VCE Biology Question Thread

[Scribe]

Hey guys,

Do we need to know about specific plant hormones such as auxins? What level of detail should we know?
Also, do we need to know about pathogens such as prions, viruses, arthropods, hydatid? What level of detail should we know?

Thanks!

[darkz]

Hey guys,

Do we need to know about specific plant hormones such as auxins? What level of detail should we know?
Also, do we need to know about pathogens such as prions, viruses, arthropods, hydatid? What level of detail should we know?

Thanks!

For plant hormones, you should have a general idea of each one does - you don't need to know them in a lot of depth. As for the pathogens, you should know bacteria, viruses and prions quite well - structure, function, etc. I don't really think you need to know arthropods, hydatid to much extent

[vox nihili]

Hey guys,

Do we need to know about specific plant hormones such as auxins? What level of detail should we know?
Also, do we need to know about pathogens such as prions, viruses, arthropods, hydatid? What level of detail should we know?

Thanks!

For plant hormones, you should have a general idea of each one does - you don't need to know them in a lot of depth. As for the pathogens, you should know bacteria, viruses and prions quite well - structure, function, etc. I don't really think you need to know arthropods, hydatid to much extent

Prions probably aren't that important tbh. One could make the argument that even the little attention they get in VCE is too much given how rare prion diseases are.
Add fungi to the list as well, should know a bit about them!

[Scribe]

For plant hormones, you should have a general idea of each one does - you don't need to know them in a lot of depth. As for the pathogens, you should know bacteria, viruses and prions quite well - structure, function, etc. I don't really think you need to know arthropods, hydatid to much extent

Prions probably aren't that important tbh. One could make the argument that even the little attention they get in VCE is too much given how rare prion diseases are.
Add fungi to the list as well, should know a bit about them!

Thanks for the quick response. Another short one: Do we need to understand phototropism?

Cheers!

[darkz]

Thanks for the quick response. Another short one: Do we need to understand phototropism?

Cheers!

Phototrophism was taken out of the study design, so you don't need to know it

[Erutepa]

Phototrophism was taken out of the study design, so you don't need to know it

Is this the same for other tropisms like geotropism (or gravotropsim) and what not.
I am really not as aquinted with the study design as I should be.

[darkz]

Is this the same for other tropisms like geotropism (or gravotropsim) and what not.
I am really not as aquinted with the study design as I should be.

Yup, thats correct

[Erutepa]

Yup, thats correct

Thanks

[PopcornTime]

How does increasing the concentration of auxin past the optimum cause a decrease in shoot/root length?

Is it due to denaturation of receptors?

[darkz]

How does increasing the concentration of auxin past the optimum cause a decrease in shoot/root length?

Is it due to denaturation of receptors?

Don't think you need to know this, but auxins actually pump hydrogen ions into the cell wall, lowering the pH inside so that enzymes, with a lower optimum pH can break the cross bridges between cellulose fibers => turgor pressure and then cell expansion. So I'd assume that if the auxin concentration is past the optimum, that causes the pH to decrease (more H+, making it more acidic) below the optimum pH of the enzymes which break the cross fibers, therefore inhibiting growth

[vox nihili]

Don't think you need to know this, but auxins actually pump hydrogen ions into the cell wall, lowering the pH inside so that enzymes, with a lower optimum pH can break the cross bridges between cellulose fibers => turgor pressure and then cell expansion. So I'd assume that if the auxin concentration is past the optimum, that causes the pH to decrease (more H+, making it more acidic) below the optimum pH of the enzymes which break the cross fibers, therefore inhibiting growth

Awesome knowledge, but agreed that it's beyond the course. So if you're reading this and shat yourself, dw dw

I didn't know any of this though, that's really cool!

