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Two Phases Of Photosynthesis

Two Phases Of Photosynthesis

Photosynthesis process used by plants to convert light energy from sunlight into starch or sugar, and carbon dioxide is released as a waste material. Photosynthesis, the process of converting light to fuel, is the most important process in a plant’s life cycle. Two Phases Of Photosynthesis are light reactions and dark reactions. Dark reactions also known as Calvin cycle.

The first step of Photosynthesis is the absorption of Carbon Dioxide. The second step is the production of glucose from starch. The third step is the use of an end product of Photosynthesis, glucose, to energize the living cells of the plant.

Two Phases Of Photosynthesis

The two phases of photosynthesis are:

1) Light reactions also called as photochemical reactions is the first stage of photosynthesis that converts the light energy into sugar.

2) Calvin Cycle or light-independent reaction or dark reactions or carbon fixation reactions is the second stage of photosynthesis that converts sugar into energy in the form of Adenosine triphosphate (ATP) by cellular respiration.

A) Light Reactions:

Light reactions occurs in the grana which are stacked membrane present within the chloroplasts.

– Splitting of water takes place that provides electrons and protons (hydrogen ions, H+). It gives off oxygen as the by-product.

– Chlorophyll absorb the light that transfers electrons and hydrogen ions produced from water to an acceptor called as Nicotinamide adenine dinucleotide phosphate (NADP+).

– NADP+ is reduced to NADPH by adding electrons with H+. It also produces ATP by using chemiosmosis. This is called photophosphorylation.


In this process, light is absorbed by the chlorophyll and stored as ATP. Oxygen is released by the breakdown of water. NADPH are used to store H+ ions. Light energy generates NADPH and ATP. These molecules store energy in their chemical bonds that is to be used in the dark phase.

B) Dark Reactions:

Dark reactions takes place in dark or in night and in stroma.

– The cycle starts by carbon fixation process that incorporates carbon dioxide into organic compounds.

– The fixed carbon then reduces into carbohydrate by adding electrons. The reducing power is given by NADPH that is produced in the light reactions.

– The carbon dioxide then converted into carbohydrate by using chemical energy from ATP. ATP also produced by light reactions.


In light-independent reaction, ATP and NADPH that are produced in light reactions will be used to convert CO2 into glucose.

End product of photosynthesis

Photosynthesis is a series of photosynthetic reactions in which the food material is converted into starch or sugar, and carbon dioxide is released as a waste material. The Photosynthetic reaction in plants is a complex process that involves three major functions namely the absorption of light, fixing of the energy in the form of chlorophyll and the utilization of the energy to build a structure vital to the life of the plant.

The Photosynthesis produce two different end products: Glucose and Oxygen. By product of photosynthesis process is oxygen. Glucose is stored during Photosynthesis. The glucose molecules are transported across the cell membrane to the chloroplast and to the next level of Photosynthesis.

Sucrose is formed from glucose. It is the main sugar plants that is transported to other parts of plant.

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