The process by which light energy is harnessed to assemble organic compounds (esp. glucose) from inorganic carbon dioxide.

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Is volume preserved in the usual photosynthesis reaction equation?

Is volume preserved in the usual photosynthesis reaction equation? 6CO2 + 6H20 --> C6H12O6 + 6O2 When I compute volume of LHS, I get 2.21 x 10^-19 cm^3 ...
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32 views

anabolism in plants

The question is as following: Which substance has the greatest contribution to the anabolism of glucose in plants. A- Oxygen (O2). B- Water (H2O). C- carbon dioxide (CO2). The official answer given ...
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3answers
72 views

Can plants grow without photosynthesis?

Animals can survive without eating if nutrition is injected directly into their blood. Can the equivalent be done with plants? By injecting carbohydrate rich nutrient solution, either without ...
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43 views

“CO2 is plant food” - What is the actual effect of increased CO2 on plant growth?

A frequent talking point by global warming deniers is that CO2 in the atmosphere is actually beneficial because "CO2 is plant food". I'm a non biologist trying to figure out under what circumstances ...
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22 views

How does plant life obey the constraint that the change in Gibbs free energy in a reaction must be negative?

My understanding is that if a reaction takes place, either entropy of the system must rise, or energy must be released from the system as heat, or both. (Citation: paraphrasing from The Vital Question,...
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69 views

Is QIAPI 1 a scam?

I find it strange that there isn't a wikipedia article on a drug that allegedly modulates human photosynthesis. I thought I might get a virus from some of the sites selling it, but others seemed ...
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54 views

Photosynthesis and its subtopics [closed]

Which of the following statements about photosynthesis is true? a. Photosynthesis is an energy consuming process b. The light-dependent reactions produce the energy-rich compounds that are used up ...
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74 views

Doubt in a multiple choice question involving cell organelles

Find the odd one out and state the category of the rest. Chloroplast Mitochondria Nucleus Grana Now my answers are : 1st possibility : grana Category : presence of DNA in ...
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27 views

How does an increase in CO2 concentration affect Photosynthesis and Transpiration

I noticed a strange thing in my book. At one place it says that an increase in CO$_2$ concentration in the outside air decreases the rate of transpiration but at the other place it says that an ...
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14 views

When is Pheophytin used in electron transfer to the q cycle in plants?

If I understand it correctly: (short version) The Q cycle starts with PQH2 it removes the 2H(+) and gives one electron to Plastocyanin and the other to a stored Plastoquinone to charge it to ...
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382 views

How long could Earth's oxygen supply last if no new oxygen were produced? [closed]

I read in an article or heard in some documentary that there's so much oxygen in the atmosphere that even if all photosynthesis stopped, there's already enough to last us a long time. Is this ...
3
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59 views

Are plants really oxygen neutral?

This accepted and most upvoted answer to the question Does grass alone produce enough oxygen for life? claims that plants are oxygen neutral: Plants are oxygen neutral The question wording is a ...
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20 views

Photosynthetic Absorption Spectrum - Pigment vs. Absorption Spectrum

This is a very confusing question to me that came up while I was studying photosynthesis. Halobacterium has a photosynthetic membrane that is colored purple. Its photosynthetic action spectrum is ...
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34 views

Opening and Closing of stomata

Which is the more accepted theory for the opening and Closing of stomata : the sugar concentration theory or the k+ ion theory ?
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1answer
97 views

Is there nothing such as NADPH2? [duplicate]

I have gone through various sites and some say there is NADPH2 and some say there is no NADPH2 there's only NADP+ ...WHich is the correct view....Please dont mark this answer as duplicates since I ...
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43 views

What did cyanobacteria gain from photosynthesis?

As far as I understand, cyanobacteria began performing photosynthesis long before plant cells as we know them arrived on the scene. But cyanobacteria do not seem to use polysaccharides in the same way ...
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119 views

Light and Dark Reaction of photosynthesis?

I'm having a hard time understanding light and dark reactions because all the sites I've gone through provide different equations. Some say photolysis is H20 = H+ + O2 while some present it as H20 = H+...
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540 views

Why upper surface of leaves is more green and shiny than the lower one?

