Reef Chemistry Question of the Day #62 Gas Exchange 3 Photosynthesis

[Randy Holmes-Farley]

Reef Chemistry Question of the Day #62

Photosynthesizing organisms need carbon dioxide in order to make biomolecules.

The most simplified chemical equation describing photosynthesis is:


carbon dioxide + water + light --> carbohydrate plus oxygen


or in a chemical formula:


CO₂ + H₂O --> CH₂O + O₂


The concentration of free carbon dioxide in seawater is quite low, and getting enough of it into the interior of organisms fast enough can become a problem since it happens fairly slowly.

Which of the following is not a way that photosynthesizing marine organisms take up carbon dioxide? Note that some organisms use more than one of these choices.

A. Simple passive uptake of carbon dioxide by allowing it to randomly diffuse across their cell membranes
B. Protein transporters in cell membranes actively take up carbonic acid from the outside with the expenditure of energy
C. Carbonic anhydrase, an enzyme both inside and outside of cells, converts the more plentiful carbonic acid rapidly into free carbon dioxide to passively cross the membrane
D. Protein transporters in cell membranes actively take up bicarbonate from the outside with the expenditure of energy, and convert it into carbon dioxide
E. Cells pump out H⁺, converting extracellular bicarbonate into carbonic acid, which is then treated like choice B
F. Cells pump out OH^-, converting carbonate into carbon dioxide, which then enters cells like choice A.
G. Calcification by corals produces H⁺, which is used to convert interior bicarbonate into carbonic acid then to free carbon dioxide

Good luck!



























.

 

[beaslbob]

I have absolutely no idea

 

[Paintguru]

7...

 

[Randy Holmes-Farley]

7...

7?

The choices were letters.

 

[Cory]

I'll say A because they are simple organisms. But perhaps simple organisms or rather complex!

 

[beaslbob]

I'll say A because they are simple organisms. But perhaps simple organisms or rather complex!

but a is too simple for a Dr. Randy Holmes-Farley reef question of the day.:bigsmile:

 

[Randy Holmes-Farley]

but a is too simple for a Dr. Randy Holmes-Farley reef question of the day.:bigsmile:

Catching on, are you.

 

[H2O]

I got $1 on F

 

[DFW]

E, or, uh...........

 

[Randy Holmes-Farley]

And the answer is...F. Cells pump out OH^-, converting carbonate into carbon dioxide, which then enters cells like choice A.

Looks like H2O wins a dollar.

F is just nonsense that I made up. OH^- and carbonate (CO₃^--) won't react or combine in any way.

All of the other mechanisms are described in this article:

http://reefkeeping.com/issues/2006-10/rhf/index.php

 

[beaslbob]

...Looks like H2O wins a dollar.
...

I thought H2O just got to keep the dollar. :bigsmile:

 

[Randy Holmes-Farley]

I thought H2O just got to keep the dollar. :bigsmile:

OK, good point. He gets to keep his money.

 

[H2O]

Thanks . even a broken clock is right twice a day I got one or 2 out of 60 let's not make this a holyday

 

[beaslbob]

Thanks . even a broken clock is right twice a day I got one or 2 out of 60 let's not make this a holyday

with my luck I have a 24 hour clock. :xd: