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34

71% of the earth's surface is taken up by water. Not surprisingly therefore, the seas are an important source of oxygen. National Geographic claims that photosynthesis by phytoplankton (mostly single-celled phototrophs, such as cyanobacteria, green algae and diatoms) account for half of the earth's oxygen production. The other half, they claim, is produced ...


9

Yes, it is possible, but not necessarily the case. Non-green leaves with chlorophyl: There are leaves that don't appear green, but do have chlorophyl and therefore can conduct photosynthesis. (See, for instance, refraction effects in white caladiums or the link in the answer by Resonating). Non-green leaves without chlorophyl: There are leaves that don't ...


8

I am not sure which class of organisms have the highest contribution in oxygen production but diatoms do have a significant contribution. The introduction in this paper says that diatoms account for 40% of marine photosynthesis which according to this site is "1/4 of the oxygen we breathe."


8

The reason that chlorophyll is green is because it absorbs other colors of light such as red and blue, so in a way the green light is reflected out since the pigment does not absorb it. Because life might have been purple: It is possible that the very first life form to process light may have been purple colored. This would mean it was reflecting red ...


7

As far as I can understand your question, you wish to know why a plant cell consumes ATP to produce glucose when it can directly use the ATP as an energy molecule. ATP is an energy currency and is required in different biochemical pathways. However, it is not a good energy storage molecule. Following are the reasons why production of an energy molecule ...


7

From the link given by @Kendall Such a gradient can be maintained because the thylakoid membrane is essentially impermeable to protons. I think this solves your dilemma of 'why not maintaining equilibrium' totally. The reason for this difference is that the thylakoid membrane is quite permeable to Cl- and Mg2+. The light-induced transfer of H+ ...


6

Trees are definitely not the only source of oxygen. First, all green plants do photosynthesis, not only trees. Moreover, about half of all photosynthesis on earth is done by microorganisms in the oceans known as phytoplankton.


6

Check out the excellent Wikimedia picture of the carbon cycle: All the numbers are in billions of tons of carbon: white = stored, yellow = natural flux, red = human contribution. Notice that the deep ocean stores much more accessible carbon than any other carbon cycle source, and is only surpassed by the lithosphere* in overall quantity of carbon stored ...


4

The difference in energy requirements of a motile species make photosynthesis an unsuitable form of primary energy generation for them. Since plants are sessile, their energy consumption rates are lower. Plants have approximate respiration:photosynthesis rates of 0.35-0.9, as can be seen in this table (click to enlarge): Once the energy consumption ...


4

There are several parts to my answer. First, evolution has selected the current system(s) over countless generations through natural selection. Natural selection depends on differences (major or minor) in the efficiency of various solutions (fitness) in the light (ho ho!) of the current environment. Here's where the solar energy spectrum is important as ...


4

In biology phosphorylation marks the addition of inorganic phosphate groups to proteins or other organic molecules. The phospho-group usually comes from ATP which is converted into ADP in this process. In the context of the Calvin Cycle there are two positions where molecules get phosphorylated. The first is the phosphorylation of 3-phosphogylcerate to ...


4

Sorry for the poor quality of the image, but its just as a reference for my answer. You have made the question too complex. From the figure, we find that 1 H2O gives 2 H+ and 2 e-. 2 e-, through quinone cycle, provide 4 H+ i.e. total 6 H+ which form 6/3 = 2 ATP i.e. 1 H2O => 6 H+ => 2 ATP Multiply this equation by 8 and you get: 8 H2O => 48 H+ => 16 ...


4

Disclaimer: This is going to be a very mathematical answer. Before answering it, I assume that you are only asking about humans, assuming that all other organisms don't require $O_2$ to survive (as it will complicate the answer many many times). List of variables: V = total volume of air on earth (in l) V' = total volume of oxygen on earth (in l) ...


3

OVERVIEW (verbatim from the article) Plastidic ferredoxin−NADP+ reductases (FNRs) accept electrons by two sequential one-electron transfer steps from two molecules of the one-electron donor ferredoxin to generate their fully reduced hydroquinone state, FNRrd, through the formation of an intermediate neutral semiquinone form, FNRsq. FNRrd then ...


3

Equation you have mentioned is balanced chemical equation. In reality these are series of Redox reactions, major two as follows, Oxidation of oxygen from water in presence of light (energy from photon), $ 2H_2O \xrightarrow{Photons} O_2 + 4H^*$ Ions produced from above reaction reduces carbon dioxide , $4H^* + CO_2 \rightarrow (CH_2O) + H_2O$ So ...


