These AP 8th Class Biology Important Questions and 1st Lesson Cell Structure and Functions Class 8 Extra Questions will help students prepare well for the exams.
Class 8 Science Cell Structure and Functions Extra Questions
Cell Structure and Functions Class 8 Important Questions
Question 1.
Who discovered cell first time ?
Answer:
It was the year 1665 Robert Hooke, a British scientist discovered the cell.
Question 2.
Which part of cell contains cell organelles ?
Answer:
The jelly like substance between the nucleus and cell membrane is called cytoplasm. It is a heterogeneous material. It contains membrane bound structures called cell organelles.
Question 3.
Make different questions to know cells and cell organelles.
Answer:
- What are the structures present in the cells ?
- Why cells are considered to be structural and functional unit of life ?
Question 4.
What are unicellular organisms ? Give examples.
Answer:
The organisms survive its life with a single cell are called unicellular organisms.
Ex : Amoeba, Paramecium, Chlamydomonas, etc.
Question 5.
What is the meaning of ‘Cell’ in Latin ?
Answer:
In Latin ‘cell’ means ‘A little room’.
Question 6.
What is the basic structural unit of all living organisms ?
Answer:
Cell.
Question 7.
Which organism has the smallest cell ?
Answer:
Bacteria (Mycoplasma)
Question 8.
Name the cells that are branched, in our body.
Answer:
Nerve cell
Question 9.
What are the locomotory organs of Amoeba ? ‘
Answer:
Pseudopodia.
Question 10.
What is responsible for the size of the organism ?
Answer:
The size of the organism depends on the number of cells and not on the size of the cell.
Question 11.
What is the shape of amoeba ?
Answer:
Amoeba has no definite shape. It continuously changing its shape by producing pseudopodia. Hence, it looks irregular in shape.
Question 12.
What is the function of cell wall ?
Answer:
- It provides rigidity to the plant cell.
- It gives mechanical strength to the plant cell and protects it against variations in temperature, wind speed and humidity.
- It gives shape to the cell.
Question 13.
Name the instrument that is used to observe microscopic structures in living bodies.
Answer:
Microscope.
Question 14.
Give examples for multicellular organisms.
Answer:
Snake, Hydra, Earthworm, Man, Mango tree etc.,…
Question 15.
Write the names of different stains used to observe cells under microscope.
Answer:
Methylene blue and saffranine.
Cell Structure and Functions Extra Questions
Question 1.
What is the significance of cover slip in your preparation of slides ?
Answer:
- Cover slip protects the material under study from coming in contact with the lens of the microscope.
- It presses upon the material keeping it plane.
Question 2.
How do you appreciate the role of microscope in the study of cell ?
Answer:
- The microscope is very useful instrument in the study of cells.
- Scientists use electron microscope for their study which can help to see upto a millionth of a meter.
- I will appreciate the role of microscope in the growth and development of science and human welfare.
Question 3.
Name the cell organelle and pigment that is responsible for green colour.
Answer:
- Chloroplast is the-cell organelle that is present in leaves.
- It contains a pigment called “Chlorophyll”, which gives green colour to the leaves.
Question 4.
What is the difference between protoplasm and cytoplasm ?
Answer:
- Protoplasm is the liquid substance enclosed by cell membrane.
- Cytoplasm is the liquid between the nucleus and plasma membrane. The cell organelles appear as small particles in cytoplasm.
Question 5.
Draw a labelled diagram of amoeba.
Answer:
Question 6.
Name the factors on which shape of the cells depend.
Answer:
The shape and size of the cells vary considerable but all of these cells ultimately determined by the specific function of the cells.
e.g. : Amoeba is changing its shape for specific functions like collection of food and locomotion.
The shape of the cell may vary for giving definite structure to the organism, e.g.: Epidermal cells.
Question 7.
If you want to know about unicellular and multicellular organisms, what questions will you pose ?
Answer:
- What do you mean by unicellular organism ?
- What do you mean by multicellular organism ?
- Give examples for unicellular and multicellular organisms.
- What are the diffeences between unicellular and multicellular organism ?
Question 8.
Deepak said, “A plant can’t stand erect without cell wall”. Support this statement.
