Practice exam question

[the girl at the rock show]

Question 12
Why does the photosynthetic production of glucose in plants rely on the formation of ATP and NADPH in
the light-dependent reactions?
A. ATP and NADPH are required for chlorophyll to function properly.
B. The CO2 absorbed from the air must be combined endergonically with hydrogen from NADPH to
form glucose.
C. Active uptake of CO2 from the air into the leaf requires ATP; the CO2 is then combined with hydrogen
from NADPH to form glucose.
D. ATP and NADPH are important intermediates in the Calvin cycle.


This is a question from NEAP unit 3 2012. I'm confused about this question - the answer is C but I chose B. Why is B incorrect?

[Yacoubb]

Question 12
Why does the photosynthetic production of glucose in plants rely on the formation of ATP and NADPH in
the light-dependent reactions?
A. ATP and NADPH are required for chlorophyll to function properly.
B. The CO2 absorbed from the air must be combined endergonically with hydrogen from NADPH to
form glucose.
C. Active uptake of CO2 from the air into the leaf requires ATP; the CO2 is then combined with hydrogen
from NADPH to form glucose.
D. ATP and NADPH are important intermediates in the Calvin cycle.


This is a question from NEAP unit 3 2012. I'm confused about this question - the answer is C but I chose B. Why is B incorrect?

I actually would have chosen B too. Because from what I know, the ATP produced in the light-dependent reaction provides energy for the reaction between CO2 and H from NADPH+ in the light-independent stage.

[psyxwar]

Since when was the uptake of CO₂ active? O_O

[Yacoubb]

Since when was the uptake of CO₂ active? O_O

That's what I thought - I always knew carbon dioxide as diffusing  into the leaves; how inefficient (energy wise) would it be for plants to photosynthesise if CO2 uptake is active o.O

[Stick]

NEAP are funny like this. :|

[the girl at the rock show]

Sorry guys! I meant D, not C! Typo :|

[psyxwar]

B is a vast simplification of the Calvin Cycle -- CO₂ doesn't actually combine with hydrogens from NADPH, it combines with Ribulose Bisphosphate (RuBP), a five carbon compound, forming a six carbon compound that almost immediately breaks down into 2 three carbon compounds which then go through the cycle eventually yielding 2 G3Ps (per 6 CO₂). Furthermore, NADPH provides reducing power necessary to convert one intermediate to the next (carboxyl -> aldehyde group); it's purpose isn't to provide hydrogen. ATP also isn't used in the process of NADPH reducing the 3 carbon intermediate, and B kind of implies this too, so it's wrong.

Knowing this, D is the most appropriate. However this is way way way beyond the scope of VCE Bio...

[the girl at the rock show]

B is a vast simplification of the Calvin Cycle -- CO₂ doesn't actually combine with hydrogens from NADPH, it combines with Ribulose Bisphosphate (RuBP), a five carbon compound, forming a six carbon compound that almost immediately breaks down into 2 three carbon compounds which then go through the cycle eventually yielding 2 G3Ps (per 6 CO₂). Furthermore, NADPH provides reducing power necessary to convert one intermediate to the next (carboxyl -> aldehyde group); it's purpose isn't to provide hydrogen. ATP also isn't used in the process of NADPH reducing the 3 carbon intermediate, and B kind of implies this too, so it's wrong.

Knowing this, D is the most appropriate. However this is way way way beyond the scope of VCE Bio...

Thanks. So I guess it's just a case of Neap going far beyond the course?

On a different note, where on earth did you learn all that?!

[psyxwar]

Thanks. So I guess it's just a case of Neap going far beyond the course?

On a different note, where on earth did you learn all that?!

Haha, yeah. I read beyond the course sometimes (when I can be bothered!). Try checking out some uni texts like Campbell's Biology. I reckon it gives you more of an understanding of the concepts = doing better.

[Stick]

Thanks. So I guess it's just a case of Neap going far beyond the course?

On a different note, where on earth did you learn all that?!

All that you need to know is that the Calvin cycle is just that - a cycle. Hydrogen is not directly added to carbon dioxide to form glucose; it occurs in a series of chemical reactions.

[the girl at the rock show]

Thanks. I kind of already knew that the light independent stage wasn't exactly just adding on H+ ions, but I would've thought that we wouldn't be expected to know enough about it to choose between A and D.

Here's another question. It's from STAV 2009 unit three.

Question 9
When comparing eukaryotic cells and prokaryotic cells it is reasonable to state that:
A. the lack of organelles in prokaryotic cells means that basic cellular functions are different in
prokaryotic cells compared to eukaryotic cells.
B. both prokaryotic cells and eukaryotic cells are able to compartmentalise biochemical processes
within the cell.
C. all membrane functions in prokaryotic cells takes place in the plasma membrane, whereas in
eukaryotic cells these functions occur in different organelles.
D. only eukaryotic cells are able to carry out photosynthesis as they have chloroplasts whereas
prokaryotic cells cannot photosynthesis as they do not have chloroplasts.

I chose A; the answer is C.

Haha, yeah. I read beyond the course sometimes (when I can be bothered!). Try checking out some uni texts like Campbell's Biology. I reckon it gives you more of an understanding of the concepts = doing better.

Yeah, I had someone suggest reading some uni books, but I really just can't be bothered haha. Doing these trial exams is cumbersome enough...

[Stick]

I guess it depends on what basic cellular functions are.

[pi]

Q9 is a bit ambiguous to me, VCAA would probably pay both A and C.

[the girl at the rock show]

I thought so too! Thanks.