VCE Biology Question Thread

[Sine]

Are aerobic respiration and photosynthesis opposites? Like they have opposite reactants and products but other than that they make energy for the cell or organism? Is that it? Are they opposites? 

Thanks

at a vce level as a whole I think its definitely okay to think of them as opposites tbh

Although they do have differences e.g. Cellular respiration has 3 stages, photosynthesis has 2 stages

[PhoenixxFire]

They aren’t really opposites. In photosynthesis light energy is used to make glucose, in cellular respiration glucose energy (i dunno what it’s called haha) is used to make chemical energy (ATP).

So the reactents and products are opposites but really they are both ways of changing the form of energy.

Edit: As Sine said though, if it helps you remember it you can think of them as opposites.

[vox nihili]

On the whole the reactions are opposites, but it's certainly not sufficient to only think of them this way. You need to know more about the details.

For example, photosynthesis uses an electron transport chain to convert light energy into ATP, which is then used to fuel the production of glucose.

In cellular respiration, the electron transport chain is the final step, and is used to produce ATP for cellular processes.

In this way they don't really serve as opposites.

[darkz]

So this is basically an experiment where a plant was in an air tight chamber and exposed to radioactive carbon dioxide and I was just wondering why the % of pyruvate is constant at 0% - shouldn’t the plant be undergoing respiration and thus produce pyruvate?

[sweetcheeks]

My educated guess is that the glucose-phosphate hasn't been utilised yet in the respiration pathway (it has many different fates in the cell such as starch storage). Maybe it has been stored and other glucose molecules are being used up. I would say that given enough time, you would likely see C14 being detected in the pyruvate.

[vox nihili]

So this is basically an experiment where a plant was in an air tight chamber and exposed to radioactive carbon dioxide and I was just wondering why the % of pyruvate is constant at 0% - shouldn’t the plant be undergoing respiration and thus produce pyruvate?

You’d expect so. I imagine, maybe, that the level of respiration was so low that you don’t see the oyruvate?
It also depends on where they extracted the chemicals from. If it were the chloroplasts only, then this would be very reasonable and explain why your pyruvate is zero

[TheBigC]

So this is basically an experiment where a plant was in an air tight chamber and exposed to radioactive carbon dioxide and I was just wondering why the % of pyruvate is constant at 0% - shouldn’t the plant be undergoing respiration and thus produce pyruvate?

I had a crack at this question previously, having removed my answer due to making far too many assumptions within it until finally acknowledging the lack of parsimony and, in an act to prevent misguidance, I thought it be best to remove. I was hoping that darkdzn could provide us with more information regarding the stem of the question to fetch clues.
Hopefully, then, I can provide a sound, less-ramshackle, answer.

[darkz]

I had a crack at this question previously, having removed my answer due to making far too many assumptions within it until finally acknowledging the lack of parsimony and, in an act to prevent misguidance, I thought it be best to remove. I was hoping that darkdzn could provide us with more information regarding the stem of the question to fetch clues.
Hopefully, then, I can provide a sound, less-ramshackle, answer.

Hey, here's some added info

[vox nihili]

Hey, here's some added info

Having had a fresh look, I’ve got the answer no point giving it away though...

Tell me how does our labelled carbon get into pyruvate?

[darkz]

Having had a fresh look, I’ve got the answer no point giving it away though...

Tell me how does our labelled carbon get into pyruvate?

Well the radioactive carbon dioxide would be fixed/reduced into organic carbon in the light independent reactions and then forms G3P => glucose. From there, the glucose (6C) with radioactive carbon is used in respiration to form pyruvates (3C) in glycolysis? So shouldn't they also be radioactive?

[TheBigC]

Well the radioactive carbon dioxide would be fixed/reduced into organic carbon in the light independent reactions and then forms G3P => glucose. From there, the glucose (6C) with radioactive carbon is used in respiration to form pyruvates (3C) in glycolysis? So shouldn't they also be radioactive?

Correct. This means there must be an alternative step occurring. I believe that the radioactive glucose-phosphate is being converted into sucrose, in converse to it pursuing the glycolysis pathway. However, I am still attempting to gauge why oxaloacetate immediately presents with high C-14 levels. (Vox, what is your answer?)

[PopcornTime]

I am measuring the rate of reaction by varying the temperature of an enzyme at 10ºC. Would varying the temperature at 5ºC instead of 10ºC improve accuracy or precision?

[PhoenixxFire]

It would improve accuracy. Precision means you get the same value every time whereas as accuracy is how close it is to an actual value. Varying temperature is a bit of a weird example but it would make the rate of reaction more accurate whereas otherwise you would be guessing the rate of reaction between the temperature values.

I’m actually not entirely sure on this though - I had to google the definition of precision

[TheBigC]

It would improve accuracy. Precision means you get the same value every time whereas as accuracy is how close it is to an actual value. Varying temperature is a bit of a weird example but it would make the rate of reaction more accurate whereas otherwise you would be guessing the rate of reaction between the temperature values.

I’m actually not entirely sure on this though - I had to google the definition of precision

You're correct Phoenix. It would affect accuracy, not precision.

EDIT: My assumption is that the individual is plotting a rate-temperature graph, thus smaller intervals (of temperature) would enable for a more accurate plot. It would, hence, aid in deducing an optimal temperature of the enzyme.

[vcestressed]

I am measuring the rate of reaction by varying the temperature of an enzyme at 10ºC. Would varying the temperature at 5ºC instead of 10ºC improve accuracy or precision?

I am measuring the rate of reaction by varying the temperature of an enzyme at 10ºC. Would varying the temperature at 5ºC instead of 10ºC improve accuracy or precision?

I agree with the answers above but do you have to talk about accuracy or precision for this? I feel like this is referring more to validity than accuracy. I did a similar prac and talked about accuracy when I compared my experimental data to the actual 'optimal temperature' of the enzyme (which was found online). You can talk about precision by looking at scatter when you draw a line of best fit on your graph.