Question

An outer covering membrane is absent over
A. Nucleolus
B. Lysosome
C. Mitochondrion
D. Plastid

Answer 1

Hint: Eukaryotes have membrane bound nucleus. Nucleolus is not present in the cytoplasm of the cell; it is present in the nucleoplasm of the nucleus. Every organelle of the cell is membrane bound. Lysosome, mitochondria and plastid all are membrane bound organelles of the cell. They perform important functions of the cell.

Complete answer:
The basic structural and functional unit of life is termed as a cell. Various organelles are present in the cell which performs different functions. Eukaryotes have membrane bound nucleus and other organelles. Prokaryotes do not have membrane bound nuclei. Nucleolus is present inside the nucleus of the cell which is a small, dense, spherical structure and lacks a membrane. Nucleolus is visible during the interphase of the cell division under the microscope. Nucleolus helps in synthesis of r-RNA and ribosomes. Nucleolus has specific chromosomal regions in which proteins, DNA and RNA are formed. These regions are also called as nuclear organizing regions.
Lysosomes perform various functions in cell processes. They are membrane bound organelles and they also have digestive enzymes that help in various cell processes. Another name given to the lysosomes is suicidal bags. Various bacteria and viruses may be destroyed in it.
Mitochondria are the powerhouse of the cell. It is a membrane bound cell organelles. They are found in the cytoplasm of the cell. Energy produced by mitochondria is adenosine triphosphate (ATP). Multiple mitochondria can be found in cells depending on their function.
Plastid is a membrane bound organelles found in the cells of plants, algae, and some other eukaryotic organisms.
From the above information we can say that nucleolus does not contain any outer covering membrane.

Therefore, the correct answer is option A.

Note: All living beings are made up of cells. Cells are mainly made up of protein and organelles. Animal cells have an outer membrane known as cell membrane or plasma membrane. Plant cells have cell walls. Cells have many organelles such as, endoplasmic reticulum, Golgi bodies, vacuole, ribosomes etc. Every organelle has a different set of functions. Motor neuron is the longest cell of the human body.