Intro to photosynthesis (article) | Khan Academy (2024)

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• Paarth Tara

  6 years agoPosted 6 years ago. Direct link to Paarth Tara's post “Okay, if the light depend...”

  Okay, if the light dependent reactions can create the ATP itself, then why not just transport that ATP everywhere instead of forming Glucose then spending a lot of other time in transforming back that Glucose into ATP?

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  (35 votes)

  • tyersome

    6 years agoPosted 6 years ago. Direct link to tyersome's post “Excellent question.The ...”

    

    

    

    Excellent question.

    The major reasons that I know of:
    1) The high energy bonds in ATP are (by definition) unstable, so for long term storage of energy ATP is not a good choice.
    2) In many situations phosphate is a limiting nutrient, so needing to make more ATP could severely limit the plants ability to store energy.
    3) Fixed carbon (e.g. glucose) can be converted into other molecules the plant needs including:
    • cellulose for structure
    • lipids for long term energy storage, cell membranes, etc.
    • proteins for structure, catalysis, etc.

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    (65 votes)
• Zepeda, Denver

  8 years agoPosted 8 years ago. Direct link to Zepeda, Denver's post “what is hydrolysis”

  what is hydrolysis

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  (17 votes)

  • Marianne

    8 years agoPosted 8 years ago. Direct link to Marianne's post “When you add water, you c...”

    

    When you add water, you can separate a compound into two. For example in hydrolysis of an ester, when you add water you get alcohol and carboxylic acid.

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    (20 votes)
• Lydia M

  8 years agoPosted 8 years ago. Direct link to Lydia M's post “Why is the first photosys...”

  Why is the first photosystem depicted in photosynthesis diagrams called "photosystem II" and the second photosystem called "photosystem I"? Are the names arbitrary or do they tell us something about the nature of how the photosystems work?

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  (8 votes)

  See Also

  Cellular respiration review (article) | Khan AcademyThe end products of aerobic respiration of glucose is-A. \[{{C}}{{{O}}_{{2}}}{{ + }}{{{H}}_{{2}}}{{O + ATP}}\] B. \[{\text{C}}{{\text{O}}_{\text{2}}}{\text{ + Pyruvic acid}}\] C. \[{\text{C}}{{\text{O}}_{\text{2}}}{\text{ + ethyl alcohol}}\] D. \[{\text{Biochemistry, GlycolysisWhat are the end product of photosynthesis ? Biology Q&A

  • Rick

    8 years agoPosted 8 years ago. Direct link to Rick's post “The reason for this is si...”

    

    

    The reason for this is simply because Photosystem I was discovered first, and Photosystem II was discovered second. You're right, it is confusing because the Photosystem II process occurs first, followed by Photosystem I.

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    (27 votes)
• 18plaitay

  8 years agoPosted 8 years ago. Direct link to 18plaitay's post “Why would you consider ph...”

  Why would you consider photosynthesis important ?

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  (0 votes)

  • Laurent

    8 years agoPosted 8 years ago. Direct link to Laurent's post “Photosynthesis is extreme...”

    

    

    Photosynthesis is extremely important! It is the process in plants that allows it to harness energy from sunlight and convert it into chemical energy that can be used by plants and other organisms. In fact all the energy we get from food is derived from the energy we get directly from plants or indirectly from animals that ate plants. Hence without the sun or plant's ability to carry out photosynthesis, there would be no energy to sustain most of the life on earth.

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    (29 votes)
• Noelia Cano

  8 years agoPosted 8 years ago. Direct link to Noelia Cano's post “Wait, so:ATP=Three Phosph...”

  Wait, so:ATP=Three Phosphates. ADP=Two Phosphates. What if there is only one Phosphate?
  What would it be called? And what would happen if there was only one phosphate?

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  (1 vote)

  • N Peterson

    8 years agoPosted 8 years ago. Direct link to N Peterson's post “ATP is Adenosine TriPhosp...”

    

    See Also

    Explainer: How photosynthesis works

    ATP is Adenosine TriPhosphate, with three phosphates, and lots of energy stored in bonds.
    ADP is Adenosine DiPhosphate, with two phosphates, and some energy stored in bonds.
    AMP is Adenosine MonoPhosphate, with a single phosphate group. These do not have energy stored in the bonds between phosphates, as there is only one.
    Biological processes add/subtract phosphates, changing these into each other.
    A related molecule, cAMP (cyclic AMP), has a cyclic structure, and rather than an energy storage role, it functions as a messenger in cell signaling pathways.

