Plant cells are eukaryotic cells having a true nucleus and specialised structures termed organelles, both of which perform specific roles essential for the survival of the cell.
- They are generally larger and rectangular than animal cells.
- They are different from animal cells while having certain cell organelles in common.
Structure of a Plant Cell
A Plant cell is a basic structural and fundamental unit of a plant. A plant cell is eukaryotic, just like an animal cell, which means it has a membrane-bound true nucleus and organelles that perform specific functions. It prepares its own food through photosynthesis. The structure of a plant cell is composed of the following parts:
1. Cell Wall
- The outermost rigid layer of a plant cell.
- Animal cells lack this.
- The main role of a cell wall is to give the cell rigidity and support against mechanical stress, and also allow for the circulation of water and minerals into and out of the cell.
2. Cell Membrane
- Every cell has this semi-permeable membrane, whether it be an animal or a plant cell.
- A cell membrane acts as a barrier between the external environment and the inside protoplasm of the cell.
- It permits the entry and exit of certain substances through highly regulated channels.
3. Nucleus
- In eukaryotic cells, the nucleus is a membrane-based vital organelle.
- The nuclear envelope surrounds the nucleus like a shell. The nucleus has two parts: the Nucleolus and Nucleopore.
- Nucleolus: It helps in the synthesis of ribosomes and protein manufacturing structures.
- Nucleopore: The holes in the membrane of a nucleus are called the nucleopores, and these allow proteins and nucleic acids to flow through.
4. Plastids
- Algae and plant cells have double-membrane-bound organelles called plastids.
- There are three types of Plastids: Chloroplasts, Leucoplasts, and Chromoplasts.
- Chloroplasts are a type of plastid that are involved in photosynthesis.
- Chromoplasts store pigments such as carotenoids.
- The leucoplasts are present in non-photosynthetic tissues of plants and store proteins, starches, and oils.
5. Central Vacuole
- This is the largest organelle present in plant cells.
- It is bounded by a membrane known as the Tonoplast.
- Vacuoles perform roles like waste disposal, storage, and maintenance of turgor pressure in a cell.
6. Golgi Apparatus
- They are mainly responsible for distributing synthesised macromolecules to the various parts of the cell.
- It consists of several flattened, stacked pouches known as Cisternae.
7. Ribosomes
- They are also known as the “Protein factories of the cell”.
- It is a macromolecular machine that synthesises biological proteins.
- They are flattened and spherical in shape and are comprised of two major components: the large and small ribosomal subunits.
8. Mitochondria
- Mitochondria are also known as the “powerhouse of the cell”.
- These are the double-membrane-bound organelles that produce energy by breaking down sugar and carb molecules.
- They vary in shape, ranging from oval to tubular-shaped, double-membrane organelles.
9. Endoplasmic Reticulum
- The portion of the ER that is attached to the ribosomes is known as the rough ER.
- They are primarily responsible for the synthesis of proteins within the cell.
- When compared to rough ER, the smooth ER appears smoother because it does not have ribosomes on its surface.
- They play a very crucial role in the synthesis of lipids, the metabolism of carbohydrates, and the detoxification of drugs.