Biology Unit 3 Questions Megathread

[Kaille]

Can anyone provide some sort of a "formula" that can be applied to design an experiment questions?

[dooodyo]

Hey guys,

I need some help on this question. Any help would be much appreciated.

If asked to write down the balanced equation of photosynthesis would it be
correct to write:
                              light
1.   6CO2 + 6H20 -------------> C6H12O6 + 602
                          chlorophyll  

or


                                light
2.   6CO2 + 12H20 -------------> C6H12O6 + 602 + 6H20   ?        
                            chlorophyll


Oh and also why does the nature of biology textbook say that photosynthesis is most efficient in
light of blue and red wavelengths when it also says that in T.W Engelmann's experiment that violet was
where most oxygen was released (i.e. the highest rate of photosynthesis) ?

 Thanks heaps in advance.

[HERculina]

second one
a picky examiner will more likely take points off the 1st one (i think)

[dooodyo]

Haha yeah thats what I thought aswell, thanks for that Hercules 

Do you happen to know the answer to my second question?

Thanks in advance.

[WhoTookMyUsername]

do T cells proliferate as soon as they come into contact with an APC or do they find a B cell first (is this costimulation?)

how do cytotoxic T cells proliferate if they don't come into contact with antigen?




EDIT: IN VCAA 2010 in question 6 SA part c)

http://www.vcaa.vic.edu.au/vcaa/vce/studies/biology/pastexams/2010/2010biol1-w.pdf

Is the diagram inaccurate? Compound R almost appears to be an enzyme catalysising the reaction of Q into S, but the answers suggest Compound R can be turned INTO S as in an alternative metabolc pathway, is the diagram incorrect, or is this always how metabolic pathways are drawn?

Can someone please expain or linnk to a site expalining metabolic  pathway diagrams / alternative metabolic pathway diagrams, i looked through my texts and notes, as well as online but i couldn't find anything 
Thanks

[shinny]

Haha yeah thats what I thought aswell, thanks for that Hercules 

Do you happen to know the answer to my second question?

Thanks in advance.

Because violet is essentially a sub-section of blue, and is the specific wavelength which is best absorbed. The first statement is just a bit of an oversimplification by breaking colour down into red, green and blue, and its saying that largely, red and blue are most absorbed, leaving green behind which gives plants their green colour.

[WhoTookMyUsername]

VCAA 2010 says red is better absorbed than blue

[Russ]

do T cells proliferate as soon as they come into contact with an APC or do they find a B cell first (is this costimulation?)

They don't proliferate "as soon as" they meet their Ag but they don't need to find a B cell first. Costimulation is just signals provided by an APC to trigger proliferation.

how do cytotoxic T cells proliferate if they don't come into contact with antigen?

What makes you think they don't...? How else would they be activated?

Is the diagram inaccurate? Compound R almost appears to be an enzyme catalysising the reaction of Q into S, but the answers suggest Compound R can be turned INTO S as in an alternative metabolc pathway, is the diagram incorrect, or is this always how metabolic pathways are drawn?

Diagram is accurate. Compound R is not an enzyme, it's a compound. It can be converted to S, just like Q can (but presumably a different mechanism).

Enzymes are written next to arrows, they don't get their own box.

[shinny]

VCAA 2010 says red is better absorbed than blue

I think it is for chlorophyll a. Chlorophyll b however has blue being absorbed better. Doesn't matter too much, they tend to give you the absorption spectra you need anyway.

[dooodyo]

Thanks heaps Shinny.

Oh and do we have to know those specific details about which chlorophyll absorbs which
wavelength of light better?

[jane1234]

Thanks heaps Shinny.

Oh and do we have to know those specific details about which chlorophyll absorbs which
wavelength of light better?

Not specifically (as in the exact wavelength) but just know that it absorbs blue and red light best (and sub-sections like violet etc), and reflects green.

[jane1234]

Freshwater plants were put in test tubes. Would the CO2 levels in the test tubes be high or low in the absence of light (night time)??

[lexitu]

Photosynthetic rate should be lower hence less CO2 consumption hence high CO2 concentration unless I'm missing something (which I almost definitely am).

[jane1234]

Photosynthetic rate should be lower hence less CO2 consumption hence high CO2 concentration unless I'm missing something (which I almost definitely am).

Yeah that's right according to the answers.
I just thought that since CO2 is required for the light-independent (usually dark) stage, levels would be lower...

[lexitu]

Yep, you're right in saying that about CO2 playing a role in the light-independent stage but the "dark stage" is a bit misleading - it doesn't have to occur at night, it's just that those reactions are not reliant on light as an energy input. So both light dependent and independent reactions would be occurring at much higher rates during daylights and therefore more carbon dioxide would be consumed.