Question

Connecting link between light phase and dark phase of photosynthesis is
A. Only ATP
B. Only $NAD{H_2}$
C. Only $NADP{H_2}$
D. Both A and C

Answer 1

Hint: The mechanism of photosynthesis in plants takes place in light and dark phases. During the light reaction the splitting of water into oxygen, protons and electrons takes place. In the dark reaction there is no splitting of water.

Complete answer:
Photosynthesis is the process of capturing light energy and transforming it into chemical energy. Green plants use light energy and convert carbon dioxide and water into glucose. Oxygen is produced as a by -product. It regulates the proper balancing between oxygen and carbon dioxide in the atmosphere.
Photosynthesis takes place in plant leaves usually occurs in two ways: Light phase and dark phase
Light phase: The process happens in the thylakoids membrane and needs a constant supply of photons or light energy. It is known as the photochemical unit of photosynthesis. NADP utilizes hydrogen ions to form NADPH. Chlorophylls utilize the energy and form ATP and NADPH. Water molecules are changed into oxygen by this method.
The light absorption occurs with the help of photosystem I and photosystem II. At the end of light reaction ATP and NADPH are produced which are used in dark reactions to produce glucose from carbon dioxide.
Dark phase: It takes place in the stroma or matrix of chloroplast and can take place in the absence of light. The hydrogen coming from the NADPH sums up with carbon dioxide. There is no splitting of water and photolysis in this. It takes up ATP and NADPH produced from the light reaction to break down carbon dioxide.
This process helps in forming carbon sugar that creates glucose. Dark reaction does not say that it will occur at night only. It can occur in the day or night. Glucose produced in the dark reaction is formed by the utilization of carbon dioxide molecules. This occurs with the help of the Calvin cycle which is a part of the dark reaction.

Hence, the correct answer is option (D).

Note: The light reaction is a light dependent process and includes a series of events like light absorption, hydrolysis, the release of oxygen, ATP formation and NADPH formation.
The dark reaction is a light independent reaction which is a carbon fixing reaction. It occurs with the help of the Calvin cycle which is a part of the dark reaction.