# How do autotrophs capture the energy in sunlight?

Mar 17, 2018

Sunlight is absorbed by the green pigment, chlorophyll and the solar energy is converted into chemical energy in the form of $\text{ATP}$.

#### Explanation:

Autotrophs capture sunlight by the pigment chlorophyll and is used for the synthesis of glucose $\left({C}_{6} {H}_{12} {O}_{6}\right)$ from simple, inorganic substances like $C {O}_{2}$ and ${H}_{2} O$ during photosynthesis.

Photosynthesis occurs in 2 steps:

1. Hill's reaction

2. Dark reaction

Light reaction or Hill's reaction involves capturing sunlight and converting solar energy into chemical energy in the form of $\text{ATP}$. This occurs by breakdown of water into ${H}^{+}$ ions and ${O}^{2 -}$ ions. This is termed by photolysis of water. Excited electrons from ${O}^{2 -}$ pass through a series of electron carriers, losing energy during their passage. This energy is converted into $\text{ATP}$. The remaining${H}^{+}$ ions reduce $\text{NADP}$ to $\text{NADPH}$.

$\text{ATP}$ and $\text{NADPH}$ produced during light reaction are used in the dark reaction for reduction of $C {O}_{2}$ to ${C}_{6} {H}_{12} {O}_{6}$.