Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organisms' activities (energy transformation). This chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water – hence the name photosynthesis, from the Greek φῶς, phōs, "light", and σύνθεσις, synthesis, "putting together".In most cases, oxygen is also released as a waste product. Most plants, most algae, and cyanobacteria perform photosynthesis; such organisms are called photoautotrophs. Photosynthesis is largely responsible for producing and maintaining the oxygen content of the Earth's atmosphere, and supplies all of the organic compounds and most of the energy necessary for life on Earth.

The first step of photosynthesis is the excitation of electrons of chlorophyll. The energy from the sun, raises an energy level in the chlorophyll molecule, causing electrons to leave the molecule and travel along the electron transport chain (ETC) in a series of oxidation and reductions.

Excitation of Electron of Chlorophyll

Photosynthesis is the process by which green plants and some other organisms convert light energy into chemical energy. It occurs in the chloroplasts of plant cells and involves a series of complex reactions. The first step of photosynthesis is the excitation of electrons of chlorophyll, which is the pigment responsible for capturing light energy.

Chlorophyll
- Chlorophyll is a green pigment found in the chloroplasts of plant cells. It is responsible for absorbing light energy from the sun.
- There are two types of chlorophyll: chlorophyll a and chlorophyll b. Both types absorb light energy from different wavelengths.
- Chlorophyll molecules are embedded in the thylakoid membranes of the chloroplasts.

Excitation of Electrons
- When light energy is absorbed by chlorophyll molecules, electrons in the molecule become excited.
- The energy from the absorbed light raises the electrons to a higher energy level.
- This energy is used to convert the light energy into chemical energy, which is stored in the form of ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate).
- The excited electrons are transferred to electron carriers, such as NADP+, which then become reduced to NADPH.

Role of Excited Electrons
- The excited electrons are used to drive the production of ATP and NADPH, which are essential for the subsequent steps of photosynthesis.
- ATP is a molecule that stores and releases energy for cellular processes.
- NADPH is a coenzyme that carries high-energy electrons and hydrogen ions, which are used to power the synthesis of glucose and other organic molecules.

Overall Significance
- The excitation of electrons of chlorophyll is the first step in the process of photosynthesis.
- It allows plants to capture light energy and convert it into chemical energy, which is used to produce glucose and other organic compounds.
- This process is vital for the survival of plants and the production of oxygen, which is released as a byproduct of photosynthesis.

Therefore, the correct first step of photosynthesis is the excitation of electrons of chlorophyll.