VCE Biology Question Thread

[-Lilac-]

With question 4c from the 2019 exam, why would the fact that many allergens contribute to an allergic response be relevant here? I say this since flu vaccines incorporate many antigens from different influenza strains, so wouldn't it be possible to make a vaccine that uses many pollen fragments?

This question bugs me for a few reasons (cause there have been and are attempts to develop allergen vaccines) but I would say compared to your standard influenza vaccine with around 4 strains a universal pollen vaccine would have to cover far more allergens.

Edit: As for VCE biology knowledge, wingdings2791's answer covers it well

[Chocolatepistachio]

If someone could help with this question
Which of the following summary statements about vessel resistance is true?
A a direct relationship exists between radius and resistance
B an inverse relationship exists between radius and resistance- as vessel radius decreases resistance decreases x
C as vessel radius increases, there is a concurrent increase in resistance
D proportionally small changes in vessel radius result in relatively large changes in resistance

[darkz]

If someone could help with this question
Which of the following summary statements about vessel resistance is true?
A a direct relationship exists between radius and resistance
B an inverse relationship exists between radius and resistance- as vessel radius decreases resistance decreases x
C as vessel radius increases, there is a concurrent increase in resistance
D proportionally small changes in vessel radius result in relatively large changes in resistance

The relationship between resistance and radius is that as the radius of a vessel is increased, resistance decreases, thereby increasing flow. Conversely, when the radius is decreased, resistance increases, and flow is reduced. If you think about it, a narrower pipe will allow less water to be moved, while a wider pipe will allow more water to be moved. Additionally, the resistance is also inversely proportional to \(radius^4\) - i.e. \(R \propto \frac{1}{r^4}\) and therefore small changes in radius will affect the resistance greatly. (e.g. if we halve the radius (\(\frac{1}{2}^4=\frac{1}{16}\)) we will increase resistance by 16x. If we look at our answer options then:

A - I'm assuming that by direct they mean proportional, where here its inversely proportional? (incorrect)
B - for it to be an inverse relationship, as radius increases, resistance should decrease and vice versa (incorrect)
C - as vessel radius increases, resistance should decrease (incorrect)
D - Yes, as stated above, small changes in radius have large changes in resistance (correct)

[makram]

Question about the antibody tests that are referred to in question 9c of the 2019 VCAA exam.

How exactly does the antibody test work? Do they collect the antibodies and visualise the variable region under a microscope, for example, or is it the process used in ELISA?

[whys]

Question about the antibody tests that are referred to in question 9c of the 2019 VCAA exam.

How exactly does the antibody test work? Do they collect the antibodies and visualise the variable region under a microscope, for example, or is it the process used in ELISA?

I interpreted it to be ELISA, I don’t think they’d visualise the variable region under a microscope - there’d be far more inaccuracy with an antibody test that worked based on what we could see through a microscope I’m sure. However, different antibodies with extremely similar antigen-binding sites may bind to the same antigen, which is what the question wanted us to recognise.

[WhatisaMeMe]

hi quick question is question 1b 2015 short answer part of our 2020 study design? I don't remember learning anything like this.
thanks

[PhoenixxFire]

hi quick question is question 1b 2015 short answer part of our 2020 study design? I don't remember learning anything like this.
thanks

Yeah it is. Lots of confusing info but it's really just asking why piercing the plasma membrane is a problem (ie its testing your understanding of the function of the membrane.)

