Digestion in unicellular organisms.

     DIGESTION IN UNICELLULSR ORGSNISMS…..

           Probably digestion is quite a common word which we hear and use mostly but what does it mean? Or what is digestion?

    So digestion is a chemical process during which large molecules (polymer) are broken down into relatively smaller molecules which can be easily absorbed and used by our body.

            When we take food, our food contains four polymers carbohydrates, protein, lipids or fats and nucleic acids. We take food to get energy after their catabolism, from which we carry own different activities of life such as movement, support, reproduction, etc. In order to use these molecules our body must digest it before it could use. Therefore our body digest carbohydrates into glucose, proteins into amino acid and dipeptides, lipids into glycerol and fatty acids. In the same way micro organisms or unicellular heterotrophic organisms must digest their food as we human do before they could use. They digest their food in a different way so how do they digest their food?                   

  

            INGESTION :

            Cells engulf the food through endocytosis as shown in the figure. This process of taking in the food is called ingestion. The cells take in the food by vacuole formation as the cell rips the food and small amount of water by cell membrane. The structure which is now present in the cell is called food vacuole.

                

            DIGESTION :

           As the food vacuole is formed inside the cell, an organelle named LYSOSOME comes near the food vacuole and secret its enzymes on the food vacuole. The secretions released by the lysozyme includes hydrolytic enzymes which digest the food inside the food in the food vacuole.

The digested food diffuses through the membrane into cytoplasm and after some time when the whole food is digested, the waste materials are ejected out of the cell through exocytosis.

          Exocytosis is the process during which when materials are thrown out of the cell. It is something different from diffusion and the process of exocytosis includes when membrane bounded compartment of the cell touches the cell membrane then the process of expelling occurs immediately. This is shown in the following figure below….

               

            ASSIMELATION:

       Assimilation is the usage of the digested food for the cell. It includes not only the cellular respiration but also cellular growth and protein synthesis. The digested food contains monosaccharides (glucose) from carbohydrates, amino acids from protein and mono, di and tri glycerides from fats or lipids.