NCERT Solutions for The Fundamental Unit of Life Class 9 Chapter 5 Science has all the solutions to the questions provided in the NCERT Book of the latest edition.
Students are advised to practice all the questions to get good marks in the board examination.
| Textbook | NCERT |
| Class | 9 |
| Subject | Science |
| Chapter | 5 |
| Chapter Name | The Fundamental Unit of Life |
| Category | NCERT Solution |
Class 9 Science Chapter 5 The Fundamental Unit of Life NCERT Solution
The Fundamental Unit of Life Intext Questions Page 51
Who discovered cells, and how?
Answer
Cells were first discovered by Robert Hooke in 1665. He observed the cells in a cork slice with the help of a primitive microscope.
Why is the cell called the structural and functional unit of life?
Answer
Cells form tissues, which form organs, which work in coordination to act as an organ system. The cells are the basic unit of life which is capable of doing all the work on its own.
This helps to maintain the structure and functioning of the multicellular organisms. Also, the single cell has all the necessary organelles which will help it to survive independently. So they are called the structural and functional unit of life.
The Fundamental Unit of Life Intext Questions Page 53
How do substances like CO₂ and water move in and out of the cell? Discuss.
Answer
Diffusion is the process by which CO₂ moves out of the cell. It has comparatively high concentration inside the cell than the surroundings.
H₂O moves by osmosis through the plasma membrane from higher concentration to the region with lower concentration.
Why is the plasma membrane called a selectively permeable membrane?
Answer
Because it allows movement of specific substances. Not all substances can move freely through plasma membranes.
The Fundamental Unit of Life Intext Questions Page 55
Fill in the gaps in the following table illustrating differences between prokaryotic and eukaryotic cells
Answer
| | Prokaryotic cell | | Eukaryotic cell |
|---|---|---|---|
| 1. | Size: generally small (1-10 µm) 1 µm = 10-6 m | 1. | Size: generally large (5-100 µm) |
| 2. | Nuclear region: is poorly defined and devoid of nuclear membrane, and is known as nucleoid | 2. | Nuclear region: well-defined and surrounded by a nuclear membrane |
| 3. | Chromosome: single | 3. | More than one chromosome |
| 4. | Membrane-bound cell organelles absent | 4. | Membrane-bound cell organelles such as mitochondria, plastids, etc., are present |
The Fundamental Unit of Life Intext Questions Page 57
Can you name the two organelles we have studied that contain their own genetic material?
Answer
Mitochondria and plastids
If the organisation of a cell is destroyed due to some physical or chemical influence, what will happen?
Answer
In such cases lysosomes will burst and release their enzymes which will ultimately digest the cell itself
Why are lysosomes known as suicide bags?
Answer
Because they have enzymes that can digest the cell.
Where are proteins synthesised inside the cell?
Answer
They are synthesised in ribosomes. They are found in relation with rough endoplasmic reticulum
The Fundamental Unit of Life Exercise Questions
Make a comparison and write down ways in which plant cells are different from animal cells
Answer
| Characteristics | Plant cell | Animal cell |
|---|---|---|
| Cell wall | Present | Absent |
| Vacuole | Present | Absent |
| Shape | With distinct edges, square or rectangular | Round and irregular shaped |
| Lysosomes | Rarely present | Present |
| Chloroplast | Present | Absent |
| Nucleus position | At side of the cell | At center of the cell |
How is a prokaryotic cell different from a eukaryotic cell?
Answer
| Prokaryotic cell | Eukaryotic cell | |
|---|---|---|
| Size | 1-10 micro m. | 5-10 micro m. |
| Nuclear region | Not well defined | Well defined |
| Membrane bound organelles | Absent | Present |
What would happen if the plasma membrane ruptures or breaks down?
Answer
If the plasma membrane breaks down, the selective permeability of the cell will be lost which cause the exposure of cell component to the external environment and would ultimately result in cell death.
What would happen to the life of a cell if there was no Golgi apparatus?
Answer
If there is no Golgi apparatus then the lysosomes would not be produced, and the accumulation of dead damaged organelles and the molecules in the cell would ultimately result in cell death.
Also none of the structural or functional proteins will reach their destination. Resulting in the dysfunction of the target cell or organ or organelle.
Which organelle is known as the powerhouse of the cell? Why?
Answer
Mitochondria is the powerhouse of the cell. As it releases the energy in the form of ATP needed by the cell to perform various functions.
Where do the lipids and proteins constituting the cell membrane get synthesised?
Answer
They are synthesised in Endoplasmic Reticulum
How does an Amoeba obtain its food?
Answer
Amoeba obtains its food by phagocytosis. It is a process by which the food is engulfed by the amoeba. When the food comes in contact with the external membrane the food particle gets incorporated in the form of a vesicle and is then digested
What is osmosis?
Answer
It is the process of movement of water molecules from higher concentration to lower concentration through a semipermeable membrane.
Carry out the following osmosis experiment:
Answer
Take four peeled potato halves and scoop each one out to make potato cups. One of these potato cups should be made from a boiled potato. Put each potato cup in a trough containing water. Now,
- Keep cup A empty
- Put one teaspoon sugar in cup B
- Put one teaspoon salt in cup C
- Put one teaspoon sugar in the boiled potato cup D. Keep these for two hours. Then observe the four potato cups and answer the following:
Answer
- Due to the presence of water level differences. Endo-osmosis occurs.
- We need potato A to compare the changes occurring in the other potatoes. As it shows that only a potato cavity cannot bring any movement of water without any change in concentration.
- Water does not gather in the hollowed portion of potato A as it was empty. Water also not gather in the cup D because the potato used was boiled which makes it inactive as after boiling its protein structure were denatured, resulting in the disruption of the cell membrane.
Which type of cell division is required for growth and repair of body and which type is involved in formation of gametes?
Answer
For growth we need mitosis and for gametes formation, meiosis is required
Hope NCERT Solutions for Class 9 Science Chapter 5 The Fundamental Unit of Life, helps you in solving problems. If you have any doubts, drop a comment below and we will get back to you.