what is the main difference between light reaction and dark reaction???
Answers
Explanation:
Photosynthesis is the process of conversion of light energy into chemical energy which can then be utilized by living organisms. It is a rather complex process which is carried out through various stages.
Photosynthesis comprises two phases:
The first phase is the photochemical phase or light-dependent process. This phase is commonly known as the light reaction.
The second phase is the biosynthetic phase of the dark reaction of photosynthesis. This phase is the light-independent process.
The whole process of photosynthesis takes place within the chloroplast.
Light Reaction and Dark Reaction
As stated above, photosynthesis occurs in two phases – light reaction and dark reaction.
Light Reaction
The light reaction is a light-dependent process which includes a series of events such as light absorption, hydrolysis, the release of oxygen, formation of ATP and NADPH.
The light reaction of photosynthesis initiates only when it is supplied with light energy.
The photosystem is the arrangement of pigments, including chlorophyll within thylakoids.
There are two photosystems in plants:
Photosystem I (PS-I)
Photosystem II (PS-II)
Photosystem I absorbs light at a wavelength of 700 nm, whereas Photosystem II absorbs light at a wavelength of 680 nm.
The light reaction occurs in the thylakoids of the chloroplast. When the light hits, chlorophyll a get excited to higher energy state followed by a series of reactions. This energy is converted into energy molecules ATP and NADPH by using PS I and PS II. Also, hydrolysis occurs and releases oxygen.
Also Read: Cyclic and non-cyclic photophosphorylation
Dark Reaction
Dark reaction is also called carbon-fixing reaction. It is a light-independent process in which sugar molecules are formed from the carbon dioxide and water molecules.
The dark reaction occurs in the stroma of the chloroplast, where they utilize the products of the light reaction.
Plants capture the carbon dioxide from the atmosphere through stomata and proceed to the Calvin cycle.
In the Calvin cycle, the ATP and NADPH formed during light reaction drives the reaction and convert six molecules of carbon dioxide into one sugar molecule, i.e. glucose.
Also Refer: Photosynthesis in Higher plants
Difference between Light and Dark Reaction
Following are the important differences between light and dark reaction:
Light Reaction
Dark Reaction
It takes place only in the presence of light.
It can take place in the presence or absence of sunlight.
It is a photochemical phase.
It is a biochemical phase.
It takes place in the grana of the chloroplast.
It takes place in the stroma of the chloroplast.
NADP utilizes H+ ions to form NADPH.
The hydrogen of NADPH combines with CO2.
The end products are ATP and NADPH.
Glucose is the end product. ATP and NADPH help in the formation of glucose.
The water molecules split into hydrogen and oxygen.
Glucose is produced. Co2 is utilized in the dark reaction.
Photolysis occurs in PS-II.
Photolysis does not occur.
Answer:
LIGHT REACTION
Light reaction is the stage of photosynthesis which occurs only in the presence of sunlight and it is dependent on the light to perform its work.It takes place in the grana thylakoid membrane of the chloroplast .The grana thylakoid is responsible for trapping the solar energy for photosynthesis.
DARK REACTION
Dark Reaction is the stage of photosynthesis which occurs in the presence or absence of the light.It is is not dependent on light to perform its reaction.It take place in the Stroma of the chloroplast.The stroma is responsible for enzymatic reaction to synthesis of glucose to form starch.
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