In this section, you will get “The Fundamental Unit Of Life class 9 notes pdf which is chapter 5 of class 09 science”. These notes have been prepared by the subject experts who have a teaching experience of more than 10 years. These notes will be very useful for you.
The Fundamental Unit Of Life questions and answers
In this section, you will get The fundamental unit of life class 9 chapter 5 questions and answers. These questions and answers will ease your exam preparation and will help you excel.
Who discovered cell and how?
Robert Hooke in 1665 discovered the cell.
He examined thin slices of cork under a self-designed primitive microscope. The cork is substance obtained from the bark of a Spanish Oak tree-Quercus.
These thin slices of cork resembled the structure of honey comb. The latter consisted of many tiny compartments. He called them cellulae (singular-cella), now termed cells. Cellula is a Latin name which means “a little room”.
Why is the cell called the structural and functional unit of life?
All living organisms are made up of cells. Thus, cell is the structural unit of life. Each cell requires distinct structure and function due to the organization of its membrane and cytoplasm organelles in specific way. Such an organization enables the cells to perform basic functions such as respiration, obtaining nutrition, clearing of waste material, forming the proteins etc. the cell is therefore, the basic functional unit of living organisms.
How do substances like Co2 and water move in and out of the cell?
Co2 moves in and out of the cells by the process of diffusion which involves movement of molecules from higher concentration to lower concentration across the cell membrane.
Water moves in and out of the cells by osmosis. Osmosis is the movement of water or solvent through a semipermeable membrane from a solution of lower concentration of solutes to a solution of higher concentration of solutes to which the membrane is relatively impermeable.
Why is the plasma membrane called a selectively permeable membrane?
The plasma membrane permits the entry and exit of some materials in and out of the cell, and it also prevents movement of some other materials. It is owing to this reason that the plasma membrane, is called a selectively permeable membrane.
Can you name the two organelles we have studied that contain their own genetic material?
Chloroplasts and Mitochondria
If the organisation of a cell is destroyed due to some physical or chemical influence, what will happen?
A well-organized cell maintains homeostasis, i.e. constant internal chemical composition. It is, therefore, able to perform basic functions like respiration, obtaining nutrition, cleaning of wastes, forming new proteins etc.
If the organization of a cell is destroyed, it will not be able to maintain homeostasis and thus will not be able to perform basic functions.
Why are lysosomes known as suicide bags?
Lysosomes are called the Suicidal bags of the cell as they contain hydrolytic enzymes which can digest incoming food materials, remove the foreign bodies, toxic molecules and debris, breakdown worn out cells & cell organelles to component molecules for building new organelles and cells.
Where are proteins synthesized inside the cell?
Proteins are synthesised in the ribosomes inside the cell.
Make a comparison and write down ways in which plant cells are different from animal cells.
Plant cells differ from animal cells in the following ways;
| Animal Cell | Plant Cell |
| Generally smaller in size (less than 100 micro meter) | Generally large in size (100 micro meter long) |
| It is enclosed by a thin, flexible, living plasma membrane only. | It is enclosed by a thick, rigid, deed cell wall in addition to plasma membrane. |
| It has many temporary vacuoles. | It has a large permanent central sap vacuole. |
| Centrosomes are present practically in all animal cells. | Centrosomes occur only in motile cells of lower plants. |
| Plastids are absent. | Plastids are usually present. |
| Contractile vacuoles may occur to pump out excess water. | There is no contractile vacuole. |
| Animal cell may change form and move about. | Cell wall prevents change in form and position of the plant cells. |
| Stores carbohydrates as glycogen. | Stores carbohydrates as starch. |
How is a prokaryotic cell different from a eukaryotic cell?
Prokaryotic cell is different from a eukaryotic cell in the following ways:
| Prokaryotic cell | Eukaryotic cell |
| Generally small in size (1-10 micro meter) | Generally large in size (5-100 micrometer) |
| Cell wall, if present is made up of peptidoglycan (murine). Example Bacteria | Plant cell walls are made up of cellulose. |
| The nucleoid (genetic material) is not surrounded by a nuclear membrane and is in direct contact with cytoplasm absent. | True nucleus is present. It consists of nuclear envelope, nucleoplasm, chromosomes and nucleolus |
| Membrane bound cell organelles are absent. | Membrane bound cell organelles like, mitochondria, plastids, E.R, Golgi bodies etc. are present. |
| Ribosomes are small 70s type. | Ribosomes are large 80s type. |
| Many prokaryotic cells possess Pilli and Plasmids. | Plasmids and Pilli are absent. |
| For example: Bacteria, Cyanobacteria, Mycoplasma | For example: Fungi, plants and animals. |
What would happen if the plasma membrane ruptures or breaks down?
Plasma membrane is a selectively permeable membrane that helps the cell maintain its homeostasis, i.e. constant internal chemical composition of the cell. If it ruptures or breakdown, the constant internal chemical composition of the cell will be lost and it will not be able to perform functions.
What would happen to the life of a cell if there was no Golgi apparatus?
Golgi apparatus is involved in the storage, modification and packaging of materials in vesicles. It is also involved in the formation of lysosomes. The basic metabolic functions of the cells are not possible if Golgi apparatus is not there.
Which organelle is known as the powerhouse of the cell? Why?
Mitochondrion is known as the power of the cell. It is because they contain enzymes that are needed for stepwise oxidation of food stuffs present in the cells to Co2and water. Oxidation of food releases energy which is used to form high energy ATP molecules. ATP is used to bring about energy requiring activities of the cell.
Where do the lipids and proteins constituting the cell membrane get synthesized?
Smooth endoplasmic reticulum (SER) helps in the manufacturing of lipids which are important for cell function. Ribosomes are the sites of protein synthesis.
How does an Amoeba obtain its food?
Amoeba acquires its food through Endocytosis. Endocytosis refers to invagination of a small region of the plasma membrane, and ultimately forming an intra-cellular membrane bound vesicle. This process is generally involved for the ingestion of food material. Intake of liquid food using Endocytosis is called pinocytosis or cell drinking. Similarly, intake of solid food particles by a cell through its cell membrane is called Phagocytosis or cell eating.
What is osmosis?
It is the diffusion of water or solvent through a semi-permeable membrane from a solution of lower concentration of solutes to a solution of higher concentration of solutes, to which the membrane is relatively impermeable, is called osmosis.
Which type of cell division is required for growth and repair of body and which type is involved in formation of gametes?
The cell division required for growth and repair of body is mitosis and the cell division involved in the formation of gametes is meiosis.
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