3

They do have chlorophyll, at least in general. There are a couple very rare exceptions, but if it can stand up on its own, it contains chlorophyll. The green is just washed out by a very bright red pigment.


3

Short answer: Electrons flow through membranes by floating through kind of channels made out of iron-sulfur clusters. Long answer: Let's take a look at the electron transport chain in the inner mitochodrial membrane. There is a proton gradient across the membrane building up a potential difference by pumping protons across the membrane as electeons flow ...


3

I can see your frustration if you meet errors such as NADPH2 but that is the price you pay for approaching as complex a subject as photosynthesis without a good biochemistry textbook. Even the on-line versions (e.g. Berg et al.) are unsatisfactory because of their layout. You will have to sit down and spend a couple of hours on the topic — all you can expect ...


3

I answered this implicitly in a comment to my answer to: Light and Dark Reaction of photosynthesis?. Anyway: There is no such thing as NADPH2. There is only NADP+ and NADPH. Consult Wikipedia or a reputable text such as Berg. The nicotinamide portion of NADP that undergoes oxidation and reduction is exactly the same as in NAD. The changes undergone are: ...


2

It’s not about the oxygen! This question indicates two misplaced concerns. One is with oxygen. I imagine that this is because of its importance to us as animals; however as far as photosynthesis is concerned oxygen is just a waste product. The other is with a chemical equation, which is as informative as the top line of a commercial balance sheet. One's ...


2

All photosynthesis reaction does need chlorophyll,even in cyanobacteria and algae the difference is the type of chlorophyll ( which depends on available wavelength of light and energy efficiency ) fully parasite plants on the other hand doesn't contain chlorophyll and this force them to live as parasites ( keep in mind that we do have half parasitic plants ...


2

I thought it was fairly well understood that trees make NO net contribution to the oxygen supply. As a tree (or any plant) grows, it locks carbon within itself and releases the O from the CO2 into the atmosphere. When that tree dies, it decays by being consumed. All of the C gets recombined with O2 during the decay. Therefore, a quantity of oxygen is lost ...


2

Why be mobile? To follow the sun? Plants are mobile. Their seeds are. We have plants living on other plants. Once they have a spot on the sun though moving does not necessarily improve your situation, being stationary and defending your territory though does. (Growing taller, deeper roots, wider crowns)


2

The photolysis of water is coupled to the reduction of plastaquinone (Q) in photosystem II (PSII) as summarized in this diagram, adapted from Berg et al.: The overall reaction (which balances) is: 2 H2O + 2 Q + 4 H+ = O2 + 2 QH2 + 4 H+ But the 4 H+ on both sides of the equation are not the same. The generation of the hydrogen ions in the thylakoid lumen ...


2

The main purpose of crystallizing a molecule or molecular complex like a Photosystem is usually to provide a crystal for X-ray crystallography. A crystal has its molecular components arranged in a structured systematic repeating pattern, and this repeated pattern allows the X-rays to reveal the 3-dimensional shape of one of the components. Knowing the ...


2

I think we can look at it like this Your noncyclic pathway liberates 4H+ from two water molecules. We're doing that because to get one O2, you've got to split 2H2O. This happens in photosystem II. So in the next step (you know, really broadly) the electrons are passed to cytochrome b6-f complex, where each electron allows it to pump 2H+ into the thylakoid ...


2

Electricity may be indirectly generated from plants through the use of a microbial fuel cell, in which biologically-catalyzed chemical reactions are used to drive an electrochemical cell. A non-technical description of the technology can be found here. The basic idea is that plants produce organic compounds, which are broken down by soil microorganisms to ...


2

It's not really possible to break it down this way. The CO2 fixated by the RUBISCO enzyme generates two phosphoglycerate (2 x 3C) molecules from one ribulose bisphophate molecule (5C), while the rest of the Calvin cycle serves to regenerate 3 ribulose bisphophate from 5 phosphoglycerate. Hence, one 3-carbon sugar (glyceraldehyde phosphate or dihydroxyacetone ...


2

This is a homework question but I will answer it (forgive me moderators ;). You will get your answer from this answer: Sucrose and starch are more efficient in energy storage when compared to glucose and fructose, but starch is insoluble in water. So it can't be transported via phloem and the next choice is sucrose, being water soluble and energy ...


2

But cyanobacteria do not seem to use polysaccharides in the same way as plant cells do (building materials, for example) The Calvin-Benson cycle produces glucose which is the starting material for a lot of biosynthetic pathways including that of the nucleotides (ribose from the pentose-phosphate pathway). Glycolytic intermediates are also involved in ...



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