VCE Biology Question Thread

[cosine]

Also ATP is synthesised from ATP synthase in the light-dependent stage. What is it exactly used for in the calvin cycle?

Thanks

[Reus]

So RuBP (5C) is attached to a CO2 molecule via Rubisco, then what?

It creates an unstable 6C-phosphate which decays into two molecules of glycerate 3-phosphate (3PG). This is an intermediate molecule produced in the Calvin cycle.

This is too deep into photosynthesis, we're just touching on it at uni haha

[cosine]

It creates an unstable 6C-phosphate which decays into two molecules of glycerate 3-phosphate (3PG). This is an intermediate molecule produced in the Calvin cycle.

This is too deep into photosynthesis, we're just touching on it at uni haha

So if the CO2 is attached to the 5C(RuBP) molecule, where does the oxygen gas go from the CO2?
Also, the 5C becomes 6C now, as the carbon has been added. When it is broken into two 3C molecules, an NADPH loaded molecule attaches H+ ions to the 3C molecules to create a 3-carbon sugar phosphate molecule. Where does the phosphate come from??

Thanks Marco

[cosine]

Also, two 3-Carbon sugar molecules are formated, now what? How exactly is glucose formed from this?

[mahler004]

Also, two 3-Carbon sugar molecules are formated, now what? How exactly is glucose formed from this?

Through glucneogenesis (https://en.wikipedia.org/wiki/Gluconeogenesis). Not in VCE.

Interestingly, the exact opposite of glycolysis.

[cosine]

Through glucneogenesis (https://en.wikipedia.org/wiki/Gluconeogenesis). Not in VCE.

Interestingly, the exact opposite of glycolysis.

Are these correct:

Light-dependent:
Inputs: Light energy, H20, NADP, ADP+Pi
Outputs: O2, NADPH+, ATP

Light-independent:
Inputs: NADPH+, ATP, CO2
Outputs: NADPH, ADP +Pi, Glucose, H2O(?)

Thanks

[StupidProdigy]

Hey can someone please explain why my guess is wrong for the last part of the question!? I got no feedback, just the mark so I'm not sure why it is wrong. Thanks!
http://imgur.com/9KpVnDQ
bump!!

[cosine]

Has anyone done the photosynthesis prac yet? What questions should I be expecting?
Thanks

[grannysmith]

Are these correct:

Light-dependent:
Inputs: Light energy, H20, NADP, ADP+Pi
Outputs: O2, NADPH+, ATP

Light-independent:
Inputs: NADPH+, ATP, CO2
Outputs: NADPH, ADP +Pi, Glucose, H2O(?)

Thanks

Yep, looks good to me. With H2O as an output of the light independent stage, this is correct but I don't think you'd lose marks for excluding it.

Hey can someone please explain why my guess is wrong for the last part of the question!? I got no feedback, just the mark so I'm not sure why it is wrong. Thanks!
http://imgur.com/9KpVnDQ

Sorry, I can't seem to view it clearly. :/

Has anyone done the photosynthesis prac yet? What questions should I be expecting?
Thanks

Inputs, outputs, brief description of each stage, compensation point and experimental design questions. So this could be testing for starch etc. which would indicate whether photosynthesis has occurred or not. Factors affecting the rate of photosynthesis have been  omitted from the study design iirc

[StupidProdigy]

Sorry, I can't seem to view it clearly. :/

As in my writing or the actual question on the paper? If it's the first that doesn't matter too much, I'll just compare it to what you think!? thankyou

[EspoirTron]

So if the CO2 is attached to the 5C(RuBP) molecule, where does the oxygen gas go from the CO2?
Also, the 5C becomes 6C now, as the carbon has been added. When it is broken into two 3C molecules, an NADPH loaded molecule attaches H+ ions to the 3C molecules to create a 3-carbon sugar phosphate molecule. Where does the phosphate come from??

Thanks Marco

Although I haven't touched Photosynthesis in a while I'll take a shot. The phosphate usually comes from ATP, with the  third phosphate group being of high energy, and thus, can be cleaved by a kinase enzyme in an exergonic reaction (iirc).

[mahler004]

So if the CO2 is attached to the 5C(RuBP) molecule, where does the oxygen gas go from the CO2?
Also, the 5C becomes 6C now, as the carbon has been added. When it is broken into two 3C molecules, an NADPH loaded molecule attaches H+ ions to the 3C molecules to create a 3-carbon sugar phosphate molecule. Where does the phosphate come from??

Thanks Marco

Can't really explain this properly without reference to the structures (look here https://commons.wikimedia.org/wiki/File:Calvin-cycle4.svg).

- The oxygen doesn't go anywhere. The oxygen in photosynthesis is evolved in the light reactions (in the oxygen evolving complex.) Both oxygens in CO2 are incorporated into the transient six-carbon intermediate.

The phosphate again is part of the ribulose 1,5 bisphosphate molecule (bis = two phosphate.) The phosphate is re-added later on by a kinase.

It's not really correct to speak of a 'NADPH loaded molecule.' NADPH is a molecule.

[cosine]

Can't really explain this properly without reference to the structures (look here https://commons.wikimedia.org/wiki/File:Calvin-cycle4.svg).

- The oxygen doesn't go anywhere. The oxygen in photosynthesis is evolved in the light reactions (in the oxygen evolving complex.) Both oxygens in CO2 are incorporated into the transient six-carbon intermediate.

The phosphate again is part of the ribulose 1,5 bisphosphate molecule (bis = two phosphate.) The phosphate is re-added later on by a kinase.

It's not really correct to speak of a 'NADPH loaded molecule.' NADPH is a molecule.

The book I use refers to NADP+ as a carrier molecule, and when it's occupied by a H+ ion, they use the term 'loaded'..?

Thanks anyway!

[EspoirTron]

The book I use refers to NADP+ as a carrier molecule, and when it's occupied by a H+ ion, they use the term 'loaded'..?

Thanks anyway!

I think what your textbook means by 'loaded' is the ability of NADPH to produce energy - albeit quite implicitly. NADPH is an electron carrier, remember that. Now NADPH upon oxidation can donate its electrons in the electron transport chain. This, in combination with the liberation of H+ can facilitate chemiosmosis to synthesis ATP through ATP synthase. "Loaded" is an interesting way to put it I guess. I'd probably call it an electron carrier more than anything else.

[vanessa14]

Has anyone done the enzyme SAC yet?
We mixed starch and water together (which was our control) then added iodine later.
The colour was blue black in the end, can someone explain why? 

And does anyone have any practise questions I good do that have done the SAC?
What things should I study?

Thank you so much to whoever answers in advance!