Science [ 2 Marks Questions ]

Robert hooke was a scientist and inventor. He improved the microscope and built a compound microscope. One day he made thin sections of the cork and observed many small identical chambers through his microscope. They were hexagonal in shape. Based on these observations Hooke published a book named Micrographia in the year 1665, where he first used the term Cell. He describes the structure of tissue using the term cell.

A brick is a basic building block of a wall, likewise, the cells are the basic structural and functional unit of every living organism. So the cells are called building blocks of life.

No, the big onion and small onion both of them have plant cell and the size of every cell remains same whether it is of a small onion or big one. The shape is larger means that the number of cells is more in bigger onion.

Structure of Nucleus
A – Nuclear membrane
B – Nuclear pore
C – Nucleolus
D – Chromatin reticulum

A – Outer Membrane
B – Cristae
C – Matrix

The diagram is the structure of the chloroplast
A – outer membrane
B – inner membrane
C – Thylakoid
D – stroma

Ribosomes are the cell organelle in which the membrane is absent.

The largest Angiosperm cell is citrus reticulata (clearly visible in orange pulp) & citrus maxima.

Living cells have a nucleus (Eg.) Onion peel cells.
Non-Living cells don’t have a nucleus (Eg.) Cork ceils.

(a) Bacterial cell
(b) Human egg
(c) Frogs egg
(d) Hen’s egg