They are minute bodies which are bounded by single unit membrane. They are formed by ER and are of three types-

Spherosomes:

They are small spherical orgenelles found in the cytoplasm of plant cells. They are bounded by single membrane of lipoprotein. They are not found in animal cells. They are formed by ER. They synthesize and store lipids. Examples – Cells of cotyledons of mustard, groundnut, sesame etc. They are also called as oleosome. They were discovered by Perner (1953). Term sphaerosome was given by Dangeard (1919). Their diameter is about 0.5 to 2.5 micron.

Peroxisomes:

They were discovered by C. de Duve (1966-67). They are round & small orgenelles which are virtually found in all eukaryotes (All plant cells, liver & kidney cells of animals). They are abundance in photosynthetic cells of plants doing photo respiration. They are full of enzymes like oxidases, catalases which function like lysosome.

Functions :

1. A major function of peroxisome is the breakdown of very long chain fatty acids.
2. The process of photo respiration occurs jointly in peroxeosomes, chloroplasts & mitochondria.
3. In animal cells, they perform fat metabolism.
4. Their catalase enzyme degrades H₂O₂ (hydrogen peroxide) released in metabolic activities.
5. They minimize the effects of toxins in the cytoplasm.

Glycoxysomes:

1. They were discovered by Harry Beevers (1961). Normally, they are found in fat rich plant cells such as fat storage tissues of germinating seeds.
2. Their enzymes initiate the breakdown of fatty acids to produce sugars (carbohydrate) by gluconeogenesis.
3. In glycoxysomes, the fatty acids are oxidized to acetyl- COA by peroxisomal p-oxidation enzymes.
4. They are absent in animal cells. They are minute orgenelles bounded by single unit membrane and perform glyoxylate cycle.