What is Light Reaction, Dark Reaction, and Hill Reaction?

Light Reaction

It is the initial stage of photosynthesis, in which series of biochemical reactions takes place that requires light energy which is captured by light-absorbing pigments 'chlorophyll' to convert into chemical energy in the form of ATP and NADPH (supplement).

These reactions take place on the thylakoid membranes of the chloroplast.

Dark Reaction

It is the second step of photosynthesis, also known as a carbon-fixing reaction. It is a light-independent process in which sugar molecules are formed from the carbon dioxide and water molecules and also utilizes the energy from ATP and NADPH to produce glucose.

These reactions take place in the stroma of the chloroplast.


The Hill Reaction

The reaction is termed as Hill Reaction as it was first demonstrated by the well-known British biochemist “Robin Hill” in 1930.

He proposed that the isolated chloroplasts from plants can release oxygen (O2) in the absence of carbon dioxide (CO2).

It is defined as the photoreduction of an electron acceptor (such as ferricyanide) by the hydrogens of water, with the evolution of oxygen during the light-dependent (sunlight) steps of photosynthesis.


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