Download CH 5 – THE FUNDAMENTAL UNIT OF LIFE

CH 5 – THE FUNDAMENTAL UNIT OF LIFE
1. Define a “cell”
Ans- A cell is defined a sthe structural unit of life or the basic unit of life.
2. White the name of the scientist and the year in which the cell was observed.
Ans – Robert Hooke in the year 1665 while observing cork, cell from the bark of the tree
with the help of a self-designed primitive microscope.
3. Draw and label the parts of a microscope.
4. Draw and label the cells of an onion peel.
5. Why do we stain an object before observing it under microscope.
Ans – By staining, the different parts of the object (cell) take up the stain at different
rates. The rte of absorption of the stain depends on the chemical components in different
parts. So by staining the different parts of the cell look differently to study it easily.
6. Draw the various cells from a human body.
7. Why is a cell called the structural and functional unit of life?
Ans – i) All living organisms are made up of cell and the cell is the smallest living unit.
ii) All the basic functions in the body of a living organisms can happen inside the
cell also.
8. Write the contribution of the following scientist in the field of Cytology.
Ans – i) Robert Hooke – Observed the cell for the first time.
ii) Leeuwenhock – Made the compound microscope and noted free living cells in
pond water.
iii) Robert Brown – Discovered the nucleus in the cell.
iv) Purkinje – Coined the term “Protoplasm” for the fluid content of the cell.
v) Schleiden and Schwann – Put forwarded the cell theory. (According to cell
theory all living organisms are made up of cells and cell is the basic unit of life).
vi) Virchow – Modified Cell theory by suggesting that a new cell arises from a
pre-existing cell.
9. Write examples for unicellular and multicellular organisms.
Ans - Unicellular – i) Amoeba
ii) Paramoecium
iii) Chlamydomonas
Multicellular – i) Plants
ii) Animals
iii) Humans
10. Different cells are differently shaped why?
Ans – The shape and size of cells are related to the specific functions they perform.
11. Name an organism without a definite shape?
Ans - Amoeba
12. A nerve cell has a typical shape. Why?
Ans - A nerve cell is engaged in doing a definite function that is transmitting messages
(impulses) electrically.
13. Define Cell Organalles.
Ans – They are definite structures inside a cell capable of doing specific functions for the
cell.
14. What are the common features of all cells?
Ans – Cell membrane or Plasma Membrane, Nucleus and Cytoplasm.
15. Draw a neatly labeled diagram of a i) prokaryotic cell ii) Animal Cell iii) Plant
Cell
16. Differentiate between Eukaryotic and Prokarijotic cell
1.They are generally small in six (1-10um)
2. Nuclear region is not well defined. So it
is called as nucleod.
3. Chromasome is single
4. Membrane - bound cell organells are
absent.
1. Size is generally large (5-100um)
2. Nuclear region is well defined and
surrounded by nuclear membrane.
3. There are more than one chromosome.
4. Membrane bound cell-organells are
present.
17. Write a short note of Plasma-Membrane.
Ans - Plasma Membrane is the outer most covering of the cell that separate the contents
of the cell from external environment. It allows the entry and exit of some materials in
and out of the cell. It prevents the movement of some materials across the membrane.
That is why it is called a selectively-permeable membrane.
18. How do molecules of different substances cross the cell membrane?
Ans- Diffusion, Osmosis, Active Transport.
19. Define Diffusion with examples.
Ans – Diffusion is the movement of molecules from a region of its higher concentration
to a region of its lower concentration.
Fg. Diffusion of oxygen and carbondioxide in the human body.
20. Define Osmosis with examples.
Ans – The movt. Of water molecules from a region of high water concentration to the
region of low water concentration through a semi-permeable membrane is called osmosis
(Diffusion of water molecules through a semi-permeable membrane).
Fg. Unicellular Fresh water organisms and plant cell gain water by osmosis. Plants
absorb water from the soil from roots also happen by osmosis.