[DreamThatBecameADream]

Okay, i have a few questions:
1: Do macrophhages present antigens on MHC 2 or the MHC 1?
2: How do phagocytes actually recognise pathogens? They don't have antibodies or anything so how do they recognise? Is it their MHC 2 ?
3: I had a question asking to identify a cell that acts as a "receptor" for a particular bacteria, so i said thhe T helper cell is thhat correct?
4: after that question, there was another question asking to explain another way that bacteria could be recognised FROM other cells, this confused me, i imagined it would be how T helper cell (that i gave previously) would recognise the bacteria through another cell, such as a macrophage presenting the bacteria's antigen. Would that be right? I was gonna write how a different cell would recognise the bacteria, such as how a B cell will hhave it's antibody bind to the antigen, but i didnt do that because the question said "From other cells" not "by other cells"
I dont know, it confused me a lot.

[PhoenixxFire]

1: Do macrophhages present antigens on MHC 2 or the MHC 1?

They present antigens from the pathogens they engulf on MHC2. They present antigens that are produced in their own cell on MHC1 (like all nucleated cells do)

2: How do phagocytes actually recognise pathogens? They don't have antibodies or anything so how do they recognise? Is it their MHC 2 ?

This is beyond VCE, and I don't know much about it myself. There are some things (like complement proteins) that help them recognise pathogens though.

3: I had a question asking to identify a cell that acts as a "receptor" for a particular bacteria, so i said thhe T helper cell is thhat correct?
4: after that question, there was another question asking to explain another way that bacteria could be recognised FROM other cells, this confused me, i imagined it would be how T helper cell (that i gave previously) would recognise the bacteria through another cell, such as a macrophage presenting the bacteria's antigen. Would that be right? I was gonna write how a different cell would recognise the bacteria, such as how a B cell will hhave it's antibody bind to the antigen, but i didnt do that because the question said "From other cells" not "by other cells"
I dont know, it confused me a lot.

Maybe it wanted you to answer it the other way around? Like B cells act as a receptor and then T helper cells recognise bacteria from other cells (macrophages, dendritic cells). It's a bit hard to tell without the exact wording of the question.

[vox nihili]

Okay, i have a few questions:
1: Do macrophhages present antigens on MHC 2 or the MHC 1?
2: How do phagocytes actually recognise pathogens? They don't have antibodies or anything so how do they recognise? Is it their MHC 2 ?
3: I had a question asking to identify a cell that acts as a "receptor" for a particular bacteria, so i said thhe T helper cell is thhat correct?
4: after that question, there was another question asking to explain another way that bacteria could be recognised FROM other cells, this confused me, i imagined it would be how T helper cell (that i gave previously) would recognise the bacteria through another cell, such as a macrophage presenting the bacteria's antigen. Would that be right? I was gonna write how a different cell would recognise the bacteria, such as how a B cell will hhave it's antibody bind to the antigen, but i didnt do that because the question said "From other cells" not "by other cells"
I dont know, it confused me a lot.

PF (as usual) has given really good answers here, so I won't labour any of the points.

Question two though was a sticking point. It's probably outside of the course (although 2/3 of the new Biology textbooks talk about this). Phagocytes have a special class of receptors on their surface called PRRs (pathogen recognition receptors). These receptors can respond to a class of molecules called PAMPs (pathogen associated molecular patterns). Basically PAMPs are a small group of molecules that pathogens have, but human cells do not have. A good example of this is the molecule lipopolysaccharide, which is a component of the bacterial cell wall. As human cells don't have cell walls, we don't have lipopolysaccharide. So it makes sense then that this would be a good molecule for phagocytes to respond to, as it can't occur on human cells but does occur on bacteria; meaning that the phagocyte will respond to the bacterium whilst ignoring self cells

[DreamThatBecameADream]

The exact question was "Explain how salmonella would be recognised from other cells"
I think you're right, PF, that it would be other way around. i should have spoken about B cells, but i was just stupid enough to think that the wording would be "by other cells" rather than "from other cells"
That's my problem, i overthink the way questions are worded. that's usually where i lose marks