[WhatisaMeMe]

Yeah it is. Lots of confusing info but it's really just asking why piercing the plasma membrane is a problem (ie its testing your understanding of the function of the membrane.)

thanks pheonixfire for your reply
but I still don't understand because it pierces the membrane, but shouldn't the cell undergo necrosis? not apoptosis?because in the suggested solutions it said u had to write the contents leak out, and then followed by apoptosis. and i dont understand what it meant by 'osmotic gradients disrupted' do you really have to write that to gain full marks?
sorry for my long post i am just confused sorry about that. thanks in advance

[darkz]

thanks pheonixfire for your reply
but I still don't understand because it pierces the membrane, but shouldn't the cell undergo necrosis? not apoptosis?because in the suggested solutions it said u had to write the contents leak out, and then followed by apoptosis. and i dont understand what it meant by 'osmotic gradients disrupted' do you really have to write that to gain full marks?
sorry for my long post i am just confused sorry about that. thanks in advance

For this question, the answers only supply potential solutions to the question, with two ideas being required for the two marks. Because the question is a 'suggest' question, it signifies that they don't actually require you to give the exact pathway, but only a potential (plausible) pathway. If you talked about necrosis, then that would also be sufficient. Likewise, if you stated that it initiated apoptosis, that would also be accepted - both would be acceptable here because the question doesn't require you to know the detail required to differentiate between the pathways here.

The function of the plasma membrane is to separate the intracellular and extracellular environments. Therefore, if you were to pierce the plasma membrane, then the boundary between the intracellular and extracellular environment would no longer exist, allowing for the rapid influx of water (or liquid) into the cell, also changing the concentrations of solutes around the area.

[Sinalih]

Hi, i don't quite understand this question, the answer is supposed to be B.
Thanks

[WhatisaMeMe]

For this question, the answers only supply potential solutions to the question, with two ideas being required for the two marks. Because the question is a 'suggest' question, it signifies that they don't actually require you to give the exact pathway, but only a potential (plausible) pathway. If you talked about necrosis, then that would also be sufficient. Likewise, if you stated that it initiated apoptosis, that would also be accepted - both would be acceptable here because the question doesn't require you to know the detail required to differentiate between the pathways here.

The function of the plasma membrane is to separate the intracellular and extracellular environments. Therefore, if you were to pierce the plasma membrane, then the boundary between the intracellular and extracellular environment would no longer exist, allowing for the rapid influx of water (or liquid) into the cell, also changing the concentrations of solutes around the area.

oooh i understand now thanks alot!!!

[WhatisaMeMe]

Hi, i don't quite understand this question, the answer is supposed to be B.
Thanks

hi for this question, it is best to use cancel out method.
-straight away you can cancel out D because it doesn't make sense because its from simple --> complex and eukaryotes are complex
-A doesnt make sense cuz dinosaurs very complex cannot come before a more simple organism like coral
-C also doesnt make sense because non-flowering plants cant come after insects, insects are quite complex organisms and they have brain so they are more complex
-this leaves us with B which makes sense

[Chocolatepistachio]

For this question would this be a sufficient answer
Explain what happens to enzymes when they become denatured.
If the enzyme is outside the optimal temp of 36.1-37.1 and optimal pH of 7.35- 7.45 it becomes denatured and can no longer function. The active site will change shape and the substrate will no longer be able to fit on the active site.

[homeworkisapotato]

For this question would this be a sufficient answer
Explain what happens to enzymes when they become denatured.
If the enzyme is outside the optimal temp of 36.1-37.1 and optimal pH of 7.35- 7.45 it becomes denatured and can no longer function. The active site will change shape and the substrate will no longer be able to fit on the active site.

You've covered the gist of it but I would probably say:
Denaturation causes the tertiary structure of the enzyme to permanently change shape, changing the shape of the active site, preventing the enzyme from binding to its substrate and functioning. 

I usually don't put the actual values of the temp or pH unless they were given in the problem
Hope this helps!!

[55232Jeremy]

For this question would this be a sufficient answer
Explain what happens to enzymes when they become denatured.
If the enzyme is outside the optimal temp of 36.1-37.1 and optimal pH of 7.35- 7.45 it becomes denatured and can no longer function. The active site will change shape and the substrate will no longer be able to fit on the active site.

Adding to homeworkisapotato, I would also include how denaturation breaks the bonds within the tertiary structure of the protein, such as hydrogen bonds, dispersion forces or disulphide bridges (covalent cross-links).