Definitions of Chloroplasts

What are Chloroplasts

What are Chloroplasts?

Chloroplasts are the cellular organelles of vegetables and green algae that are responsible for photosynthesis.

Chloroplasts are found in eukaryotic organisms, are found in large numbers, and their sizes are variable, usually ovate or spherical.

Likewise, chloroplasts fulfill different roles in plants, which is why they are evenly distributed in the cytoplasm of cells.

On the other hand, chloroplasts are characterized by having an envelope made up of two concentric membranes that have thylakoid vesicles, which contain photosynthetic pigments, such as chlorophyll, and other substances that transform light energy into chemical energy.

Therefore, the importance of chloroplasts lies in the transformation of light energy into chemical energy for vegetables, plants and green algae, that is, in photosynthesis.

Chloroplast structure

The structure of the chloroplasts is presented below.


The chloroplast has two membranes, one internal and one external.

  • External membrane: delimits the chloroplast, is permeable, so it has transporter proteins, and separates it from the cytoplasm.
  • Inner membrane: it folds into the chloroplast and contains thylakoids, whose appearance resembles a flattened sac.
  • Thylacodial membrane: it is found in a stroma and is where the thylakoids are grouped in the form of a scarlet.


The stroma is the aqueous part found in the inner membrane, which contains circular DNA molecules, RNA, ribosomes, lipids, cotton granules, among other substances. The genetic process of the chloroplast and the reactions of photosynthesis take place in the stroma.

Also, within the stroma is the thylakoid membrane.


Thylakoids are flattened saccules delimited by the thylakoid membrane and can be found in isolation, overlapping and interconnected. The thylakoids are organized in a stacked manner and each of these stacks is called a grana.

It is in the thylakoids that the processes of photosynthesis of plants are carried out.

Chloroplast function

The main function of chloroplasts is to carry out photosynthesis, a process in which the light phase that occurs in the thylakoid membrane (production of ATP and NADPH), and the dark phase that takes place in the stroma (CO fixation) are carried out. 2 through the Calvin Cycle and carbohydrates are formed).

In addition, chloroplasts perform the biosynthesis of fatty acids through carbohydrates, ANDPH and ATP, and also reduce nitrates to synthesize amino acids.

What are Chloroplasts