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December 13, 2019, 09:00:17 pm

Author Topic: VCE Biology Question Thread  (Read 1454826 times)  Share 

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Genshai

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Re: VCE Biology Question Thread
« Reply #12090 on: October 19, 2019, 09:03:12 pm »
0
Hello,
i have a question (or two?) about apoptosis :)
Is it the cell that undergoes apoptosis the one that signals for phagocytes? and is this with cytokines?
- thank you in advance !!!
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BitcoinEagle

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Re: VCE Biology Question Thread
« Reply #12091 on: October 19, 2019, 09:08:12 pm »
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Hello everyone,
I've just attempted the QAT VCE Biology written examination from 2018. I had some multiple-choice questions that I wasn't sure of. Could you guys have a look and let me know whether there is a problem in the actual test?

Production of mRNA would begin at the region of the DNA starting at the:
a) operon
b) DNA polymerase binding site
c) promoter region
d) Start codon

D is said to be the right answer although I thought at a DNA strand does not have codons? Is this a mistake in the test?

Another question is this one:

Which statement with regards to enzyme inhibition is correct?
a) Poisons can be irreversible competitive inhibitors
b) Non-competitive inhibition is permanent
c) All competitive inhibition is reversible.
d) Non-competitive inhibits bind to the active site.

Is this something that we need to know for the exam? I thought that the answer was b as this leads to a permanent change in the tertiary structure of an enzyme and hence permanently changes it's function.

Finally, I found this one a bit vague:

What process allows the comparison of DNA of different species to be made?
a) Comparative anatomy
b) DNA-DNA hybridization
c) Polymerase Chain reaction
d) Molecular Clock

I answered D, but the answer is said to be B. Would both answers work?

Thanks everyone.
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BitcoinEagle

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Re: VCE Biology Question Thread
« Reply #12092 on: October 19, 2019, 09:11:39 pm »
+1
Hello,
i have a question (or two?) about apoptosis :)
Is it the cell that undergoes apoptosis the one that signals for phagocytes? and is this with cytokines?
- thank you in advance !!!

Yes, from what I know, apoptosis undergoes the following stages:
Caspases are activated.
Cleaving of proteins and DNA.
Destruction of mitochondria.
Blebbing of contents.
Forming of apoptotic bodies.
Secretion of cytokines to attract phagocytes.

This is done by the cell and with cytokines (which are signaling molecules within the immune system)
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Re: VCE Biology Question Thread
« Reply #12093 on: October 19, 2019, 09:28:34 pm »
+11
4(a) seems to be relevant to the study design, although some of their (many) suggested answers dont include information we need to know now. Your answer seems to fit within their suggested answer "comparison of chromosomes (or genetic information) between parents and offspring". Obviously you need 2 more points to get 3 marks but that would be worth 1.
Although none of the information in those suggested answers is directly in the study design, it could come under the part of experimental design about controlled variables and you could still get questions that expect you to come up with that type of answer.

8d
I wrote that they had conflict and had competition between them for resources such as food. Is this a valid point? Would I get a mark for this?
That isn't a reason for interbreeding to not occur. You need to talk about a type of reproductive isolation (they are in the same location at the same time so that's the type of isolation that must be occuring).

Hi, I have a question.
How can interbreeding occur amongst different early human species like the Denisovans/Neanderthals and modern humans if species are not meant to be able to interbreed? Because in allopatric speciation, when different species meet after being separated, they cannot produce fertile , viable offspring
The short answer is that our definition of a species isn't perfect. Although we call them different species, they don't really meet the criteria for it.

Because speciation isnt an instant process, often times that definition can be a little blurry or confusing when talking about instances like that. Whilst if we compare modern homo sapiens to homo denisovans or neanderthalensis, we are different species
But if ancient homo sapiens could interbreed with denisovans and neanderthals, and modern homo sapiens can't, then are modern and ancient homo sapiens really the same species? (Biology is complicated and doesn't have clear divisions haha)

Hello,
i have a question (or two?) about apoptosis :)
Is it the cell that undergoes apoptosis the one that signals for phagocytes? and is this with cytokines?
- thank you in advance !!!
There are a lot of different things that signal for phagocytes depending on why the cell is undergoing apoptosis, but yes the cell will do it too. Cytokines is very non-specific. It's not really any different than saying "immune signals" but don't worry about it, you don't need to know the specifics.

Hello everyone,
I've just attempted the QAT VCE Biology written examination from 2018. I had some multiple-choice questions that I wasn't sure of. Could you guys have a look and let me know whether there is a problem in the actual test?

Production of mRNA would begin at the region of the DNA starting at the:
a) operon
b) DNA polymerase binding site
c) promoter region
d) Start codon

D is said to be the right answer although I thought at a DNA strand does not have codons? Is this a mistake in the test?
Yeah, that answer would be correct for the production of a polypeptide chain, not for mRNA.

