Question

Membrane is absent in
A. Nucleus
B. Nucleolus
C. Vacuole
D. Lysosome

Answer 1

Hint: Two types of cells are present: prokaryotic and eukaryotic cells. The nucleus is not membrane-bound in case of prokaryotes and other membrane-bound organelles are also absent, whereas, in eukaryotes, the nucleus has an envelope with numerous pores in it.

Complete answer:
Eukaryotic cell has a true nucleus, membrane-bound organelles and rod-shaped chromosomes. The nucleus of the cell is surrounded by a nuclear membrane. Nuclear membrane constitutes two layers. Both the layers are made up of phospholipids. The nuclear pore is present in the nuclear envelope which facilitates in the exchange of ions, RNA and molecules from the nucleus and cytoplasm. Inside the nucleus, is the nucleoplasm and the genetic material called DNA. The nucleolus is present in the nucleoplasm and it is composed of RNA and proteins. It is a non-membrane-bound structure that performs the function of assembling and synthesis of RNA and proteins.
i. Several membrane-bound organelles are present in eukaryotes such as
mitochondria, which is the powerhouse of the cell as it is responsible for the production of ATP by conducting cellular respiration.
ii. Two types of endoplasmic reticulum namely rough endoplasmic reticulum having ribosomes on their surface; they perform the function of protein synthesis and smooth endoplasmic reticulum without ribosomes that perform the function of lipid synthesis
iii. Golgi apparatus is involved in packaging and transporting of proteins and lipids.
iv. Vacuoles are membrane-bound sacs which perform the function of storage.
v. Lysosomes are also membrane-bound and contain several digestive enzymes and perform the function of removing dead and foreign bodies.
Hence, the correct answer is option (B).

Note: Cell is the structural and functional unit of life. It contains the genetic material which is passed from one generation to the next. Cell follows two types of cell division, i.e. mitosis and meiosis. Mitosis occurs in somatic cells, whereas, meiosis occurs in germ cells.