The micro bodies (tiny but important):

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These are small sac-like structures bounded by their membranes. These are of different kinds of which we will take up three like lysosomes, peroxisomes and glyoxysomes.

Lysosomes (Lysis = Breaking down; Soma = Body):

Lysosomes are membrane bound sacs filled with digestive enzymes. Lysosomes are present in almost all animal cells and some non-green plant cells. Lysosomes may be hundreds in single cell and contain several enzymes. Lysosomes digest any foreign material as well as worm-out cell organelles and hence, keep the cell clean of any unwanted waste material. In case of cell gets damaged, lysosomes burst and release the enzyme, which digests their own cell. Hence they are called suicide bags of the cell.

Functions: Lysosomes helps in intracellular digestion, provide energy during starvation by controlled breakdown of stored food. Lysosomes bring about cellular breakdown and are associated with ageing.

Image showing Digestion by lysosomes.

Image Showing Digestion by Lysosomes.

Image showing Digestion by lysosomes.

Importance of intracellular digestion by the lysosomes: help in nutrition of the cell by digesting food, as they are rich in various enzymes which enable them to digest almost all major chemical constituents of the living cell. Help in cleaning up the cell by digesting damaged material of the cell. Provide energy during cell starvation by digestion of the cells own parts.

Peroxisomes:

They are found both in plant and animal cells. They participate in oxidation of substrates resulting in the formation of hydrogen peroxide. They often have a crystalline structure within an amorphous matrix. They are round or oval vesicles surrounded by a phospholipid bilayer. They are self-replicating. Peroxisomes are abundant in the liver where they produce bile salts and cholesterol and break down fats. Peroxisomes contain more than 50 enzymes. They are usually closely associated with E.R.

Functions: -oxidation of fatty acids, glyoxylate cycle, photorespiration (Glycolate pathway), Degradation of purines, Decomposition of hydrogen peroxide.

Glyoxysomes:

The micro bodies are present in plant cells and morphologically similar to peroxisomes. They are found in the cell of yeast and certain fungi and oil rich seeds in plants. They contain enzymes of fatty acid metabolism involved in the conversion of lipids to carbohydrates during germination.

Cilia and Flagella (The Organelles for Mobility):

Cilia and flagella are tube-like appendages which allow for motion in eukaryotic cells. If a cell has a single appendage, which often looks tail-like, it is called a flagellum, but if it has many, they are called cilia. The motion of the cilia or flagellum moves the liquid outside the cell and if the cell is not anchored, it can swim. Cilia and flagella are situated external to cytoplasm but have their origin from cytoplasm. Both are made up of contractile protein tubulin in the form of microtubules. The arrangement of the microtubules in termed 9 + 2, that is, two central microtubules and nine set surrounding them.

Image Showing Difference between Cilia and Flagella.
Image showing difference between cilia and flagella.

Cilia

Flagella

shorter (5 to 10 m)

longer (15 m)

several 100 per cell structure : protoplasmic

projection and membrane bound

usually 1 or 2 in most cells

consist of 9 sets of peripheral microtubules and 1 set of tubules in the centre

same as in cilia

Image showing difference between the movement of cilia and flagella.

Difference between the Movement of Cilia and Flagella.

Image showing difference between the movement of cilia and flagella.

Centriole:

Centriole is the one of a pair of small cylindrical cell organelles near the nucleus in animal cells; composed of nine triplet microtubules and form the asters during mitosis. It is cylindrical, 0.5 µm in length and without a membrane. It has its own DNA and RNA and therefore it is self-duplicating.

Image showing centriole structure.

Image Showing Centriole Structure.

Image showing centriole structure.

Functions: Centrioles are involved in cell division. They give orientation to the mitotic spindle which forms during cell division.

Basal Bodies:

These are structures similar to centrioles. They have the same nine sets of triplet organization, as in the centrioles. The cilia and flagella appear to arise from the basal bodies.