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

learn more… | top users | synonyms

0
votes
1answer
12 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 ...
3
votes
0answers
54 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 ...
3
votes
2answers
97 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 = ...
3
votes
3answers
273 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 ...
0
votes
0answers
16 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 ...
6
votes
2answers
383 views

How is photosynthesis observed?

How is photosynthesis observed? Say I have plants A and B, and I want to find how fast they are able to turn carbon dioxide into oxygen. How would I experiment this? Say I have one plant A, which ...
1
vote
1answer
31 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 ...
5
votes
1answer
68 views

Total dark deprivation at day-neutral plants

First of all, I am not a biologist. Almost for a week, a question has come to my mind: "Is it harmful ceaselessly exposing a plant to light?" (I mean with natural & artificial light with ...
1
vote
1answer
450 views

Cyanobacterial photosynthetic oxygen yield

I am somehow not convinced that biotic factors are solely responsible for creating 21% of atmosphere (around 40 million moles of oxygen). There may be additional issues here. Since cyanobacteria ...
8
votes
1answer
96 views

Primary Productivity of Oceans

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 ...
1
vote
0answers
12 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 ?
5
votes
2answers
118 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 ...
1
vote
1answer
63 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 ...
5
votes
1answer
69 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 ...
1
vote
2answers
39 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 ...
3
votes
0answers
3k views

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. ...
14
votes
2answers
6k views

How does a plant grow before photosynthesis is possible?

During photosynthesis, a plant translates CO2, water and light into O2. I assume the carbon C is further used for the growing process. I wonder how the plant grows before the time where photosynthesis ...
0
votes
2answers
69 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.
9
votes
4answers
11k views

Why does the oxygen produced in the photosynthesis come from water and not CO$_2$?

In the photosynthesis equation $$6*CO_2+6*H_2O+sunlight\rightarrow C_6H_{12}O_6+6*O_2$$ the only place where we have 6 molecules of $O_2$ is in the $6*CO_2$. Then it reacts with $H_2O$ to form ...
3
votes
1answer
221 views

Where do the H+ ions come from in light reactions?

In the light-dependent reactions of photosynthesis, H+ ions pass to the thylakoid space. Where do these protons come from?
1
vote
1answer
44 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?
9
votes
1answer
1k views

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 ...
3
votes
0answers
68 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 ...
6
votes
1answer
264 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 ...
8
votes
1answer
1k views

Do immature fruits perform photosynthesis?

Most immature fruits are green: peppers, pine cones, plums, lots of them. I want to know if the green is from chlorophyll in the cells. Do the fruit cells perform photosynthesis? When you cover a ...
1
vote
0answers
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?
0
votes
1answer
4k views

Why would the stroma have a higher pH during photosynthesis?

Here is a question form my test. If you could measure the pH of the interior of thylakoids and the surrounding stroma during active photosynthesis what would be the relative pH of each? The ...
0
votes
1answer
70 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 ...
4
votes
1answer
91 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+ ...
7
votes
2answers
276 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 ...
1
vote
0answers
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? ...
6
votes
4answers
6k views

Do plants with non-green leaves have chlorophyll and photosynthesis?

Is it even possible that plants with non-green leaves have chlorophyll, and do such non-green leaved plants carry out photosynthesis?
0
votes
0answers
132 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 ...
1
vote
1answer
2k views

What part of the cactus photosynthesizes?

In general, plants photosynthesize through their leaves and, to a much lesser extent, through their stems. Cacti, however, have no visible leaves, but instead spines. In what part of the cactus does ...
0
votes
0answers
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 ...
1
vote
0answers
18 views

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 ...
5
votes
1answer
795 views

What types of light can't a plant photosynthesize in?

I have a plant on my desk, and it got me to wondering: Can my plant use the light from my monitors to photosynthesize? If so, what light (apart from green light, to a degree) can't plants use to ...
3
votes
1answer
82 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 ...
0
votes
1answer
72 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 ...
7
votes
1answer
5k views

Does photosynthesis occur on cloudy days or does it require direct sunlight?

In my basic science classes in high school, I have learned that during photosynthesis, plants absorb sunlight and produce food by converting carbon dioxide and water into sugar and starch. To me, ...
5
votes
4answers
1k views

Photosynthesis: What Powers the Splitting of Water?

The splitting of water is an endergonic (non-spontaneous) reaction, and thus would require energy (chemical work to be done) in order to happen. In Photosystem II, an enzyme catalyzes this splitting, ...
0
votes
0answers
17 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 ...
-1
votes
1answer
433 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
votes
1answer
54 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 ...
1
vote
1answer
22 views

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 ...
1
vote
0answers
132 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 ...
2
votes
0answers
66 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 ...
0
votes
0answers
73 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 ...
1
vote
1answer
71 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 ...
0
votes
1answer
178 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 ...