Some Photosynthesis Questions

[Anonymous]

OK, I know the light wavelegnths that are used by plants are in the 700nm for PSI and the 680nm range for PSII, hence their green color.

What about the dinoflagellates? How do they alter the amounts of various pigments to maximize the rates of photosynthesis? They actually change the pigments of their chloroplasts? Do they do it by producing more carotenoid pigments?

I know the reaction cycle is CO2 + H2O ---sunlight---> O2 + C6H12O6(glucose)
How is the salinity in the H2O removed? What becomes of the NaCl? Is it removed through osmosis? And what becomes of the O2 that is produced? Is it released or used by the polyp along with the glucose for glycolysis? (Cellular respiration = C6H12O6 + O2 -----> CO2 + H2O) Where does the CO2 come from to start off the reaction? Does it come from the polyp's products of cellular respiration? Are the two that interactive that they share products to maintain a cycle?
Are both cyclic and noncyclic photosynthesis involved in the zooxanthellae? Is there any relationship between the ATP created by the zooxanthellae and what is used by the polyp?

I'm sure I'll think of more, but I just had a chemistry final and my brain hurts.

Scott

[This message has been edited by ScottC (edited 08 May 2001).]

[This message has been edited by ScottC (edited 08 May 2001).]

[This message has been edited by ScottC (edited 08 May 2001).]

 

[Anonymous]

Dam...my brain hurts from this question...of which I am going to have to look up some answers. And I thought I knew coral photosynthesis well!!

<<OK, I know the light wavelegnths that are used by plants are in the 700nm for PSI and the 680nm range for PSII, hence their green color.>>

yes.

<<What about the dinoflagellates? How do they alter the amounts of various pigments to maximize the rates of photosynthesis?>>

This is from Aquatic Photosynthesis by Falkowski and Raven (1997):

"Acclimation to light intensity is commonly reflected by increased levels of chlorophyllproteins at lower photon fluxes and vice-versa. This process is also transcriptionally and non-transcriptionally modiied by the redox status of the itersystem electron transport chain through a post-translationally regulated phosphorylation cascade. This regulation permits cells toincrease or decrease the rate of synthesis of chlorphll-protein complexes in response to irradiance levels. the response may or may not be coupled to the synthesis of reaction centers, and requires a molecular mechanism for integration of the signals between multiple genes in different compartments of the cell.

There is a lot more information on photoacclimation and pigments to irradiance on pp. 210-213, and I will share that if you want or cannot find the book. Also, I have a hundred pages or so of primary lit on photoacclimation in corals...let me see if I can address more below.

<< They actually change the pigments of their chloroplasts?>>

yes.

<< Do they do it by producing more carotenoid pigments?>.

more, less of changed composition...and this includes chlorophyll, not just carotenoids.

<<I know the reaction cycle is CO2 + H2O ---sunlight---> O2 + C6H12O6(glucose)>>

Water comes out the other side, too.

<<How is the salinity in the H2O removed? >>

Salt movement is controlled at the level of the plasmolemma and may include membrane pumps.

<<What becomes of the NaCl?>>

Excluded or included to maintian proper osmotic balance with surroundings...however, the presence of zoox inside a coral cell allows a relativelys table environment that minimizes energy expenditiure in this regard.

<< Is it removed through osmosis?>>

yes and see above

<<And what becomes of the O2 that is produced? Is it released or used by the polyp along with the glucose for glycolysis?>>

Good question. It appears that the majority is used by the coral animal, with excess being eliminated...thus we see bubbles on the surface of corals sometimes at high noon in the wild and the tank...However, it can overproduce oxygen and this can become problematic at high rates of photosynthesis and can result bleaching episodes (see the required reading material on thsi subject)

<<(Cellular respiration = C6H12O6 + O2 -----> CO2 + H2O) Where does the CO2 come from to start off the reaction?>>

Either from coral respiration, seawater as CO2 or seawater equilibrium carbon sources of CO2, HCO3- or H2CO3 - we will discuss this quite a bit in the calcification lecture as there are tw main models... one points to carbon released by the process of calcification rather than directly from seawater.

<<Does it come from the polyp's products of cellular respiration? Are the two that interactive that they share products to maintain a cycle?>>

see above comment.

<<Are both cyclic and noncyclic photosynthesis involved in the zooxanthellae?>>

yes.

Is there any relationship between the ATP created by the zooxanthellae and what is used by the polyp?>>

Yes, and this is interesting. Generally, the zoox are nutrient limited by nitrogen. They are forced by the coral to release most of the high C products for use by the polyp, which takes the ATP's from splitting glycerol and other sugars, etc. in respiration. The zoox want that C for their own use, but can't becuase of coral mediated nutrient (N) limitation. If high N present in seawater, or produced by coral, the zoox will use it to produce proteins instead of glycerol, and then useit to reproduce..this results in less translated glycerol to the coral which ticks them off....and also results in unbalanced overgrowthof zoox and can result in coral expelling (bleaching) zoox form its tissue...so the symbiosis depends on permanent N limitation.

<<I'm sure I'll think of more, but I just had a chemistry final and my brain hurts.>>

I'm waiting. ;-) Nice questions!!!

Eric

 

[Anonymous]

Dam...my brain hurts from this question...of which I am going to have to look up some answers. And I thought I knew coral photosynthesis well!!

<<OK, I know the light wavelegnths that are used by plants are in the 700nm for PSI and the 680nm range for PSII, hence their green color.>>

yes.

