Components of Photosynthesis

By Sawyer Howard
Photosynthesis takes place in the leaves of the plant.
spring leaf image by John Sfondilias from

Photosynthesis, a process that converts sunlight into energy, occurs in most plants. During photosynthesis, plants combine water, H2O, and carbon dioxide, CO2, with sunlight to produce sugar, C6H12O6. Every C6H12O6 molecule produced takes six H2O molecules, six CO2 molecules, and electrons from sunlight. Six molecules of Oxygen, O2, are also produced and released into the air. The sugar is stored for future use. There are two main parts of photosynthesis, a light-dependent reaction and a light-independent, or dark, reaction.


Chloroplasts, located in the leaves of most plants, are organelles found inside of mesophyll cells and are where photosynthesis actually takes place. The other components required to perform photosynthesis are found here. Light energy is stored in the thylakoid sacs, called the grana, which are locate in the chloroplast membranes. Light is gathered by chlorophyll and other pigments. CO2 and H2O are brought to the chloroplasts by the stomates and vascular bundles. Once all the materials are gathered, proteins, located in the grana, are used to convert the light into sugar.


carrots image by William Berry from

Pigments absorb the sunlight into the photosynthetic organism. Chlorophyll is the most common pigment found in plants. Because it reflects green light, absorbing only blue and red wavelengths, it makes most plants appear green. Chlorophyll gains electrons from the sunlight, moving them to a storage area by means of the porphryin ring. Caroteniods, only present in some plants, reflect red, orange and/or yellow wavelengths and absorb light wavelengths that chlorophyll does not.

Stomates and Vascular Bundles

Stomates are found primarily in the lower epidermis of leaves. Stomates are small holes that open and close as needed to allow CO2 to enter and O2 to exit. Their existence allows these molecules to pass in and out of the plant without the plant becoming dehydrating. Vascular Bundles are the veins seen in the leaves. They transport the water, as well as nutrients, throughout the plant. The tissue of these bundles, called xylem, directly transport water to the chloroplasts in the leaves.

Grana and Stroma

The grana, also referred to as the thylakoid membrane, is where the chemicals used to convert energy, CO2, and H2O into sugar are stored. It is here that the sugar is converted to its storage state, called adenosine triphosphate, or ATP, which is the sugar molecule, C6H12O6, combined with three phosphate groups and an adenine chain. Only the light reaction takes place in the grana. The dark reaction takes place in the stroma. The stroma is also located in the chloroplast's membrane and surrounds the grana. During this reaction, the chemicals in the stroma convert the ATP into usable energy via a process called the Calvin Cycle.