Cell 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?

Ans. Nucleus, 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 branches.

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 cells?

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 organism.

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 the cell?

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 function?

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.
Or
Which unicellular organism has no definite shape?
Or
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?

Ans. 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?

Ans. 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 nucleus.

Q40. Name two plant organs.

Ans. Roots – They help in the absorption of water and minerals.

Leaves – 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?

Ans. 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 offspring.