Types of Microbodies Present in The Cells ! Biological Sciencess !!

Microbodies

These are (lysosomes, sphaerosomes, glyoxysomes and peroxisomes)

They are smallest single membrane bounded organelle. Lysosomes (suicidal bags, disposal units, scavenger of cell) are microbodies of 0.2-0.8 µ size filled with 40 types of acid hydrolases to digest (autolysis) almost every type of organic matter except
cellulose.

They are common in WBC, liver, spleen etc. They work at pH-5 and cause lysis of foreign body; discovered accidently by Christian de Duve (1955) from rat liver. Novikoff (1956) observed them under TEM. They show pleomorphism (polymorphism).

They are of four types

(i) Primary lysosomes (Storage granules) have inactive enzymes; (ii) Secondary lysosomes (Heterophagosomes or Digestive vacuoles or Phagolysosomes) cause digestion (Heterophagy); (iii) Tertiary lysosomes (Residual bodies or Telolysosomes) removes wastes by ephagy from cell by acting as scavenger or disposal unit; (iv) Autophagic vacuoles (Cytolysosome orAutophagosomes) are complex lysosomes and digest old / injured / dead cells and tissues to keep cell healthy (autolysis or autodigestion).

Scavenging, disappearance of tail, softening of gums, acrosomal activity of sperm are few other examples. Autophagy is digestion of stored food (glycogens, fat and proteins) during starvation to provide energy. Thus autophagy has no role in scavenging. If lysosomes burst and release their enzymes, the entire cell is digested and liquefied. It is called autolysis.

Osteoclasts (which digest bones) are rich in lysosomes; Plant cells lack lysosomes
except Neurospora, root tip of maize, yeast and seeds of pea and cotton.

Lack of Lysosome cause Pombe’s Disease. They are also involved with diseases such
as Tay-Sachs Syndrome and Rheumatic Arthritis (An Autoimmune disease).

Types of Microbodies

(a) Sogaerisines (Plant lysosomes) are micro bodies filled with hydrolytic enzymes for fat synthesis. They are highly refractile and rich in fat (98%) and take black stain with Sudan iii / Osmium tetraoxide. These are abundant in endosperm of oily seeds.

(b) Transosomes are triple layer bounded organelle in ovary follicle cells of birds
to help in yolk formation.

(c) Lomasomes are boder bodies between cell wall and cell membrane, common in
fungi, discovered by Moore and Mc Allister (1961) and help in cell proliferation and elongation for diffusion of substances required in cell wall formation.

(d) Peroxisomes (uricosomes) are microbodies containing enzymes for peroxide formation. Catalase and peroxidase are largest and smallest enzymes found in peroxisomes. In plants they do photo-respiration in C3 plants (Tolbert,1972). In animals they take part in lipid synthesis (b-oxidation of fatty acids).

(e) Glyoxysomes- Largest microbody of size upto 10 µ and similar to peroxisomes
as these contain catalase and other enzymes for glyoxylate cycle (a modified
Krebs’ cycle in which fats are converted into carbohydrates). These are common
in germinating oil seeds of castor, groundnut and cucumbers and disappear after germination.

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