I have properly googled this and got various answers. However, those answers do not provide an answer to the "Why" part of my question. Why is it that the upper surface of leaves is more green than ...
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2answers
93 views

Can photosynthesis take place if the plant is kept in ice cold water or not?

Can photosynthesis take place in a plant even if the plant is kept in ice cold water? I have googled this question, but so far have not found a satisfactory answer.
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1answer
58 views

In flowering plants food is transported in which form? [closed]

In flowering plants food is transported in which form? I searched on google and found that it is sucrose. Why not glucose/fructose/starch?
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Why is chlorophyll green? Isn't there a more energetically favorable color? [duplicate]

Chlorophyll being green means it absorbs light in the red and blue area of the spectrum. Isn't this the high and low energy light? Wouldn't plants get more energy if they absorbed light in the green ...
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95 views

Behavior of plant guard cells: open or closed stomata

On an exam of mine, I had the following question: The interaction between the guard cells and stomata in a plant leaf can be seen in the diagram below. In which scenario could the guard ...
5
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1answer
70 views

How are ions 'pumped' across a membrane during electron transport?

A number of sites (including this one) that provide descriptions of photosynthesis state that high energy electrons 'pump' ions across a membrane. What is the actual 'pumping' mechanism? I've looked ...
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11 views

A question regarding rate of photosynthesis increases [duplicate]

If we keep on increasing CO2 concentration in atmosphere, will the rate of photosynthesis increases or not?
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72 views

How are 6 “fixed” CO2 molecules joined toegther as glucose?

When we study calvin cycle, we study it with 6 molecules so as to form 1 glucose in a single cycle as: 6 RuBP + 6 CO2 => 12 3-PGAL => 1 Glucose + 6 RuMP But if we look deep, then we know that the ...
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1answer
93 views

Why it seems that principles of chemistry are not being applied in this biochemical process? [closed]

According to an answer in this question, my concept used below does not apply: In the non-cyclic photophosphorylation, consider splitting of two water molecules, then 4 e- (electrons) and 4 H+ (...
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1answer
36 views

How can I estimate the CO₂ uptake of a plant?

I would like to make an estimation of the CO2 uptake of plants I cultivate, including, lettuce and aromatic herbs, such as thyme, basil, rosemary. What I want is to end up with a rough indicator for ...
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33 views

About photosynthesis VS respiration [closed]

Is it true to say that the electron transport chain in photosynthesis and respiration is slightly different, regarding to the direction of H+ pumping and flowing back in through ATP synthase? ...
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380 views

Why is ATP produced in photosynthesis used to synthesize glucose?

In photosynthesis ATP is produced in light-dependent reactions only to go to the Calvin cycle to be turned into glucose to make ATP during respiration: Why isn't this ATP just directly released ...
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147 views

How do CAM plants keep stomata closed by day and open at night?

I understand how plants open stomata, with the H+ ion removal and the resulting K+ ion influx in the guard cells to induce turgor (wikipedia article here), though not how this process relates to ...
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290 views

How many ATP are formed?

What is the number of ATP molecules formed during the photosynthetic processes which consume 8 molecules of $\text{H}_2\text{O}$ due to noncyclic electron transport and subsequent photophosphorylation?...
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22 views

About electrons returning to photosystem I when supply of NADP runs out in photosynthesis

According to my textbook, in photosynthesis, when the supply of NADP runs out, electrons from photosystem I return to the electron transport chain that links the 2 photosystems and flow back to ...
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Can you grow more Biomass in a brickhouse only powered by solar cells than in a greenhouse? Will we ever be able to?

So I asked following question some physicists but they couldn't really help me though: Right now I read that 1m² of solar cells generates roughly 100Watts of energy. There are really efficient ...
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177 views

Why are oceans said to have “low productivity” in terms of photosynthesis?

