Questions & Answers

Which is not true about spherosomes?
A. Arise from E.R
B. Related to fat
C. Single membrane bound structure
D. Involved in photorespiration

Answer Verified Verified
Option A is incorrect. Spherosomes are membrane-covered spherical organelles that derive from endoplasmic reticulum and are surrounded by a single yet half-unit membrane with a monolayer of phospholipids with polar heads to the cytosol and hydrophobic tails to the inside. Proteins called oleosins stabilize their membrane.
Option B is incorrect. Spherosomes or oleosomes are small cellular organelles found in single-membrane plant cells. It is primarily responsible for storing and synthesizing (lipid) fats. In spherosomes, the lipid content is 98% and the protein content is only 2%.
Option C is incorrect. Perner (1953) discovered Spherosomes are small membrane bound organelles that participate in fat storage and synthesis. They have granular content, rich in lipids but also some proteins. They are formed by endoplasmic reticulum. Spherosomes have lysosomal activity in some plants, e.g. maize root tip.
Option D is correct. Photorespiration or also known as C2 cycle is a phenomenon involving the removal of fixed carbon when light is present in plants such as CO$_2$. It begins in chloroplast, but does happen in peroxisomes. It is a wasteful process since the mechanism of using light energy in photosynthetic species to fix carbon for subsequent carbohydrate synthesis represents a significant loss. Oxygen fixation during photorespiration is done by RuBiSCO, the enzyme which fixes carbon dioxide during the Calvin cycle.

So, the correct answer is Option D.

Note: As photorespiration is an inefficient process that occurs when the RuBiSCO Calvin cycle enzyme acts on oxygen and not carbon dioxide. Plants including Crassulacean acid metabolism (CAM) reduce photorespiration and conserve water by distinguishing these steps between night and day in time.