Cell Structure and Functions Class 8 Important Questions and Answers
Important questions of Class 8 Science Chapter 8 Cell Structure and Functions is given below. These important questions will help students while preparing for the exam. Practising these important questions will analyse their performance and work on their weak points. Score well in exam of Class 8 Science by going through these important questions. Students of Class 8 can download important questions of Class 8 Science Chapter 8 Cell Structure and Functions PDF by clicking the link provided below.
Important Questions of Class 8 Science Chapter 8 Cell Structure and Functions
Here you can get Class 8 Important Questions Science based on NCERT Text book for Class 8. Science Class 8 Important Questions are very helpful to score high marks in board exams. Here we have covered Important Questions on Cell Structure and Functions for Class 8 Science subject.
Very Short Answer Questions
1. How many types of things are there on earth?
Answer: There are two types of things:
(i) Living things
(ii) Non-living things.
2. Name the structural unit of an organism.
Answer: Cell.
3. What is cell?
Answer: The structural and functional unit of life is called cell.
4. What is cork?
Answer: Cork is the part of bark of a tree.
5. Who discovered the cell and when?
Answer: Robert Hooke discovered the cell in 1665.
6. What is basic structural unit of a building?
Answer: Bricks.
7. Is hen’s egg a cell or group of cells?
Answer: Hen’s egg is a cell.
8. Name a cell which can be seen by an unaided eye.
Answer: Hen’s egg.
9. How do scientists observe and study the living cells?
Answer: By using highly magnifying microscopes.
10. How many cells are there in human body?
Answer: There are trillions of cells in human body.
11. How many types of organisms are there on the basis of number of cells?
Answer: There are two types of organisms on the basis of number of cells:
(i) Unicellular
(ii) Multicellular.
12. Name two unicellular organisms.
Answer: Amoeba, Paramecium.
13. Name two multicellular organisms.
Answer: Man, Dog.
14. What are tissues?
Answer: The groups of specialised cells to perform a special function are called tissues.
15. How can you define the shape of amoeba?
Answer: The shape of amoeba is irregular.
16. What are pseudopodia?
Answer: The finger like projections of different lengths out of the body of amoeba are called pseudopodia.
17. Name two cells which can change their shape.
Answer: (i) Amoeba cell
(ii) WBC
18. Mention three different shapes of cells in human body.
Answer: (i) Spherical red blood cells
(ii) Spindle shaped muscle cells
(iii) Long branched nerve cell.
19. Which part of the cell gives the shape to a cell.
Answer: Cell wall or Plasma membrane.
20. What are the basic components of a cell?
Answer: (i) Cell membrane
(ii) Cytoplasm
(iii) Nucleus.
21. What are chromosomes?
Answer: The thread-like structures in the nucleus are called chromosomes.
22. Write the name of unit of inheritance in living things.
Answer: Gene.
23. Name the part of a cell which helps in control of the activities.
Answer: Nucleus.
24. What is protoplasm?
Answer: The living substance of the cell is called protoplasm.
25. What is nuclear membrane?
Answer: The membrane used to cover the nucleus and separate it from cytoplasm is called nuclear membrane.
26. How many types of cells are there?
Answer: There are two types of cells:
(i) Prokaryotic cells
(ii) Eukaryotic cells.
27. What are prokaryotic cells?
Answer: The cells having nuclear material without nuclear membrane are called prokaryotic cells.
28. Name the organisms having prokaryotic cell.
Answer: Bacteria and blue green algae.
29. What are eukaryotic cells?
Answer: The cells having well organised nucleus with a nuclear membrane are called eukaryotic cells.
30. Name the organisms having eukaryotic cells.
Answer: All organisms, other than bacteria and blue green algae, have eukaryotic cells.
31. What are prokaryotes and eukaryotes?
Answer: The organisms having prokaryotic cells are called prokaryotes and those having eukaryotic cells are called eukaryotes.
32. What are vacuoles?
Answer: The blank looking structures in the cytoplasm are called vacuoles.
33. What are plastids?
Answer: The small coloured bodies in plant cells are called plastids.
34. Name the green coloured plastids.
Answer: Chloroplasts.
35. Write the name of pigment found in chloroplasts.
Answer: Chlorophyll.
Short Answer Type Questions
1: If there is any difference between the vacuoles sizes in plant and animal. Explain.
