The cell is the fundamental unit of life. All living organisms on planet earth are composed unicellular (single cell) (or) multicellular (many cells). Cells range in its size from a millimeter to microns and generally varies in their shapes.Few cells are flat, oval, rod, curved, spherical, concave, rectangular, and various other shapes are also found. Most of the cells are microscopic in size and can only be seen under the microscope.
Some cells are fairly long and large. For example, a neuron in the human body is approximately 100 microns or 1 meter long and the ostrich egg is the largest cell which ranges from 14-15 cm long and 12-13 cm wide.
Animal cells are a typical eukaryotic cell with a membrane-bound nucleus with the presence of DNA inside the nucleus. They also comprise of other organelles and cellular structures which carry out specific functions necessary for the cell to function properly.
The Animal cell is smaller than the plant cell which varies in their sizes and is irregular in shape. It comprises of the following parts:
Cell Membrane: A thin semipermeable membrane layer of protein and fats surrounding the cell. It helps in owning the cell together and permits entry and exits of nutrients into the cell.
Nuclear Membrane: It is the double membrane that surrounds the nucleus.
Nucleus: A celestial body containing several organelles including the nucleolus. It contains DNA and other cell’s hereditary information.
Centrosome: It is a small organelle found near to the nucleus which has a thick center and radiating tubules. The centrosomes are where microtubules are produced.
Lysosome (Cell Vesicles): They are round organelle surrounded by a membrane comprising of digestive enzymes which help in digestion, excretion and in cell renewal process.
Cytoplasm: A jelly-like double membrane organelles found outside the cell nucleus in which the organelles are located.
Golgi Body: A flat smooth layered, sac-like organelle which is located near the nucleus and involved in manufacturing, storing, packing and transporting the particles throughout the cell.
Mitochondrion: They are spherical to rod-shaped organelles with a double membrane. They are the powerhouse of a cell as they play an important role in releasing energy.
Ribosome: They are small organelles made up of RNA-rich cytoplasmic granules and they are the sites of protein synthesis.
Vacuole: A membrane-bound organelles present inside a cell involved in maintaining shape and storing water, food, wastes, etc.
Nucleopore: They are tiny holes present in the nuclear membrane which are involved in the movement of nucleic acids and proteins within the cell.