm

Author Topic: VCE Biology Question Thread  (Read 1853896 times)  Share 

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Coolgalbornin03Lo

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Re: VCE Biology Question Thread
« Reply #12975 on: September 20, 2020, 08:04:33 pm »
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I’ve always understood B cells are for extra cellular pathogens and T cells are for intracellular pathogens is this incorrect?

In the solutions my teacher made for a question asking how b and T cells work together an explanation is B cells are for extracellular environment whereas T cells are for intracellular environment.

Also so Naive T cells exist? Or are they cytotoxic T cells? I always thought it was T cells which proliferate and differentiate into T memory cells and Cytotoxic T cells but now I’m not quite sure :(
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-Lilac-

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Re: VCE Biology Question Thread
« Reply #12976 on: September 20, 2020, 08:27:00 pm »
+3
I’ve always understood B cells are for extra cellular pathogens and T cells are for intracellular pathogens is this incorrect?

In the solutions my teacher made for a question asking how b and T cells work together an explanation is B cells are for extracellular environment whereas T cells are for intracellular environment.

CD8 T cells (cytotoxic T cells) can kill infected cells, so they do play an important role in the response against intracellular pathogens. However, B cells do as well as they can produce neutralizing antibodies that prevent the virus from being able to infect a cell. Think about vaccines, very few induce a T cell response but rather are aiming to produce neutralizing antibodies against the virus/bacteria.     

Helper T cells are also very important in intracellular and extracellular pathogen responses. There are subtypes of Th cells that direct intracellular or extracellular responses (don't worry about this but I am just showing you how they have roles in both types of infections). For example, helper T cells are important for activating B cells to produce antibodies in extracellular (and intracellular) infections.

So overall, I see helper T cells and B cells as being involved in both types of infections. However, cytotoxic T cells are not very useful in extracellular pathogen response. I would discuss this further with your teacher to maybe understand what they meant by B cells = extracellular and T cells = intracellular.

It could have been an oversimplification (or maybe VCE knowledge-wise it is ok?- someone here may be able to comment on that I am not very up to date with the study design).

EDIT: As SmartWorker has pointed out what your teacher says seems to be consistent with VCE knowledge. I may have gone into a bit too much detail, so sorry & just ignore if it confuses you!

Also so Naive T cells exist? Or are they cytotoxic T cells? I always thought it was T cells which proliferate and differentiate into T memory cells and Cytotoxic T cells but now I’m not quite sure :(

Naive T cells are T cells that have never seen their antigen before and live in the lymph nodes/secondary lymph tissue. They can be CD8 or CD4 cells. When they are presented their antigen they will proliferate into effector T cells (either CD8 or CD4) or memory cells and be allowed to travel to the site of infection.
« Last Edit: September 20, 2020, 09:30:08 pm by -Lilac- »
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Chocolatepistachio

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Re: VCE Biology Question Thread
« Reply #12977 on: September 20, 2020, 08:47:08 pm »
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Initially studied as an agent of disease in plants, it is small enough to pass through a porcelain filter. Attempts to culture it in a nutrient-rich medium failed, and it could not be seen with a light microscope. It was also discovered that this agent of disease could only be cultured in living cells; the cells then produced copies of this agent.

You identified and classified this as an agent of disease- virus
Which of the following statements best support you answer
A the agent has organelles
B it is an agent of disease in plants
C the agent has nucleic acid
D the agent is not a cell it does not have cytoplasm
E the agent is small it cannot be seen with the light microscope
F the agent requires living host cells to reproduce

Which would be the correct answers  Why not b or c or e

SmartWorker

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Re: VCE Biology Question Thread
« Reply #12978 on: September 20, 2020, 09:10:30 pm »
+6

Initially studied as an agent of disease in plants, it is small enough to pass through a porcelain filter. Attempts to culture it in a nutrient-rich medium failed, and it could not be seen with a light microscope. It was also discovered that this agent of disease could only be cultured in living cells; the cells then produced copies of this agent.

You identified and classified this as an agent of disease- virus
Which of the following statements best support you answer
A the agent has organelles
B it is an agent of disease in plants
C the agent has nucleic acid
D the agent is not a cell it does not have cytoplasm
E the agent is small it cannot be seen with the light microscope
F the agent requires living host cells to reproduce

Which would be the correct answers  Why not b or c or e

It is asking you for the best answer not all correct answers.
So, .: D and F is correct.

A is wrong: viruses do not have organelles
B is wrong: but already mentioned in stem. For example if you have a bacteria, fungi and virus all 3 may be agents of disease in plants:  you cannot differentiate using this.
C is wrong: bacteria have nucleic acids, so doesn't narrow it down to viruses.
D: correct. Viruses need a cytoplasm to replicate---> .: there are obligate intracellular pathogens
E: Light microscopes are limited. hence other pathogens other than viruses cannot be see using Light microscope.
F is correct


-snip-

For VCE:
T cells ---> involved in destroying infected cells or 'presented' antigens i.e: when cells infected they present pathogenic antigens. (I think intracellular environment in the question relates to inside cells)
B cells --> involved directly with free-moving pathogens or 'raw' antigens (I think extracellular environment refers to outside cells)
« Last Edit: September 20, 2020, 09:19:22 pm by SmartWorker »
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Chocolatepistachio

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Re: VCE Biology Question Thread
« Reply #12979 on: September 20, 2020, 09:51:41 pm »
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Thanks!