Answer: The vacuoles size varies in plant and animal. Plant cell have single large sized vacuole, whereas animal cell have numerous small sized vacuoles.
2: Differentiate between unicellular and multicellular organisms.
Answer: Organisms made up of single cell are called unicellular organisms. Organisms made up of more than one cell are called multicellular organisms.
3: Explain how Pseudopodia are helpful for Amoeba.
Answer: Pseudopodia help Amoeba in movement and in capturing the food.
4: Name the part of cell which provides its shape.
Answer: Cell membrane provides cell its shape. Cell membrane is important for movement of substance both inward and outward of cell.
5: Which component provides rigidity to plant cell?
Answer: Cell wall provides rigidity to plant cell.
6: Define Tissue.
Answer: Tissue is a group of similar cells performing a specific function.
7: Differentiate between Prokaryotes and Eukaryotes.
Answer: Prokaryotes do not have well organised nucleus and Eukaryotes have well organised nucleus with nuclear membrane.
8: Relate Tissue to cell and organ.
Answer: Tissue is composed of cell and Organ is made up of tissue.
9: Give example of some unicellular and multicellular organisms
Answer: Unicellular organisms: Amoeba and Paramecium.
Multicellular organism: Human and Mouse.
10: Define the function of Plasma membrane.
Answer: Functions of Plasma membrane:
- Shape to the cells of plants and animals.
- Separates cells from one another and also the cell from the surrounding medium.
- Allows the movement of substances or materials both inward and outward.
11: Define the functions of Cell wall.
Answer: Functions of Cell wall:
- Gives rigidity to plant cell.
- Protection against variations in temperature, high wind speed, atmospheric moisture, etc.
12: Define the function of Nuclear membrane.
Answer: Function of Nuclear membrane:
- Separates nucleus from cytoplasm.
- Allows the movement of materials between the cytoplasm and the inside of the nucleus
13: Define Protoplast and name its components.
Answer: The entire content of a living cell is known as protoplasm.It includes the cytoplasm and the nucleus.
14: Define Plastids.
Answer: Plastids are coloured bodies found in the cytoplasm of plant. They are of different colour.
15: What is Chloroplast?
Answer: Chloroplast is green coloured plastid. It provides green colour to leaf.
16: Define the functions of Chloroplast.
Answer: Chloroplast is essential for photosynthesis and it provide green colour to leaf of plant.
17: What is Chromosome?
Answer: Chromosomes are thread like structure within nucleus.
18: Define the function of Nerve Cell.
Answer: Nerve Cell nerve cell receives and transfers messages, thereby helping to control and coordinate the working of different parts of the body.
19: Give two examples of both Prokaryotes and Eukaryotes.
Answer: Prokaryotes: Bacteria and Blue-green algae
Eukaryotes: Human and Plant
20: Define Gene and its function.
Answer: Gene is a unit of inheritance in living organisms.
Function: Controls the transfer of character from parents to offspring.
21. Explain the discovery of cell.
Answer: In 1665, Robert Hooke observed slices of cork under a magnifying device. He noticed partitioned boxes or compartments in the cork slice. These boxes appeared like honeycomb. Hooke coined the term cell for each box.
22. Cells are the building blocks of the life. Explain.
Answer: Cells are the basic structural unit of life like bricks which are basic structural unit of buildings. Buildings are not same at all. In the same way organisms also differ from each other. Both cells and bricks are basic units of structure. So we can say that cells are building blocks of life.
23. Explain various types of organisms on the basis of number of cells.
Answer: There are two types of organisms on the basis of number of cells:
(i) Unicellular: The organisms that contain only single cell in their body are called unicellular organisms. For example: amoeba and paramecium.
(ii) Multicellular: The organisms made up of more than one cell are called multicellular organisms. For example: human, cat, dog etc.
24. What are the functions performed by single cell organisms?
Answer: Single celled organisms capture and digest food, respire, excrete, grow and reproduce like multicellular organisms. The multicellular organisms do these functions by groups of specialised cells forming different tissues.
25. Define the shape of amoeba.
Answer: The shape of amoeba appears irregular. Amoeba has no definite shape unlike other organisms. It keeps on changing its shape. It contains finger-like projections called pseudopodia (false feet). These projections appear and disappear as amoeba moves or feeds.