<<What about the dinoflagellates? How do they alter the amounts of various pigments to maximize the rates of photosynthesis?>>

This is from Aquatic Photosynthesis by Falkowski and Raven (1997):

"Acclimation to light intensity is commonly reflected by increased levels of chlorophyllproteins at lower photon fluxes and vice-versa. This process is also transcriptionally and non-transcriptionally modiied by the redox status of the itersystem electron transport chain through a post-translationally regulated phosphorylation cascade. This regulation permits cells toincrease or decrease the rate of synthesis of chlorphll-protein complexes in response to irradiance levels. the response may or may not be coupled to the synthesis of reaction centers, and requires a molecular mechanism for integration of the signals between multiple genes in different compartments of the cell.

There is a lot more information on photoacclimation and pigments to irradiance on pp. 210-213, and I will share that if you want or cannot find the book. Also, I have a hundred pages or so of primary lit on photoacclimation in corals...let me see if I can address more below.

<< They actually change the pigments of their chloroplasts?>>

yes.

<< Do they do it by producing more carotenoid pigments?>.

more, less of changed composition...and this includes chlorophyll, not just carotenoids.

<<I know the reaction cycle is CO2 + H2O ---sunlight---> O2 + C6H12O6(glucose)>>

Water comes out the other side, too.

<<How is the salinity in the H2O removed? >>

Salt movement is controlled at the level of the plasmolemma and may include membrane pumps.

<<What becomes of the NaCl?>>

Excluded or included to maintian proper osmotic balance with surroundings...however, the presence of zoox inside a coral cell allows a relativelys table environment that minimizes energy expenditiure in this regard.

<< Is it removed through osmosis?>>

yes and see above

<<And what becomes of the O2 that is produced? Is it released or used by the polyp along with the glucose for glycolysis?>>

Good question. It appears that the majority is used by the coral animal, with excess being eliminated...thus we see bubbles on the surface of corals sometimes at high noon in the wild and the tank...However, it can overproduce oxygen and this can become problematic at high rates of photosynthesis and can result bleaching episodes (see the required reading material on thsi subject)

<<(Cellular respiration = C6H12O6 + O2 -----> CO2 + H2O) Where does the CO2 come from to start off the reaction?>>

Either from coral respiration, seawater as CO2 or seawater equilibrium carbon sources of CO2, HCO3- or H2CO3 - we will discuss this quite a bit in the calcification lecture as there are tw main models... one points to carbon released by the process of calcification rather than directly from seawater.

<<Does it come from the polyp's products of cellular respiration? Are the two that interactive that they share products to maintain a cycle?>>

see above comment.

<<Are both cyclic and noncyclic photosynthesis involved in the zooxanthellae?>>

yes.

Is there any relationship between the ATP created by the zooxanthellae and what is used by the polyp?>>

Yes, and this is interesting. Generally, the zoox are nutrient limited by nitrogen. They are forced by the coral to release most of the high C products for use by the polyp, which takes the ATP's from splitting glycerol and other sugars, etc. in respiration. The zoox want that C for their own use, but can't becuase of coral mediated nutrient (N) limitation. If high N present in seawater, or produced by coral, the zoox will use it to produce proteins instead of glycerol, and then useit to reproduce..this results in less translated glycerol to the coral which ticks them off....and also results in unbalanced overgrowthof zoox and can result in coral expelling (bleaching) zoox form its tissue...so the symbiosis depends on permanent N limitation.

<<I'm sure I'll think of more, but I just had a chemistry final and my brain hurts.>>

I'm waiting. ;-) Nice questions!!!

Eric

 

[Anonymous]

<<Salt movement is controlled at the level of the plasmolemma and may include membrane pumps.>>

OK.. The seperation of NaCl from salt water is done with energy consuming active transport? Which cells hold the pump?(electrogenic pumps?)
OK, I understand that the plasmolemma is an intergral part of plant cells, but to say they are responsible for the seperation leads me to believe the animal cells allow saltwater to enter it's tissue to get to the zoox. Is that correct?


Another quick thing I'd like to get into more detail with later.. The recognition of zoox by the polyp cells... it's believed to be enzyme-recognition related? Is there maybe a plasmid incoorporated in the animal cell's genetics that help it recognize the zoox? Maybe it sees it as something that belongs to it? Has there been any work done on similarities in the sequences of nitrogenous bases between the two organisms?



[This message has been edited by ScottC (edited 09 May 2001).]

 

[Anonymous]

<<The seperation of NaCl from salt water is done with energy consuming active transport? Which cells hold the pump?(electrogenic pumps?)
OK, I understand that the plasmolemma is an intergral part of plant cells, but to say they are responsible for the seperation leads me to believe the animal cells allow saltwater to enter it's tissue to get to the zoox. Is that correct?>>

Probably determined at both coral plasma membrane, vacuole membrane, and plant cell membrane levels. Sure corals allow salt in.
Also, active transport may be part. We'll see that also passive diffusion will enter into it through channels in calcification lecture.

<<The recognition of zoox by the polyp cells... it's believed to be enzyme-recognition related? Is there maybe a plasmid incoorporated in the animal cell's genetics that help it recognize the zoox? Maybe it sees it as something that belongs to it? Has there been any work done on similarities in the sequences of nitrogenous bases between the two organisms? >>

See my other post on reference sources for more investigation...if you find anything more conclusive, please let us know..It has been a couple years since I looked into this.

eric