Cell Structure

  

A cell is the smallest working unit of all living organisms on our planet earth, which is capable of performing life functioning. Hence it can also be defined as a fundamental unit of life. The term cell was first observed and identified by an English physicist Robert Hook in the year 1665.There were many theories developed for cell. Later in the year 1839 a two German scientist – Schwann and Schleiden provided few basic principles of cell.

Cell Structures

There are many cells in an individual, which performs several functions throughout the life. The different types of cell include- prokaryotic cell, plant and animal cell.  The size and the shape of the cell range from millimeter to microns, which are generally based on the type of function that it performs. A cell generally varies in their shapes. A few cells are in spherical, rod, flat, concave, curved, rectangular, oval and etc. These cells can only be seen under microscope.

Cell Theory

• Every living organism is made up of a single cell (unicellular) (or) many cells (multicellular) and all types of cells have certain structures in common like: genetic material and plasma membrane.
• Cell is the smallest living thing.
• Each cell arises only from pre-existing cells.

• Cell Structure and Function

  Cell wall: It helps in protecting the plasma membrane and plays a vital role in supporting and protecting the cells.    It is a thick outer layer made of cellulose. 
  
  
  Cell membrane: It is a double layered, thin barrier, surrounding the cell to control the entry and exit of certain substances.
  
  
  Cytoplasm: It is a membrane, which protects the cell by keeping the cell organelles separate from each other. This helps to keep a cell in stable. Cytoplasm is the site, where many vital biochemical reactions take place.
  Nucleus: They are the membrane bound organelles, which are found in all eukaryotic cells. It is the very important organelle of a cell as it controls the complete activity of a cell and also plays a vital role in reproduction.
  
  
  Nuclear membrane: The bilayer membrane, which protects the nucleus by surrounding around it and acts as a barrier between the cell nucleus and other organs of a cell.
  
  
  Nucleolus: It is an important membrane found inside the nucleus. It plays a vital role in the production of cell's ribosome.
  
  
  Chromosomes: It is made up of DNA and stored in the nucleus, which contains the instructions for traits and characteristics. 
  
  
  Endoplasmic reticulum: It helps in the movement of materials around the cell. It contains an enzyme that helps in building molecules and in manufacturing of proteins. The main function of this organelle is storage and secretion. 
  
  
  Ribosome: It plays a vital role in protein synthesis.
  Mitochondria: They are double membrane, filamentous organelles, which play a vital role in generating and transforming the energy. Mitochondria play a vital role in various functions of the cell metabolisms including oxidative phosphorylation.
  
  
  Golgi Bodies: It helps in the movement of materials within the cell.
  
  
  Lysosomes: It is also called as suicidal bags as it helps in cell renewal and break down old cell parts.
  
  
  Vacuoles: It helps plants in maintaining its shape and it also stores water, food, wastes, etc.
  
  
  Chloroplast: They are the site of photosynthesis, which are present in chlorophyll bacteria, blue-green algae, etc