26. Why could cells not be observed before 17th century?
Answer: The size of cells is mostly very small. We cannot see them by unaided eyes. They can be seen by high power microscope. Before 17th century the microscope was not discovered. That is why the cells could not be observed before 17th century.
27. Explain the variation of size of cells.
Answer: Cells vary in their size. Some cells are very small like bacterial cell whose size is about 0.5 micrometre. Nerve cell is the longest in our body. Ostrich egg is the largest cell. Acetabulum is the largest unicellular algae which is about 10 cm long. In this way size of the cells varies.
28. Explain the structure of a cell.
Answer: There are three main components of a cell:
(i) Cell membrane
(ii) Cytoplasm
(iii) Nucleus
The cytoplasm and nucleus are enclosed within the cell membrane. The cell membrane is also called plasma membrane. The membrane separates cells from one another. The plasma membrane is porous and allows the movement of substances or material both inward and outward.
29. Explain the structure of onion cell with the help of a slide.
Answer: Observe the slide under a microscope having small piece of onion peel:
(i) Cell membrane: The boundary of the onion cell is cell membrane. It is covered by another thick covering called the cell wall.
(ii) Nucleus: The central dense round body in the centre is called the nucleus.
(iii) Cytoplasm: The jelly-like substance between nucleus and cell membrane is called cytoplasm.
30. Write the functions of cell wall.
Answer: In addition to the cell membrane, there is an outer thick layer in cells of plants called cell wall. It gives the shape to the cell. Cell wall provides protection to the cells of the plants. Plant cells need protection against variations in the temperature, high wind speed and atmospheric moisture etc.
31. Explain the structure of cheek cells.
Answer: Take a matchstick with the tip broken. Scrape inside your cheek without hurting it. Place it in a drop of water on a glass slide. Add a drop of iodine and cover it with cover slip. Observe it under a microscope. We observe that cheek cells also contain cell membrane, cytoplasm and nucleus. There is no cell wall in the animal cells.
32. What is cytoplasm?
Answer: Cytoplasm is the jelly-like substance present between cell membrane and the nucleus. Various other components called organelles are present in the cytoplasm. These are mitochondria, Golgi bodies, ribosomes etc.
33. Write the functions of mitochondria, Golgi bodies and ribosomes.
Answer: Mitochondria: It performs the function of respiration and provides the cell with energy. It is called power house of a cell.
Golgi bodies: They synthesise, store and secrete enzymes and proteins.
Ribosomes: They help in the synthesis of proteins.
34. Explain prokaryotic and eukaryotic cells.
Answer: Prokaryotic Cells: The cells having nuclear material without nuclear membrane are termed as prokaryotic cells and organisms with these kinds of cells are called prokaryotes. Examples: bacteria and blue green algae.
Eukaryotic Cells: The cells having well organised nucleus with a nuclear membrane are called eukaryotic cells. The organisms with these kinds of cells are called eukaryotes. For example, all organisms other than bacteria and blue green algae are eukaryotes.
Long Answer Type Questions
1: What is Cell? Define its components.
Answer: Cell is the structural unit of living organisms.
Components:
- Cytoplasm is a jelly-like substance present between the cell membrane and nucleus.
- Nucleus is spherical shaped component located in the centre of the cell. It acts as control centre of activities of cell.
- Plasma membrane is a porous membrane surrounding the cytoplasm.
2: Define “Why plants need cell wall?”
Answer: Cell wall provides rigidity to plant cell. This provides plant cell protection against the variation of environmental condition like variation in temperature, humidity etc.
3: “Single cell organisms perform all the function that multicellular organisms perform.” Define what functions are these. Also define who perform all these function in multicellular.
Answer: Single-celled organism performs all function that multicellular organisms perform. These functions are capturing and digestion of food, respiration, excretion, growth and reproduction.
In single-celled organism these functions are performed by overall cell. However, in multicellular organism each function is performed by specific organ.
4. Explain the position and functions of nucleus in a cell.
Answer: Nucleus is the most important component of the living cell. It is round or spherical in shape and situated in the centre of the cell. Nucleus is separated from cytoplasm by a membrane called nuclear membrane. This membrane is porous and allows the movement of materials between the cytoplasm and inside of the nucleus. There is a small and spherical body in the nucleus. It is called nucleolus. Nucleus contains thread-like structures called chromosomes. These carry genes and help in inheritance or transfer of characters from the parents to the offspring. Nucleus also acts as a control centre of the activities of the cell.