Another question is this one:

Which statement with regards to enzyme inhibition is correct?
a) Poisons can be irreversible competitive inhibitors
b) Non-competitive inhibition is permanent
c) All competitive inhibition is reversible.
d) Non-competitive inhibits bind to the active site.

Is this something that we need to know for the exam? I thought that the answer was b as this leads to a permanent change in the tertiary structure of an enzyme and hence permanently changes it's function.
A is the correct answer, but this is an unreasonable question. You're not specifically taught about poisons in VCE, and you are taught that non-competitive inhibition is permanent (this isn't actually true).

Finally, I found this one a bit vague:

What process allows the comparison of DNA of different species to be made?
a) Comparative anatomy
b) DNA-DNA hybridization
c) Polymerase Chain reaction
d) Molecular Clock

I answered D, but the answer is said to be B. Would both answers work?

Thanks everyone.
The molecular clock just refers to the standard rate of mutation. You can use this to approximate how long ago species diverged from a common ancestor but it is not a method of comparing the DNA of species.
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BitcoinEagle

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Re: VCE Biology Question Thread
« Reply #12094 on: October 19, 2019, 09:41:49 pm »
0
Although none of the information in those suggested answers is directly in the study design, it could come under the part of experimental design about controlled variables and you could still get questions that expect you to come up with that type of answer.
That isn't a reason for interbreeding to not occur. You need to talk about a type of reproductive isolation (they are in the same location at the same time so that's the type of isolation that must be occuring).

The short answer is that our definition of a species isn't perfect. Although we call them different species, they don't really meet the criteria for it.

But if ancient homo sapiens could interbreed with denisovans and neanderthals, and modern homo sapiens can't, then are modern and ancient homo sapiens really the same species? (Biology is complicated and doesn't have clear divisions haha)

There are a lot of different things that signal for phagocytes depending on why the cell is undergoing apoptosis, but yes the cell will do it too. Cytokines is very non-specific. It's not really any different than saying "immune signals" but don't worry about it, you don't need to know the specifics.

Yeah, that answer would be correct for the production of a polypeptide chain, not for mRNA.
A is the correct answer, but this is an unreasonable question. You're not specifically taught about poisons in VCE, and you are taught that non-competitive inhibition is permanent (this isn't actually true).
The molecular clock just refers to the standard rate of mutation. You can use this to approximate how long ago species diverged from a common ancestor but it is not a method of comparing the DNA of species.

Brilliant! This makes so much sense, thanks PhoenixxFire!
 :)
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Re: VCE Biology Question Thread
« Reply #12095 on: October 19, 2019, 11:35:19 pm »
0
Hello,
Does anyone have any advice on what to do in the coming days leading up to the exam? I have done all the past papers I have access to and I'm feeling a little at loss with what to do now... Thanks in advance!

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Re: VCE Biology Question Thread
« Reply #12096 on: October 20, 2019, 07:10:00 am »
+4
Hello,
Does anyone have any advice on what to do in the coming days leading up to the exam? I have done all the past papers I have access to and I'm feeling a little at loss with what to do now... Thanks in advance!
1. Make sure you've harshly marked you're past exams, or got a teacher to do it. You're not going to gain anything from going easy on yourself.
2. Make sure you've gone through all the exams you've done and understand what you got wrong and how you got it wrong. If there's weaker areas in you're knowledge that you keep getting questions wrong about, you might want to make some summary notes or draw a diagram or something else that helps you revise that content.
3. I would then make sure you actually redo any questions you've got wrong. It's easy to read the answer sheet and tell yourself that you'll remember the correct response for next time, but I think it's far better to be rewriting and questions answered incorrectly.
4.do more practices exams. You may have done all the past vcaa ones, but I'm sure you're teacher has company exams that you could ask for.

Hope this helps, and good luck with biology.
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Evolio

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Re: VCE Biology Question Thread
« Reply #12097 on: October 20, 2019, 09:35:13 am »
0
Quote
You need to talk about a type of reproductive isolation (they are in the same location at the same time so that's the type of isolation that must be occuring).
I don't understand this part. Could you please clarify? What do you suggest when answering this question? I still don't understand why competition wouldn't be a reason for interbreeding not to occur.

« Last Edit: October 20, 2019, 09:38:25 am by Evolio »
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Re: VCE Biology Question Thread
« Reply #12098 on: October 20, 2019, 10:09:25 am »
+4
I don't understand this part. Could you please clarify? What do you suggest when answering this question? I still don't understand why competition wouldn't be a reason for interbreeding not to occur.

With reproductive isolation the individuals cannot naturally mate. This may be behavioural, for example they are too phenotypically different so refuse to mate with each other or it may be physically impossible because genitalia might not be compatible which is the case for many species of flys. Even though they can't naturally produce offspring, through human intervention this may be possible. 

