A cell is the fundamental unit of life of any living organism. From microorganisms to humans, every living thing is made up of different types of cells. In the same vein, plants are also made up of other cells. Even though the plant cells are different in functions, locations, and structures, it has many common attributes.
Structure of Plant cell
The structure of plant cells includes various components called cell organelles enclosed by cell walls. The components of plant cells include:
Cell Wall of Plant Cell
- The cell wall is a rigid structure.
- The primary or young cell wall comprises of overlapping cellulose called microfibrils surrounded by pectin and hemicellulose. The secondary or mature cell wall is microfibrils surrounded by polysaccharides and lignin.
- It plays a vital role in providing the shape, protection, cell division, and expansion of cells.
- The cells are connected via plasmodesmata.
- Other substances present in the cell wall are resins, silica, calcium carbonate, waxes, cutin, and structural proteins and enzymes.
Cell Membrane
- A cell membrane is a semi-permeable membrane.
- It is in close contact with the cell wall and cytoplasm.
- It comprises of a variable amount of lipids and proteins that have channels within. These channels help in the movement of ions such as potassium, calcium, and hydrogen.
Cytoplasm
- The cytoplasm is a gel/liquid-like substance.
- It contains several cell organelles like Golgi bodies, endoplasmic reticulum, etc.
Nucleus of Plant Cell
- The nucleus encloses chromosomes that have DNA, the cell’s genetic material.
- It is enclosed by a double membrane having pores that allow communication with the cytoplasm.
- The chromosomes are visible only during cell division.
- Inside the nucleus, there is a specialized region called the nucleolus, where components of ribosomes are made.
Vacuole
- A mature plant consists of a large vacuole that occupies most of the space within the cell.
- The vacuole is surrounded by a single-layered membrane called the tonoplasts.
- The vacuole contains water, sugars, and various organic and inorganic salts.
- In some plants, the vacuole consists of water-soluble pigments.
- The function of the vacuole is maintaining osmotic balance, storing secondary metabolites, and regulating the turgidity of cells.
Cell organelles
The cell organelles residing in the cytoplasm and their brief description are as follows:
Endoplasmic Reticulum (ER)
- The endoplasmic reticulum consists of a network of tubes and cisternae (flattened sacs) that are enclosed by the plasma membrane.
- The ER takes up most of the cytoplasm.
- The part of cytoplasm except ER is called cytosol.
- ER functions as a transport network throughout the cell.
- There are two types of ER; Smooth ER (without any ribosomes attached) and Rough ER (with many ribosomes attached).
- Smooth ER is the site of fat, phospholipid, and hormone synthesis.
- Rough ER manufactures membrane proteins and proteins for export from the cell.
Ribosomes
- The ribosome consists of RNA and is the site of protein assembly.
- It is found in 2 places; cytosol ( freely suspending) and cytoplasm ( bounded to the endoplasmic reticulum).
Golgi bodies
- Golgi bodies or Golgi apparatus consists of a pile of membranous sacs flattened.
- A cell may have many of these sacs all interconnected. It is also connected to the membrane of ER.
- It helps in exporting proteins outside of the cell. Likewise, it modifies and transfers ER products to a specific part of the cell.
Mitochondria
- A double membrane surrounds mitochondria.
- The inner layer folds up and forms cristae which protrude inside the cavity.
- It is capable of self-replication and has DNA.
- It is the site of cellular replication.
Plastids
Plastids are of 3 types depending on the primary pigment it contains.
- Chloroplasts: The photosynthesis occurs in this plastid. It is oval in shape and is surrounded by a double membrane. Within the membrane, there is a sac-like structure called thylakoids which contain green-colored pigment chlorophyll. Other secondary pigments carotenoids and xanthophylls are also present in thylakoid. The stroma of chloroplasts consists of DNA, RNA, oil droplets, ribosomes, and other materials like scratch grains.
- Leucoplast: These are pigment less plastids that contains storage product like protein bodies, starch grains, and oils. Leucoplast that contains starch grains is called amyloplast.
- Chromoplast: This colorful plastid has pigments like red, yellow, and orange. It is usually present in the fruits and flowers of the plant.
Reference
- Glimn-Lacy, J., & Kaufman, P. (2006). Botany illustrated (2nd ed., pp. 1-3). Springer.
- ESSENTIAL PLANT BIOLOGY. Myerscough.ac.uk. (2013). Retrieved 9 May 2022, from https://www.myerscough.ac.uk/media/3751/plant-cells-and-anatomy-session-booklet.pdf.
