Can anyone explain Light Reaction and Dark Reaction?

Question

Answer

Light reaction - Light dependent, occurs in Grand, photolysis of water and formation of ADP and NADPH and Dark reactions- Light Independent, occurs in stroma, use of ADP and NADPH

Answer

Light reaction occurs during daytime.
Dark reaction takes place during night.

Answer

Light Reaction:
The light reaction is the first stage of photosynthesis, which occurs in the thylakoid membrane of the chloroplasts in plant cells. It converts light energy from the sun into chemical energy in the form of ATP and NADPH.

Process:
1. Absorption of Light: Chlorophyll and other pigments in the thylakoid membrane absorb light energy from the sun.

2. Splitting of Water: This absorbed energy is used to split water molecules into oxygen, protons (H+), and electrons. This process is known as photolysis.

3. Electron Transport Chain: The high-energy electrons released from water move through a series of electron carrier molecules embedded in the thylakoid membrane. As they move, they release energy, which is used to pump protons across the membrane, creating a proton gradient.

4. ATP Synthesis: The proton gradient drives the synthesis of ATP through ATP synthase. ATP is the energy currency of the cell.

5. NADPH Formation: Another set of high-energy electrons from the electron transport chain combine with NADP+ (nicotinamide adenine dinucleotide phosphate) and H+ ions to form NADPH, which is a molecule that carries energy and is used in the next stage, the dark reaction.

Dark Reaction (Calvin Cycle):
The dark reaction, also known as the Calvin cycle, is the second stage of photosynthesis. It occurs in the stroma of the chloroplasts and uses the ATP and NADPH produced in the light reaction to convert carbon dioxide into glucose.

Process:
1. Carbon Fixation: In this step, carbon dioxide molecules are combined with a five-carbon compound called RuBP (ribulose-1,5-bisphosphate) using the enzyme RuBisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase). This results in the formation of a six-carbon compound, which quickly splits into two molecules of three-carbon compound called PGA (phosphoglycerate).

2. Reduction: ATP and NADPH from the light reaction are used to convert PGA into another three-carbon compound called G3P (glyceraldehyde-3-phosphate). This conversion involves the transfer of energy and electrons.

3. Regeneration: Some G3P molecules are used to regenerate RuBP, while others are used to produce glucose and other organic molecules. The regeneration of RuBP allows the cycle to continue.

4. Glucose Production: Two G3P molecules combine to form glucose, which can be used for energy or stored as starch.

Conclusion:
The light reaction captures light energy and converts it into chemical energy in the form of ATP and NADPH. This energy is then used in the dark reaction to convert carbon dioxide into glucose. Together, these reactions enable plants to produce their own food through photosynthesis.

Answer

Light reaction  light needed to produce organic energy molecules ATP and NADHPDark reactionno light needed Eastern dark reaction use ATP and NADHP  to produce energy molecules

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