Question

..................is called the living substance of a cell.
A. Protoplasm
B. Cytoplasm
C. Cell membrane
D. Cell wall

Answer 1

Hint: The cytoplasm, nucleus and the cell organelles are enclosed within the cell membrane.

Complete Answer:
Protoplasm is called the living substance of the cell. The entire content of a living cell is known as protoplasm. It includes the cytoplasm and the nucleus.
Protoplasm = Cytoplasm + Nucleus

Components of Protoplasm:
1. Cytoplasm: The first component of the protoplasm is cytoplasm. It is the gel-like substance present in between the cell membrane or plasma membrane and the nucleus.
- In eukaryotes (cells with nucleus), cell organelles are found suspended in the cytoplasm.
- These are endoplasmic reticulum, ribosomes, golgi apparatus, lysosomes, mitochondria etc. - Cytoplasm plays an important role in maintaining the shape of a cell. Most of the important chemical reactions of the cell take place in cytoplasm.

2. Nucleus: The second component of the protoplasm is nucleus. The nucleus is a large spherical structure and located in the centre of the cell. It is called the control center of the cell.
- Nucleus is separated from the cytoplasm by a nuclear envelope, formed by two nuclear membranes. The nuclear envelope is porous and contains many nuclear pores. It encloses the liquid ground substance called nucleoplasm.
- Nucleolus and chromatin materials are suspended in the nucleoplasm. Nucleus play an important role in transmission of hereditary characters from the parents to the offspring. If the nucleus is removed from a cell, the protoplasm dries up and ultimately dies.

Note: Protoplasm consists of macromolecules such as ions, amino acids, water & monosaccharides and macromolecules like nucleic acids, proteins, lipids and polysaccharides.