Plastids can be different: types, structure, functions

Many people almost know what plastids are, from a school bench. In the course of botany, it is said that in plant cells, plastids can be of various shapes, sizes, and perform various functions in the cell. This article will remind you of the structure of plastids, their types and functions to those who have graduated from school long ago, and will be useful to everyone who is interested in biology.

Structure

The picture below schematically shows the structure of the plastids in the cell. Regardless of its type, it has an external and internal membrane that performs a protective function, a stroma - an analogue of the cytoplasm, a ribosome, a DNA molecule, enzymes.

In chloroplasts there are special structures - granules. The grans are formed from thylakoids - structures similar to disks. Thylakoids are involved in the synthesis of ATP and oxygen.

Starch grains are formed in chloroplasts as a result of photosynthesis.

Leukoplasts are not pigmented. They do not have tilakoids, they do not take part in photosynthesis. Most of the leukoplasts are concentrated in the stalk and root of the plant.

Chromoplasts have in their composition lipid droplets - structures containing lipids, necessary to supply the structure of plastids with additional energy.

Plastids can be of different colors, sizes and shapes. Their dimensions range from 5 to 10 μm. The form is usually oval or round, but it can be any other.

Types of plastids

Plastids can be colorless (leukoplasts), green (chloroplasts), yellow or orange (chromoplasts). It is the chloroplasts that give the leaves of plants a green color.

Another variety of plastids, chromoplasts, is responsible for yellow, red or orange coloration.

Colorless plastids in the cell serve as a storage for nutrients. Leukoplasts contain fats, starch, proteins and enzymes. When a plant needs additional energy, the starch is split into monomers - glucose.

Leukoplasts under certain conditions (under the influence of sunlight or the addition of chemicals) can turn into chloroplasts, chloroplasts are converted to chromoplasts, when chlorophyll is destroyed, and the coloring pigments of chromoplasts - carotene, anthocyan or xanthophyll - predominate in color. This transformation is noticeable in autumn, when leaves and many fruits change color due to the destruction of chlorophyll and the manifestation of chromoplast pigments.

Functions

As mentioned above, plastids can be different, and their functions in the plant cell depend on the variety.

Leukoplasts serve mainly for storage of nutrients and maintenance of vital activity of a plant due to ability to store and synthesize proteins, lipids, enzymes.

Chloroplasts play a key role in the process of photosynthesis. With the participation of chlorophyll concentrated in plastids, carbon dioxide and water molecules are converted into glucose and oxygen molecules.

Chromoplasts, due to their bright color, attract insects to pollinate plants. The study of the functions of these plastids is still ongoing.