Cells are the building blocks of all living organisms. It is the structural and functional working unit of life. Therefore it is also described as the fundamental unit of life. The term cell was first identified in the year 1665 by an English philosopher Robert Hooke and later in the year 1839, German scientists – Schwann and Schleiden presented basic principles and theories of the cell.
The cell structure varies in their shape, and size, it is mainly depended on their functions. There are several cells involved in performing different functions throughout the life. Prokaryotic and eukaryotic are two types of cell which are classified based on the presence or absence of a true nucleus. The shape and size of the cells vary based on the type of function it performs. In general, the cells are curved, spherical, rod, concave, flat, rectangular, oval and it can be clearly examined only under the electric microscope.
Eukaryotic cells are those cells which contain a true nucleus and are found only in all multicellular organisms. Both plant and animal cell are examples of Eukaryotic cells.
Prokaryotic cells are the cells without the nucleus. Bacteria and other unicellular organisms are examples of Prokaryotic cells.
Functions of Cell Organelles
Every cell structure has some specific functions. Here we would discuss the functions of the different cell organelles.
Cytoplasm is a primary component of the cell where all the cell structures are embedded within it. It is a jelly-like liquid component that combines the cell membrane and the nucleus. Most of the chemical reactions within a cell take place in this cytoplasm. Other cell organelles including endoplasmic reticulum, vacuoles, mitochondria, ribosomes, are all suspended in this cytoplasm.
- Plasma Membrane
Every cell has three basic components namely plasma membrane, nucleus, and cytoplasm. Among these, the plasma membrane is the outer covering of a cell within which all other organelles including cytoplasm and nucleus are enclosed. It is also referred to as the cell membrane. By structure, it is a porous membrane (with pores) which permit the movement of selective substances in and out of the cell. Besides this, cell membrane also protects the cellular component from damage and leakage. It forms the wall like structure between two cells as well as between the cell and its surroundings.
Plants are special, so are their cell structures. Since plants are immobile and cannot hide or run away as animals do during the atmospheric changes. Plants have an advanced cell structure that protects them and makes them rigid and is called a cell wall. The cell wall is a thick outer layer and is present only in plants cell which protects the plasma membrane and other cellular components. The cell wall is the outermost layer of plant cells.
The nucleus is the most prominent and largest organelle of the cell. It is present in all eukaryotic cells except in few cells of mammalian RBCs. The word nucleus is derived from a Latin word meaning ‘kernel’. It is a double-membrane bound cell organelle comprising most of the genetic material of the cell – the DNA. The shape of the nucleus is mostly round, oval, or disc-shaped depending on the type of cell. It occupies about 10% of the total cell volume.
The primary function of the nucleus is to create an identical copy of the DNA by replication. It is responsible for cell division, protein synthesis, controlling the heredity characteristics, growth and differentiation of an organism. It is known as the control center of the cell as it is responsible for regulating gene expression, cell’s growth, reproduction and other activities of the cell.
Ribosomes are a small, minute particles consisting of associated proteins and RNA found within the cytoplasm of a cell. They are the protein factories of the cell and are mainly involved in protein synthesize. They are found floating within the cytoplasm both in plants and animals cell.
- Endoplasmic reticulum
The endoplasmic reticulum is the network of membranous tubules which are mainly involved in the synthesis of protein and lipids and transport of cellular materials. Rough endoplasmic reticulum is involved in protein manufacture and the smooth endoplasmic reticulum serves to produce vital lipids (fats).
- Golgi apparatus
Golgi apparatus are complex of vesicles with a series of flattened membranes. They are sac-like structures found both in plant and animal cells. They are mainly involved in the sorting, modification, packaging of proteins for secretion and also in the transportation of lipids around the cell.
Chloroplasts are the specialized organelles, bounded by a double membrane layer which are found only in plants and some algae. The main role of chloroplasts is to conduct photosynthesis by capturing the solar energy to transform water and carbon dioxide into glucose. These chloroplasts consist of green color pigments called chlorophyll which play a primary role in the photosynthesis process.
They are called as the powerhouse of the cells as they produce energy through cellular respiration. Apart from production of energy, mitochondria are also involved in Processing and storage of calcium ions, in Regulation of cellular metabolism, in the process of cell Apoptosis, etc.
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