I hope this answers part of your question!

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Re: VCE Biology Question Thread
« Reply #12099 on: October 20, 2019, 10:18:05 am »
+4
I don't understand this part. Could you please clarify? What do you suggest when answering this question? I still don't understand why competition wouldn't be a reason for interbreeding not to occur.



You're thinking on an individual level whereas you should be thinking on a subpopulation level.

Competition for resources would not result in two subpopulations becoming distinct,  it would result in traits giving a competitive advantage becoming more common in subsequent generations (assuming a bunch of conditions are met)

 In just about every population the number of organisms which produce fertile offspring in each generation is less than the number of organisms in that generation (remember competition to survive & reproduce as a component  of evolution by natural selection?). If you have a population that's changing allele frequencies that's evolution but this does not mean that speciation is occurring.

For speciation you need to have groups that are having their allele frequencies become more different over generations.  Thus, you need some sort of barrier to gene flow between the groups so they don't keep making each other more similar. Competition might prevent some individuals from breeding but it doesn't prevent populations from breeding.
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Re: VCE Biology Question Thread
« Reply #12100 on: October 20, 2019, 12:18:55 pm »
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Why do allergic responses get worse upon second and third exposures?

I wrote that it is because of pre existing memory cells from the first response, which induces a greater and faster response upon which more Ig E antibodies are produced and prime mast cells by binding to their surface receptors, such that upon reexposure more mast cells are activated via crosslinkage with the allergen and more histamine is released, causing heightened inflammation.

I find it a weird answer though, because it doesnít really mention why itís worse upon the second exposure, and itís moreso about the third and future exposures to the allergen. Can someone check over it?
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BitcoinEagle

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Re: VCE Biology Question Thread
« Reply #12101 on: October 20, 2019, 05:35:29 pm »
+2
Why do allergic responses get worse upon second and third exposures?

I wrote that it is because of pre existing memory cells from the first response, which induces a greater and faster response upon which more Ig E antibodies are produced and prime mast cells by binding to their surface receptors, such that upon reexposure more mast cells are activated via crosslinkage with the allergen and more histamine is released, causing heightened inflammation.

I find it a weird answer though, because it doesnít really mention why itís worse upon the second exposure, and itís moreso about the third and future exposures to the allergen. Can someone check over it?

This is a pretty good answer. The reason that second and third responses are successively more extreme, is simply because, in each successive response, more antibodies are created which bind to more mast cells. Hence, when the body is reexposed to the antigen, each successive time, more histamine is released and hence the inflammation symptoms including constriction of airways, reddening and swelling etc increase. This can be dangerous if the levels of histamine are high enough.

To everyone else:
In STAV 2018, Q5:

Transcription in:
a) Eukaryotic cells differ from that in prokaryotic cells as eukaryotic cells do not have promoters like eukaryotic cells.
b)Eukaryotic cells differ from that in prokaryotic cells as eukaryotic cells require transcription factors to bind to a promoter region whereas prokaryote cells do not
C) Both eukaryotic cells and prokaryotic cells occur in the cytosol of the cell.
D) Both eukaryotic and prokaryotic cells involve modification of the transcribed RNA.

How is the correct answer discerned here?
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Re: VCE Biology Question Thread
« Reply #12102 on: October 20, 2019, 05:43:25 pm »
+3
Transcription in:
a) Eukaryotic cells differ from that in prokaryotic cells as eukaryotic cells do not have promoters like prokaryotic cells.
b)Eukaryotic cells differ from that in prokaryotic cells as eukaryotic cells require transcription factors to bind to a promoter region whereas prokaryote cells do not
C) Both eukaryotic cells and prokaryotic cells occur in the cytosol of the cell.
D) Both eukaryotic and prokaryotic cells involve modification of the transcribed RNA.

A: Eukaryotes have promoters
C: Transcription occurs in the nucleus for Eukaryotic
D: Prokaryotes don't have post-transcriptional factors

That leaves B.
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Re: VCE Biology Question Thread
« Reply #12103 on: October 20, 2019, 10:12:04 pm »
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this is a reallyy simple question but the answer to this question in a prac exam is tripping me up so i'm wondering if someone can please clarify it for me

i'm pretty sure that channel proteins are involved in facilitated diffusion only, right?


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Re: VCE Biology Question Thread
« Reply #12104 on: October 21, 2019, 07:11:24 am »
+2
this is a reallyy simple question but the answer to this question in a prac exam is tripping me up so i'm wondering if someone can please clarify it for me

i'm pretty sure that channel proteins are involved in facilitated diffusion only, right?
Protein channels are involved in facilitated diffusion, but I'm 99% sure that they're also involved in active transport. ;D
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