80% of the world's photosynthesis takes place in the ocean. Despite this, oceans are also said to have low productivity - they cover 75% of the earth's surface, but out of the annual 170 billion ...
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86 views

By what mechanism is NADP+ converted to NADPH in Photosystem I? [closed]

Here is my current understanding: $\mathrm{NADP^{+}}$ takes 2 electrons from Ferredoxin at the end of the electron transport chain to generate $\mathrm{NADP^{-}}$. An $\mathrm{H^{+}}$ ion in the ...
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19 views

Lighting device efficacy for plant growth

Background Consider the following technologies: 100 lm/W OLED (2008, source) 303 lm/W LED (2014, source) 94 lm/W LEP (2015, source) For growing food, the preferred measurement is ...
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447 views

Where is energy stored in a molecule of ATP? [closed]

Where is energy stored in a molecule of ATP? How is energy released from a molecule of ATP? What specific bond needs to break What is the difference between ATP and ADP? Define pigment a. What ...
2
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1answer
58 views

Chemosynthesis in Bacteria

The light reactions, if seen as a whole, are basically the oxidation of water to provide energy (ATP) to fuel the Calvin Cycle. The photons provide the activation energy for the same. How then can ...
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Does the location of the double bond in chlorins yield a distinct biological function?

Chlorins differ by the number of double bonds and their location. Chlorin has 20 pi electrons, whereas bacteriochlorin and isobacterichlorin have 18 pi electrons, but at different locations. Do ...
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151 views

Trouble understanding how uncouplers in the thylakoid membrane increase the rates of the Electron transport chain?

I am a undergrad in a cell physiology class and just did a learning exercise involving testing rates of the electron transport chain via the reduction of DCPIP, analyzed by spectrophotometry. ( I ...
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79 views

Is there a plant particularly suitable for absorbing Hydrogen Sulfide

I live in an area with some open sewers and in the morning I can usually can smell the gas inside my house. There are many plants like snake plant which improve indoor air quality but I was ...
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Experiment to show that carbon dioxide is needed for photosynthesis

In my school test, the question is as follows: Will the experiment work satisfactorily? What alterations can you make to obtain expected result? What I wrote: Yes, it will work satisfactorily. ...
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86 views

pH concentrations during photosynthesis

I'm studying for an AP Bio exam and had the following question: Which of the following parts of an illuminated plant cell would you expect to have the lowest pH? (A) Stroma (B) Cytosol ...
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1answer
81 views

Photosynthesis Equation

The equation for photosynthesis is $\ce{6CO2 + 6H2O + Energy -> C6H12O6 + 6O2}$ My confusion rests in the following: during the photolysis (water-splitting) step of the light reactions that ...
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1answer
203 views

Can electricity be harvested from the soil around plants? [closed]

This is a rehash of a question I originally wrote on Skeptics which got moved to Physics, but I'm really after an answer from a biological perspective. A device called the E-Kaia is making news by ...
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1answer
79 views

What happens to H+ when Glycerate 3-Phosphate is converted to Triose Phosphate?

The conversion from Glycerate 3-Phosphate to Triose Phosphate requires: $ATP \rightarrow ADP + P_i$ $NADPH \rightarrow NADP + H^+$ So what happens to the $H^+$? Is it in-effect "recycled" back to ...
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1answer
124 views

What do the numbers in Photosystem I P700 and Photosystem II P680 stand for? Is it the optimum wavelenght? The maximum wavelenght?

I am a bit confused about this because my teacher and english Wikipedia say it's the wavelenght the Photosystem is most reactive to; my textbook and the german Wikipedia say that it is the maximum ...
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1answer
51 views

How long can a plant generate oxygen from its own carbon dioxide, produced during nighttime?

I recently bought one of these miracle fruit plants (Synsepalum dulcificum). Since they are of tropic origin, they need higher humidity and temperature as we have it here in Austria. So I decided to ...
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74 views

How to calculate PAR and aPAR from reflected + incoming radiance

i have measured the reflected radiance of a plant and the incoming radiance with a point spectrometer from 300 to 700 nm in 1nm increments. How can i calculate photosynthetically active radiation (PAR)...
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84 views

The definition of leaf area index

In many textbooks, leaf area index (LAI) is defined as the total leaf area per unit ground area. I want to know LAI is defined only by leaves that are directly above the ground (e.g., perpendicular ...