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.
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