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    (13 votes)
• Sanglap Nahá

  8 years agoPosted 8 years ago. Direct link to Sanglap Nahá's post “The reactions occur witho...”

  The reactions occur without any dependence on light...so can it run during night time?...if so,in night time, the guard cells of the stomata close, so how can it take in carbon-dioxide to continue the cycle?...

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  (4 votes)

  • Marianne

    8 years agoPosted 8 years ago. Direct link to Marianne's post “Both reactions, the light...”

    Both reactions, the light-depended reaction and the Calvin's cycle OCCURS ONLY in the light (and out of color spectrum, mainly blue and red colors are used thus green reflected into your eye).
    1. Light-depended reaction gives you the NADPH
    2. You need NADPH in Calvin's cycle
    And you don't get the NADPH without light.
    EDIT after a comment brought up by Safwan: to be exact, The Calvin cycle needs light to start, but can continue for a while even without the light.

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    (4 votes)
• sheikhyahya4299

  6 years agoPosted 6 years ago. Direct link to sheikhyahya4299's post “do all other biological m...”

  do all other biological molecules are derived from carbs.

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  (5 votes)

  • tyersome

    6 years agoPosted 6 years ago. Direct link to tyersome's post “Good question!The answe...”

    Good question!

    The answer is yes. Plants make sugars through photosynthesis, but then convert some of that sugar into lipids and amino acids.
    https://www.bbc.com/education/guides/z23ggk7/revision/4

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    (1 vote)
• Morgan

  7 years agoPosted 7 years ago. Direct link to Morgan's post “What does the Pi stand fo...”

  What does the Pi stand for in the pictures describing light reactions and the Calvin cycle?

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  (2 votes)

  • Safwan S. Labib

    7 years agoPosted 7 years ago. Direct link to Safwan S. Labib's post “Pi stands for inorganic P...”

    Pi stands for inorganic Phosphate... It is described in chemistry as the phosphoryl group, i.e. PO3 with a 2- charge.... This phosphate bonds with the adenosine group to form AMP, ADP, ATP, and the like. Hope this helps

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    (4 votes)
• Arjo Dasgupta

  4 years agoPosted 4 years ago. Direct link to Arjo Dasgupta's post “In our school, we are doi...”

  In our school, we are doing an experiment where the rate of photosynthesis is being measured using different coloured waters. We mixed blue, red and green food colouring with water and then light was shone on them including clear water. Elodea plant was used. The data measured using an oxygen probe shows that the plant in clear water produces oxygen faster and green comes in second but blue and red produces oxygen slower. Why is that? Shouldn't red produce oxygen faster as red has the highest wavelength among other colour? Why does clear water produce oxygen fastest and why does green produce oxygen faster even though the colour of the plant is green?

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  (1 vote)

  • Davin V Jones

    4 years agoPosted 4 years ago. Direct link to Davin V Jones's post “It is likely that your co...”

    It is likely that your colored water is not purely filtering those individual wavelengths. As such, the green water is still allowing some blue and red wavelengths to pass, while the blue and red water is isolating more to only their ends of the spectrum.

    Since green still allows some of both blue and red to pass, chlorophyll from both ends of the spectrum still reacts with light and thus you have production on both ends. Whereas, with the blue or red water, primarily only the chlorophyll associated with those individual spectra can react.

    For a rough illustration, if you assume the light curves below and chlorophyll A absorbs blue light and chlorophyll B absorbs red. For the green curve, A and B get about 50% light. For the blue curve, the A is getting about 75% light and B is getting 0%, and vice versa for Red curve. So green is getting a weighted average of 50% reaction rate while Blue or Red get about 37.5% reaction rate.

    | A - B |- A B |A B-
    | / \ | \ | / 
    | / \ | \ | /
    |/ \ | \ | / 
     Green Blue Red

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    (6 votes)
• Aatmann Patel

  5 years agoPosted 5 years ago. Direct link to Aatmann Patel's post “What happens after the pl...”

  What happens after the plants form glucose and oxygen? What happens to the oxygen when it is released?

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  (3 votes)

  • @K@$H

    5 years agoPosted 5 years ago. Direct link to @K@$H's post “Glucose is utilised in re...”

    Glucose is utilised in respiration and excess glucose is stored in the form of starch....
    The o2 released might be utilised by humans etc

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    (3 votes)