Answer:
Deepak said, “A plant can’t stand erect without cell wall.” We support this statement with the following reasons.
- Plant cells differ from those of animals in having an additional layer around the cell membrane.
- We called if as ‘cell wall’.
- Cell wall gives strength and rigidity to plants.
So a plant can’t stand erect without cell wall.
Question 9.
What would happen to the different functions carried out by the human body if all the cells in human body have identical structure ?
Answer:
- In human body, different cells exhibiting different functions have different structures. Ex : RBC are round and nerve cells are long and branched.
- If nerve cells are round like RBC they may not transfer messages to longer distance in the body.
- If all the cells are identical in structure, they cannot carry their functions normally.
Question 10.
Write the difference between White Blood Cell and Amoeba.
Answer:
A White Blood Cell (W.B.C) in human blood is a single cell which can change it’s shape. But White Blood Cell is a cell.
Amoeba is a full pledged organism capable of independent existence.
Question 11.
“Cells are the building blocks of life”. Explain.
Answer:
All living organisms are made up of cells. All the life processes take place inside the cell. Many similar cells combine together form into tissues. Tissues organise to form into organ. Many organs organise to form organ systems. Many organ systems together form into an organism. So cells are known as building blocks of life.
Question 12.
Cells consists of many organelles, yet we do not call any of these organelles as structural and functional unit of living organisms. Explain.
Answer:
- Various other components or organelles are present in the cytoplasm. These are mitochondria, golgi bodies, ribosomes, lysosomes, vacuoles, etc.
- Although cell organelles have specific functions and perform specific functions but they cannot be called structural and functional units of living organisms.
- Because they can perform their functions only when they are within the living cell. They cannot function outside the cell as an unindependent unit.
Question 13.
What is protoplasm ? How does it have living nature ?
Answer:
- Protoplasm is a fluid viscous substance of the cell and is surrounded by a membrane called plasma membrane.
- It contains different components such as water, carbohydrates, proteins, nucleic acid and mineral salts.
- These components in special combination provide living nature to protoplasm.
Question 14.
What is gene ? What is it’s function ?
Answer:
Nucleus contains thread like structures called Chromosomes. These carry Genes which is the segment of DNA.
Function of gene : Genes help in transfer of hereditary characters from parents to offsprings.
Question 15.
How is the cell discovered by the scientists in the beginning ?
Answer:
- In 1665 Robert Hooke observed slices of cork under a simple magnifying device. Cork is a part of the bark of a dead oak tree.
- He noticed compartments in the cork slice. These were separated from the other by a wall or partition.
Hooke coined the term ‘cell’ for each box. These boxes appeared like a honey comb. - Cells of living organisms could be observed only after the discovery of improvised microscope.
- In 1831 Robert Brown observed Nucleus for the first time.
Question 16.
a) What invention made it possible for cells to be discovered ?
b) Why was this invention necessary for the discovery of cells ?
Answer:
a) The invention of the microscope made it possible for the cell to be discovered by Robert Hooke.
b) Robert Hooke observed thin slices of cork under a microscope. He noticed partitioned boxes or compartments in the cork slice which look like a honey comb. He also observed that one box was separated from the other by a wall or partition. Hooke coined the term “cell”.
Cells of living organisms would be observed only after the discovery of improved microscopes. Robert Hooke’s observations help to know a lot about cell structure and it’s functions because of improved microscopes having high magnifications.
Question 17.
Imagine chloroplasts are absent in plants. How does it effect living beings. Justify why chloroplasts are present only in plants but not in animals.
Answer:
- Chloroplasts contain green pigment called chlorophyll which helps in manufacture of food through the process of photosynthesis.
If chloroplasts are absent in plants food cannot be manufactured. - Since animals do not manufacture food, so they do not need chloroplasts.
- And hence, chloroplasts is found only in plant cells.
Extra Questions of Cell Structure and Functions Class 8
Question 1.
Draw sketches of some unicellular organisms you come across in this chapter.
Answer:
Question 2.
Observe the following cells. Write a note on them.
Answer:
- Red blood cells are spherical in shape. They transport food and respiratory gases in our body. .
- Muscle cells are spindle shaped and helps in the movements of our body.
Question 3.
