Structure of the cell

  Structure of the cell 

The cell is the basic structural and functional unit of life. Cells are considered as building blocks of complex multicellular organisms because it plays the same role in the formation of the body as bricks play in the construction of the building. Almost all organisms present on earth today are made up of cells. They may be unicellular containing only one cell e.g. bacteria or multicellular organisms consist of many cells e.g. animal cells.

Components of Cell

The structure of a cell contains a variety of components. The cell consists of an outer cell membrane in the case of an animal cell while plant cells and many prokaryotic cells such as bacteria also contain cell wall outside the cell membrane. 

 The cell membrane is made up of a lipid bilayer along with embedded protein. It acts as a semipermeable membrane allowing some substance to pass through it while hampers the others. 

The cytoplasm consists of aqueous ground substance present within the cell which comprises a variety of cell organelles such as the nucleus, mitochondria, ribosomes, Golgi complex,  endoplasmic reticulum, plastids, vacuoles, cytoskeleton, centrioles, and lysosomes. The cytoplasm is the site for a variety of metabolic reactions. There is a division of labor among these organelles.  The nucleus occupies the central space in the case of an animal cell while it is pushed towards the periphery due to the presence of a large vacuole in the center of plant cells. 

The nucleus controls almost all the activities occurring within the cells. A mitochondrion is also a very important organelle that involves in the cellular respiration and energy (ATP) production for organisms. It is considered as a powerhouse of cells. Ribosomes make protein according to the instruction given by the nucleus. These proteins may be an enzyme, hormones or any other stuff which play a very vital role within the cells or outside the cells. Therefore this protein is packed in the sacs made in the endoplasmic reticulum and modified by the Golgi complex to transport it within the cell or outside the cells to perform their function. The lysosome is an organelle that contains digestive enzymes for the digestion of food. Plastid is an organelle that presents only in plant cells. It has three types i.e. chloroplast, chromoplast, and leucoplast. Chloroplast involves photosynthesis while chromoplast helps in the pollination and leucoplast has its role in the storage of food. Vacuoles are the sites for the storage of water and other metabolic products. It also gives turgidity to the plant cells.  Cytoskeleton gives shape to the cells and involves in the assimilation of cellular compartments. Centrioles involve in the formation of spindle fibers during cell division. Besides this many other organelles are present within the cell according to the specificity of cells.

Division of labor

Cells are considered the smallest unit of life because cells are the smallest components of living things. It can perform all the activities of living organisms. Cells can do all the work on their own due to the division of labor among the organelles. In the case of multicellular organisms, there is a division of labor among the cells. The function of an organism as a whole is the result of the sum of activities and interaction of different cells and of different components of the cell. For example muscle cells contract and relax, nerve cells transmit impulses, gland cells secret, and red blood cells carry oxygen. In this way, all the activities of an organism are the sum of functions of a variety of cells in multicellular organisms.