What does prokaryotes that live in a colonial form mean 


homeworkisapotato

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Re: VCE Biology Question Thread
« Reply #12980 on: September 21, 2020, 07:54:26 am »
+5
Thanks!

What does prokaryotes that live in a colonial form mean
They live in big groups together clustered in one spot. For example, on an agar plate you would see bacteria growing in fuzzy little circles, and those circles you would refer to as colonies.
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Bri MT

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Re: VCE Biology Question Thread
« Reply #12981 on: September 21, 2020, 01:09:01 pm »
+5
thanks

i'm not sure how to answer this question
why do you think the hawk, although a descendent of the most recent common ancestor, is not included in the dinosaur group

 

This is more of a description than a way you would need to answer it but here are some thoughts:

It's fairly common for people to group things in paraphyletic categories (i.e. not include all descendants of a common ancestor together) e.g. people don't consider birds reptiles. In the past, morphology based classification was pretty common & this is still informally used frequently. Additionally with dinosaurs you have the consideration that people tend to think of those as existing on a particular temporal scale (in the past, not as extant species)

Chocolatepistachio

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Re: VCE Biology Question Thread
« Reply #12982 on: September 21, 2020, 04:52:12 pm »
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why are protista paraphyletic whereas the other kingdoms are monophyletic

Bri MT

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Re: VCE Biology Question Thread
« Reply #12983 on: September 21, 2020, 06:47:24 pm »
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why are protista paraphyletic whereas the other kingdoms are monophyletic

I'm not really sure what your question is but protists are basically an "other" group which captures a bunch of eukaryotes. Are you asking about the history of the term?

Chocolatepistachio

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Re: VCE Biology Question Thread
« Reply #12984 on: September 21, 2020, 07:02:01 pm »
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Ah no

I was wondering why protista group would be considered paraphyletic whereas fungi, Animalia and plantae are monophyletic

homeworkisapotato

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Re: VCE Biology Question Thread
« Reply #12985 on: September 21, 2020, 08:22:01 pm »
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Ah no

I was wondering why protista group would be considered paraphyletic whereas fungi, Animalia and plantae are monophyletic
It's because scientists believe that protists do not share a common ancestor with animalia and plantae.
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Re: VCE Biology Question Thread
« Reply #12986 on: September 22, 2020, 09:36:28 am »
+2
Ah no

I was wondering why protista group would be considered paraphyletic whereas fungi, Animalia and plantae are monophyletic

It's because scientists believe that protists do not share a common ancestor with animalia and plantae.

You're thinking along the right lines but not quite there. Something being paraphyletic doesn't mean there isn't a shared common ancestor, it means you're talking about a group which doesn't include all of the descendants of the most recent shared common ancestor.

refortyp

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Re: VCE Biology Question Thread
« Reply #12987 on: September 22, 2020, 02:32:44 pm »
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Do we need to know about gene therapy for the 2020 exam? I've been doing a few of the past exams and they've mentioned it, and I'm not sure whether we need to know something specific for it, or whether it's just the idea of using DNA technology to change faulty genes?

Thanks!

Coolgalbornin03Lo

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Re: VCE Biology Question Thread
« Reply #12988 on: September 22, 2020, 07:54:00 pm »
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Do we need to know about gene therapy for the 2020 exam? I've been doing a few of the past exams and they've mentioned it, and I'm not sure whether we need to know something specific for it, or whether it's just the idea of using DNA technology to change faulty genes?

Thanks!

I think we just need to know a few examples of social, biological and ethical implications- at least that’s all I learnt in class :)

I have a question from the 2012 Bio Exam 1. The question asks why pig insulin could be used to replace human insulin. I answered “the sequence of amino acids at 8,9,10 is that same as in humans so would code for the same protein which gives the polypeptide the same properties as the human insulin proteins”

However vcaa answered that the “shape/structure should be most similar to the human insulin” should I give myself 1 mark, 2 marks or none??
I’m leaning towards no marks as I said same amino acids at 8,9,10 instead of “amino acid of alpha chain” like they said.
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darkz

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Re: VCE Biology Question Thread
« Reply #12989 on: September 22, 2020, 08:07:53 pm »
+5
I think we just need to know a few examples of social, biological and ethical implications- at least that’s all I learnt in class :)

I have a question from the 2012 Bio Exam 1. The question asks why pig insulin could be used to replace human insulin. I answered “the sequence of amino acids at 8,9,10 is that same as in humans so would code for the same protein which gives the polypeptide the same properties as the human insulin proteins”

However vcaa answered that the “shape/structure should be most similar to the human insulin” should I give myself 1 mark, 2 marks or none??
I’m leaning towards no marks as I said same amino acids at 8,9,10 instead of “amino acid of alpha chain” like they said.

In my opinion, saying 8,9,10 instead of alpha chain is not a problem - you're still identifying the similarity which is the idea of the question. The only problem I'd have with your answer is that you say it would code for the same 'protein', which isn't entirely true since the beta chain isn't the same. It would've been better to say they it codes for the same amino acids in relation to the 8,9,10 (or alpha), which in turn causes etc. So I'd probably just give it 1mk.
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