Distinguish between Plasma membrane and Cell wall.
Answer:
Plasma membrane | Cell wall |
1) It is consisted of plasma proteins and it is a living tissue. | 1) It is made up of cellulose and it has dead tissue. |
2) It is found in both plant and animal cells. | 2) Cell wall is found in only plant cells. |
3) It is semipermeable, allows materials to pass through | 3) It is permeable doesn’t allow materials. |
4) It is soft and elastic. | 4) It is hard and rigid. |
Question 4.
What is the importance of cell wall in plant cell ?
Answer:
Cell wall performs the following functions :
- It gives definite shape to the plant cell.
- Cell wall provides rigidity and strength to the plant cell.
- It protects the inner cell organelles bounding the cell.
- Cell wall withstands the osmotic pressure which is developed by cell contents.
- It protects against variations in temperature, high wind speed, atmospheric moisture, etc.
Question 5.
Describe the structure of Nucleus.
Answer:
- The nucleus is a spherical organelle found in eukaryotic cells.
- It is responsible for controlling all activities of the cell.
- It is surrounded by a nuclear membrane.
- Nucleoplasm is present in the nucleus.
- A dark staining body nucleolus is present in the nucleus.
- Nucleus contains thread like structures called chromosomes.
- Genes are present in the chromosomes. They help in inheritance or transfer of characters from the parents to their offsprings.
Question 6.
Write the shapes and functions of the given cells.
a) Muscle cell
b) Red Blood Cells
c) Nerve cell
d) White Blood Cells
Answer:
S.No. | Name of the cell | Shape of the cell | Function of the cell |
1. | Muscle cell | Spindle shape | Running, lifting, walking etc. |
2. | Red blood cells | Round, concave on both sides | Transportation of materials like nutrients, gases like O2 and CO2 waste materials, etc. |
3. | Nerve cell | Amoeboid shape | Transmission of messages. |
4. | White blood cells | Shape of the cell | Protecting our body from disease causing organisms by providing immunity. |
Question 7.
Ask your teacher different questions to know the cells and cell organelles.
Answer:
Questionnaire :
- Why are cells considered to be basic structural units ?
- What is the outer membrane of Animal and Plant cells ?
- Name the organelles present in the cytoplasm.
- What are the functions of nucleus ?
- Where are genes located in the nucleus ? W’hat is the function of genes ?
- Differentiate cytoplasm and protoplasm.
- What are plastids ? Which plastids give green colour to the plant cells ?
- What are Prokaryotes and Eukaryotes ?
(Student can write many questions)
Question 8.
What questions will you pose to know diversity in cells ?
Answer:
- Are all cells similar in shape and size ?
- Do you find nucleus in all the cells ?
- What is the size of the smallest cell ? Give example.
- What is the size of the largest cell ? Give example.
- What is the shape of Amoeba ?
- Name the cell which is longer.
- Why are the cells different in shape and sizes ?
- Why does the nerve cell longer in size ?
Question 9.
Draw the diagrams of
a) Spherical Red Blood Cell in humans.
b) Spindle shaped muscle cells.
c) Bone cells.
d) White blood cells.
Answer:
Question 10.
a) Label the given diagram.
b) Fill in the table using the labelling.
Meaning | Name concerned |
Boundary of the cell | |
Located almost in the middle of the cell | |
Jelly like substance | |
Blank – looking structure |
Answer:
a)
b)
Function/Location of the cell organelle | Name of the cell organelle |
1) The boundary of entire cell body. | 1) Cell membrane. |
2) Almost located in the centre of the cell. | 2) Nucleus |
3) Fluid filled part of the cell. | 3) Cytoplasm. |
4) Blank – looking structure. | 4) Vacuole |
Question 11.
Observe the diagram of a cell shown below and answer the questions that follow.
A) State if the diagram is of a plant cell or an animal cell. Justify your answer.
B) State any one function for each of the following.
i) Cell membrane
ii) Nucleus
Answer:
A) The diagram is of a plant cell. Presence of cell wall justifies that the given diagram is a plant cell.
B) i) Cell membrane :
- Provides protection to the cell.
- Provides fixed environment inside a cell.
B) ii) Nucleus :
It carries genes and helps in transfer of genetic material.