VCE Biology Questions Thread

S007

lune777 According to VCAA, you probably already read it while marking, but if you didn't, they wrote that the treatment would be most effective when the mean decrease in prescriptions is the lowest (year 9). As this study is done over many years, no significant increase in the need for prescriptions signifies the long-term and sustained effects, hence option A.
Despite the big jump between the first and second years, it still became increasingly effective over the years. So, the AIT does have a long-term sustained effect.

sarah99

Hey just wondering if photorespiration is slower than/produces less O2 photosynthesis?

I came across a question about an underwater plant Elodea - and whether O2 production (as output counted by number of bubbles) would increase decrease or stay the same if the students added more O2 to the solution.

I was thinking since technically the calvin cycle will still use up ATP and NADPH and re-cycle the unloaded forms back to LDS, they can be used and O2 can be produced again, so maybe it would have no effect?

S007

O2 production would stay the same because its not involved in the calvin cycle. for a plant to produce O2 it just needs water. the water enters the LDS and is split into 2 hydrogens and oxygen. Two oxygens from split water then join together to form O2 and then are released whereas the H+ is taken up by NADP+ so becomes NADPH and the hydrogen is used in the LIS to make the final product glucose. is that what you were asking about? let me know. if it was I hope it made sense

sarah99

yes makes sense - thanks!! I was also thinking the same thing. I was also considering that light independent stage will unload ATP and NADPH into ADP and NADP+ right, so possibly if photorespiration is slower than photosynthesis, these co-enzymes might reach the light dependent stage slower, meaning O2 produced might be less.
but yeah, not sure and might not be tested

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