Why does photosynthesis need light?

Question

Penelope Adams · Accepted Answer

Light provides energy for the synthesis of glucose from carbon dioxide and water during photosynthesis.

Photosynthesis is a photo-chemical reaction involving 2 main steps, i.e. Light reaction or Hill’s reaction and Dark reaction or Blackmann’s reaction.

Light reaction occurs in presence of light. Dark reaction can occur in absence of light but is dependent upon the end product of light reaction. Thus light reaction must precede dark reaction.

During light reaction, the chlorophyll entraps light and the solar energy is converted into chemical energy in the form of ATP molecules. This can happen because light energy is used to split water. The products of this reaction are oxygen (yeah for us heterotrophs!) and hydrogen ions. The hydrogen ions are used to make the ATP mentioned earlier.

Here is a video showing the formation of oxygen in the light reaction.

Video from: Noel Pauller

ATP molecules provide energy for the synthetic reactions during dark reaction of photosynthesis and are converted into ADP molecules.

ADP molecules, thus, formed during dark reaction are reconverted into ATP molecules during light reaction.

Light is, thus, necessary for the process of photosynthesis to provide energy for the synthetic reactions.

The synthesis of ATP molecules in presence of light is termed photo-phosphorylation.

Sebastian Alvarado · Answer

undefined Light is essential to photosynthesis because it drives the chemical reactions that turn carbon dioxide and water into glucose and oxygen. Chlorophyll in chloroplasts facilitates this process, which is what gives plants food and oxygen and, in the end, keeps life on Earth alive.

Isabella Anderson · Answer

undefined Photosynthesis requires light because it is the primary source of energy for the process. Light energy is absorbed by chlorophyll molecules in the chloroplasts of plant cells, initiating the photosynthetic reactions. This light energy is used to power the conversion of carbon dioxide and water into glucose and oxygen. Without light, the photosynthetic process cannot occur, as it is the driving force behind the synthesis of glucose, which serves as the primary source of energy for plants and ultimately for all living organisms that depend on them.