Structure and Functions
Q24. How are the vacuoles in animal and plant cells different?
Ans. Plant cell has a big central vacuole unlike a
number of small vacuoles in animal cells.
Q25. What is the function of nucleus in a cell?
in addition to its role in inheritance, acts as control centre of the activities
of the cell.
Q26. Name the animal cell which is long and has thread like
Ans. Nerve cell (a neuron) is the only animal cell
which is long and has thread like branches.
Q27. A hen’s egg can be seen easily. Is it a cell or a group of
Ans. The egg of a hen represents a single cell and is
big enough to be seen by the unaided eye.
Q28. Name one cell which can be seen by unaided eye.
Ans. Some cells are big enough to be seen with the
unaided eye. Hen’s egg is an example.
Q29. What is an organ?
Ans. An organ is a collection of different tissues
which work together to perform a particular function in the body of an
Q30. Why nerve cells are long and have branches?
Ans. Nerve cells are long and have branches so that it
can receive and transfer messages.
Q31. What regulates the movement of substances into and out of
Ans. The plasma membrane is porous and allows the
movement of substances or materials both inward and outward.
Q32. Name the smallest and largest cell in the world.
Ans. The smallest cell is 0.1 to 0.5 micrometre in
bacteria. The largest cell measuring 170 mm ×130 mm, is the egg of an ostrich.
Q33. What is cell wall? What is its
Ans. Cell wall is an additional covering over the cell
membrane in plant cells. It gives shape and rigidity to these cells.
Q34. What advantage does Amoeba derive by changing shape?
Ans. The change in shape is due to formation of
pseudopodia which facilitates movement and help in capturing food.
Q35. Name a single cell present in the human body which can
change its shape.
Ans. A white blood cell (WBC) in human blood is
another example of a single cell which can change its shape.
Q36. Name one organism which has no definite shape, and keeps on
changing its shape.
Which unicellular organism has no definite shape?
Name an organism which changes its shape frequently.
Ans. Amoeba has no definite shape, unlike other
organisms. It keeps on changing its shape.
Q37. How do scientists observe and study the living cells?
They use microscopes which magnify objects. Stains (dyes) are used to colour
parts of the cell to study the detailed structure.
Q38. What is plastid? What is the name of green plastids present
in plant cells?
Coloured bodies called plastids are found in the plant cells only. Green
plastids containing chlorophyll are called chloroplasts.
Q39. What are the three main parts of the cell?
Ans. The cell has three main parts, (i) the cell membrane,
(ii) cytoplasm which contains smaller components called organelles, and (iii) the
Q40. Name two plant organs.
– They help in the absorption of water and minerals.
– They are responsible for synthesis of food.
Q41. What are unicellular organisms? Give two examples.
Ans. The single-celled organisms are called unicellular
(uni : one; cellular : cell). Example: amoeba and paramecium.
Q42. What are pseudopodia in amoeba? What are the functions of pseudopodia?
Pseudopodia is a temporary arm-like projection. Pseudopodia facilitate
movement and help in capturing food.
Q43. What is a gene? What is its function?
Ans. Gene is a unit of inheritance in living organisms.
It controls the transfer of a hereditary characteristic from parents to