Biology class 9 The Fundamental Unit Of Life

What is a cell?

A cell is the basic structural and functional unit of all living organisms.

When and who discovered the cell for the first time?

Robert Hooke discovered the cell for the first time in 1665.

Which cell organelle plays a crucial role in detoxifying many poisons and drugs?

The SER.

What is tonoplast?

The membrane that surrounds the Vacuole.

What is a nucleoid?

In Prokaryotes, nucleus is not bounded by a membrane and is called the nucleoid.

What is a nucleus?

It is a prominent, spherical or oval shaped structure found in Eukaryotic cells.
It is the chief controlling centre of the cell and controls all the metabolic activities taking place in the cell.

Name the cell organelle which is called the power house of the cell?

The Mitochondria.

Who gave the cell theory and who modified it?

M.J. Schleiden and Theodore Schwann proposed the cell theory which was later modified by Rudolf Virchow in 1855.

What is the cell theory?

It was proposed by Schwann and Schleiden and it states that:-
1. All living organisms are made up of cells and cellular products.
2. All cells arrive from pre-existing cells.

What are the drawback of cell theory?

Following are the drawback of cell theory:-
1. Viruses are the connecting links between living and non-living. They cannot be explained by the cell theory.
2. Bacteria and Cyanobacteria (Algae) do not have an organised nucleus.

What is the Plasma Membrane?

Each cell is enclosed by a continuous membrane, known as the Plasma Membrane. It is made up of lipids and proteins and is flexible.

What do you know about the cell wall in plants?

1. Cell wall lies outside the Plasma Membrane.
2. It is made up of Cellulose.
(Cellulose is a complex substance which gives structural strength to the plants).
3. The primary functions of the cell wall are:-
a) Protection.
b) Mechanical Support.
c) Maintenance of Balance of intracellular osmotic pressure with that of its surroundings.

What is Osmosis?

The movement of solvent molecules through a selectively/semi-permeable membrane is called Osmosis.

What is Diffusion?

The spontaneous movement of a substance from a region of higher concentration to the region of lower concentration.

Write any 5 importance of diffusion?

1. It helps in transport of substances across the cell membrane.
2. The cell walls of the internal plant tissues remain moist due to diffusion.
3. Transpiration is a diffusion process.
4. It also helps in gaseous exchange.
5. Aroma (fragrance) of flowers is diffusion of volatile aromatic compounds to attract pollinating animals.