CBSE Board - Class VIII, NCERT Science
Chapter 8, Cell - Structure and Functions
Ncert Solutions and Answers of Science Textbook Important Exercise Questions
Question.1: Indicate True(T) or False(F)
a. Unicellular organisms have one-celled body.
b. Muscle cells are branched structures.
c. The basic living structure of an organism is an organ.
d. Amoeba has irregular shape.
Answer: a)T b)T (spindle shaped structures) c)F d)T.
Question.2: Make a sketch of the human nerve dell. What function do nerve cells perform?
Answer: Functions of human nerve cell:
- Nerve cells receive message from different parts of body.
- They further transfer these messages to brain and accordingly brain send commands for functioning of different organs of body.
Question.3: Write short notes on the following:
(a) Cytoplasm (b) Nucleus of a cell
(a Cytoplasm: Cytoplasm is a jelly like substance which is present between the cell membrane and the nucleus. Various other organelles of cells are present in the cytoplasm. Cytoplasm is made up of chemical substances like carbohydrates, proteins and water. These chemical substances are present in cells of all types and sizes. Cytoplasm contains many important tiny substances called Organelles.
(b Nucleus of a cell: Nucleus is the master of the cell. It commands all the functioning of the cell. It is generally located in the center of the cell and is spherical in shape. A membrane called nuclear membrane separates it from cytoplasm. It contains the genetic material DNA and RNA in it. This porous membrane allows the transfer of material in the nucleus and cytoplasm. Nucleus contains a dense body called Nucleolus which actually contains Chromosomes, the genetic material.
Question.4: Which part of the cell contains organelles?
Question.5: Make sketches of animal and plant cells. State three differences between them.
Answer: See answer of Q.No.6 (Extra study materials additional long type questions - Link given below).
Question.6: State a difference between eukaryotes and prokaryotes.
Answer: Prokaryotes do not have a well designed nuclear membrane while, eukaryotes have a well designed nuclear membrane.
Question.7: Where are the chromosomes found in cell? State their functions.
Answer: Chromosomes are found in the nucleus of a cell. Their function is to carry characteristic features of parent cells to the daughter cell means, from parent to offspring.
Question.8: ‘Cells are the basic structural units of living organism’. Explain.
Answer: In Biology, the basic unit of which all living things are composed is known as ‘cell’. The ‘cell’ is the smallest structural unit of living matter that is capable of functioning independently. A single cell can be a complete organism in itself, as in bacteria and protozoans. A unicellular organism also captures and digests food, respires, excretes, grows, and reproduces. Similar functions in multi-cellular organisms are carried out by groups of specialized cells which are organized into tissues and organs such as, the higher plants and animals. Hence, ‘cell’ is known as the basic structural and functional unit of life.
Question.9: Explain why chloroplasts are found only in plant cells.
Answer: Chloroplasts are found only in plant cells because they are required for photosynthesis.
Extra Study Materials