Meaning of Chloroplasts

What are Chloroplasts:

Chloroplasts are the cellular organelles of plants and green algae that are responsible for carrying out photosynthesis.

Chloroplasts are found in eukaryotic organisms, they are found in large numbers and their sizes are variable, they are usually oval 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 composed 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.

See also Photosynthesis.

Structure of chloroplasts

The structure of chloroplasts is presented below.


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

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


The stroma is the aqueous part found in the inner membrane, which contains circular DNA molecules, RNA, ribosomes, lipids, granules of starch, among other substances. The chloroplast genetic process and photosynthesis reactions 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. Thylakoids are organized in a stacked manner, and each of these stacks is referred to as grana.

It is in the thylakoids that the processes of photosynthesis in plants take place.

Chloroplast function

The main function of chloroplasts 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 occurs in the stroma (CO2 is fixed through the Calvin Cycle and carbohydrates are formed).

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

See also Calvin Cycle.

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