VCE Biology Question Thread

[eagles]

For Insight exam 2010 Unit 3 MCQ 9, there is a statement above the graph stating,
"The graph shows the progress of an endergonic reaction with and without an enzyme."
The general shape of the graph is attached below, and I was wondering whether it was meant to say exergonic instead of endergonic?

Thank you.

[Scooby]

For Insight exam 2010 Unit 3 MCQ 9, there is a statement above the graph stating,
"The graph shows the progress of an endergonic reaction with and without an enzyme."
The general shape of the graph is attached below, and I was wondering whether it was meant to say exergonic instead of endergonic?

Thank you.

Yeah, should be exergonic

[Frozone]

Could someone please help me with these question?(the ones circled)

[Reus]

Could someone please help me with these question?(the ones circled)

for e)
Higher CO2 levels will boost plant growth and food production. Hence why it is essential.
Also relating to your data, CO2 makes sure O2 isn't broken down.

[nhmn0301]

Could someone please help me with these question?(the ones circled)

For c) (i.e the picture) since I cannot fully see it in the photo so I'm assuming they are talking about the light dependent stage which happens in the thylakoid membrane.
Some chemical changes are: ADP + Pi -> ATP, NADP+ -> NADPH, water is split to donate its electrons to the chlorophyll.
d) Thats the compensation point where the level of CO2 = O2.
It starts to flatten because the RuBisCo enzyme which involves in the carbon fixation process is getting saturated so the rate of photosynthesis just remains around that point.
e) I think that's question is a given.... H2O2 and NH3 is considered to be toxic (to both animal and plant, thats why human has liver to break H2O2). If the plant lacks of CO2, H2O2 and NH3 will accumulate in side the plant and might create some negative effects.
Correct me if I'm wrong though!

[Rishi97]

Could someone please check my answer

When there is a pathogen:
Humoral immunity:
1)Macrophage recognises pathogen as ‘non-self’
2)Macrophage engulfs the pathogen and displays its antigen on its surface
3)T-helper cell identifies the threat and releases interleukins which stimulate the activity of B cells.
4)B cells differentiate into B-plasma cells and B-memory cells
5)The B-plasma cells make antibodies which fight against the antigen.
6)Whilst the B-memory cells, remember the antibodies produced so when the antigen returns, the body can make more antibodies against that particular antigen in less time.

Thanks

[swagsxcboi]

Could someone please check my answer

When there is a pathogen:
Humoral immunity:
1)Macrophage recognises pathogen as ‘non-self’  how?
2)Macrophage engulfs the pathogen and displays its antigen on its surface
3)T-helper cell identifies the threat and releases interleukins which stimulate the activity of B cells. how does the T helper cell identify the macrophage?
4)B cells differentiate into B-plasma cells and B-memory cells you can't say B cells in general. You'd have to say that the selected B cell with antibodes specific to that antigen.
5)The B-plasma cells make antibodies which fight against the antigen. mention that the plasma B cells produce antibodies that then leave the cell (and become part of the blood plasma)
6)Whilst the B-memory cells, remember the antibodies produced so when the antigen returns, the body can make more antibodies against that particular antigen in less time. memory B cells will produce membrane bound antibodies that will initiate an immune response if the cell comes into contact with that specific antigen.

Thanks

your answers suggest you understand humoral immunity, but try to work on your phrasing.
also someone else will have to confirm but you might not be able to mention T cells in humoral immunity

[Reus]

Would have to agree completely with swagsxcboi there, Rishi.

[Rishi97]

oh really? I can't mention T-cells at all?
How can I answer the question with just B-cells ?

[vox nihili]

For the macrophage question, I don't think you'd need to say how. It's not part of your course.

Importantly, you've also failed to mention that it's not T-cells that activate B-cells. They are part of it co-stimulating B-cells,but B-cells actually need to bind an antigen to be activated.

[katiesaliba]

Are natural killer cells and cytotoxic T-lymphocytes similar in function? I understand that natural killer cells are non-specific and are therefore a part of the 2nd line of defence, however both kinds of leukocytes destroy infected cells, right? They both secrete perforin and destroy cells which display MHC-1-antigen complexes, right? Can someone please clarify the similarities and differences between both cells

[simpak]

Yup, they have similar function.  The major difference is NK cells are innate (as you have said) so they don't recognise specific antigens.  NK cells kill without a TCR and without needing to recognise a nonself antigen whereas T cells must recognise a nonself antigen expressed on MHC in order to kill, and T cells have a TCR.
Both the similarities you have listed hold true.

[Sense]

With a question asking what the first line of defence against a mosquito carrying yellow fever is... Is it just the skin and bodies reaction ? Or can it include repellent etc. ? I'm just wondering because it asks for 3 ways the first line will prevent getting the virus and I can't even think of 3 for a mosquito?


What course of action would Australia take for an unvaccinated person wanting to re enter Australia after being in a high risk zone of yellow fever ?

What chemicals are present in the blood of a person with an auto immune disease and that of someone without the disease ?

[simpak]

The mosquito would inject the virus directly into the bloodstream so the mosquito allows it to bypass the skin as a first line of defence.  I would say that the first line of defence in that case is an innate blood cell - probably a neutrophil since those are most abundant in the blood (more so than macrophages, but definitely some kind of phagocyte).  However, I guess you could say, as the mosquito still needs to bite to transmit the virus the skin still acts as a first line of defence?  I was always taught for mosquito vector viruses that the skin wasn't considered a proper defence mechanism, though.

The unvaccinated people would probably need to undergo serological testing to see if they had been exposed to yellow fever (ie look for antibodies against the virus).  Or have their blood tested for the presence of actual yellow fever viral particles.

The third question doesn't quite make sense to me - is it a question on the sac, or is it a question you've designed yourself?  It might be referring to antibodies specific to self antigens, but not all autoimmune disease are antibody mediated. Some rely more heavily on T cells (eg Type I Diabetes).

[katiesaliba]

Are these things still on the bio course:
-Guard cells
-ABO blood types
-Designer drugs