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NCERT Solutions for Class 9 Science Chapter 5 – The Fundamental Unit Of Life

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NCERT Solutions for Class 9 Science Chapter 5 The Fundamental Unit Of Life: The chapter on the Fundamental Unit of Life is important for students approaching exams. This article introduces NCERT Solutions for Class 9 designed to help students explain the concepts of further learning and how to write to get good grades on exams. The solutions are presented in very simple language for ease of understanding.

NCERT Solutions for Class 9 Science Chapter 5 The Fundamental Unit Of Life explains that all living organisms are composed of cell, which is the basic structural and functional unit of life as a cell can carry out all the important functions for survival. All the cells vary in their shape, and size which is related to the functions they perform. Revise the basic concepts of The Fundamental Unit of Life for quick revision and class notes.

NCERT Solutions For Class 9 Chapter 05 of Page 51

Q1: Who discovered cells, and how?

Answer:

Cells were discovered by a British biologist, Robert Hooke, in 1665. He observed cells in a cork slice (dead cell walls of plant cells) under his self-developed microscope and noticed some honeycomb-like small compartments. He called them as cells.

Q2: Why is the cell called the structural and functional unit of life?

Answer:

Cells are the basic structural and functional unit of life because they are the ultimate living smallest units. They aggregate to form tissues, which perform similar functions. A cell has the potential to perform all the physiological activities and life processes like nutrition, excretion, respiration, transportation, etc. This is why a cell is called the structural and functional unit of life.

NCERT Solutions For Class 9 Chapter 05 of Page 53

Q1:  How do substances like CO2 and water move in and out of the cell? Discuss.

Answer:

Carbon dioxide is a gaseous molecule that moves in and out of the cell by diffusion. Diffusion is a process in which the molecules are transported from a region of higher concentration to a region of lower concentration. Water moves in and out of the cell through osmosis. Osmosis is a process in which molecules are transported from a region of higher concentration to a region of lower concentration through a semi-permeable membrane.

Q2: Why is the plasma membrane called a selectively permeable membrane?

Answer:

The plasma membrane is called the selectively permeable membrane because it regulates the movement of substances in and out of the cell. This means that the plasma membrane allows certain materials to pass while preventing other materials from passing through.

NCERT Solutions For Class 9 Chapter 05 of Page 55

Q1: Fill in the gaps in the following table, illustrating the differences between prokaryotic and eukaryotic cells.

Prokaryotic cellEukaryotic cell
1. Size: Generally small (1-10 μm)
1 μm = 10-6m
 1. Size: Generally large (5-100 μm)

2.   Nuclear region:

______________________________

______________________________

and known as ___________________

2. Nuclear region: well-defined and surrounded by a nuclear membrane.
3.  Chromosome: single3. More than one chromosome.
4.  Membrane-bound cell organelles absent.

4. ______________________________

______________________________

______________________________.

Answer:

Prokaryotic cellEukaryotic cell
1. Size: Generally small (1-10 μm)
1 μm = 10-6m
1. Size: Generally large (5-100 μm)
2.   Nuclear region: is poorly defined and nuclear content is scattered in the centre and known as nucleoid.2. Nuclear region: well-defined and surrounded by a nuclear membrane.
3.  Chromosome: single3. More than one chromosome.
4.  Membrane-bound cell organelles absent.4. Membrane-bound cell organelles present.

NCERT Solutions For Class 9 Chapter 05 of Page 57

Q1: Can you name the two organelles we have studied that contain their own genetic material?

Answer:

Mitochondria and plastids are the cell organelles with their own genetic material.

Q2: If the organization of a cell is destroyed due to some physical or chemical influence, what will happen?

Answer:

If the organization of the cell is destroyed by physical or chemical influences, the cell cannot perform basic functions such as respiration, nutrition, excretion, transport, etc.

Q3: Why are lysosomes known as suicide bags?

Answer:

Lysosomes are known as the cell’s suicide bags because when a cell is damaged, one of the lysosomes breaks down and releases digestive or hydrolytic enzymes that digest its own cell, ultimately causing cell death.

Q4: Where are proteins synthesized inside the cell?

Answer:

Protein synthesis takes place in the ribosomes of the cell. Hence they are known as the protein factories or machinery of the cell.

NCERT Solutions For Class 9 Chapter 05

Q1: Make a comparison and write down ways in which plant cells are different from animal cells.

Answer:

The differences between plant and animal cells are given below:

Plant cellAnimal cell
The cell wall is present and made up of cellulose.It doesn’t have a cell wall.
Plastids are present, and responsible for photosynthesis.Plastids are absent.
Mitochondria are present but very few in number.Numerous mitochondria are present.
Vacuoles are large, prompt, and centrally located.Vacuoles are small in size or absent.
Its shape is square or rectangular.Its shape is irregular or round.

Q2: How is a prokaryotic cell different from a eukaryotic cell?

Answer:

Prokaryotic cellEukaryotic cell
A true nucleus is absent, nuclear content is scattered in the center which is known as the nucleoid. The nuclear membrane is not present around the nucleoidThe true nucleus is present i.e. surrounded by a nuclear membrane
More than one chromosome is presentOne chromosome is present which is not true (plasmid)
Membrane-bound cell organelles are absentMembrane-bound cell organelles are present e.g. mitochondria, ER. Ribosomes are common in both prokaryotic and eukaryotic cells
Genetic recombination is partial, unidirectionally transfer DNAMeiosis and fusion of gametes occur
Examples- Bacteria, archaeaExamples- Plants and animals

Q3: What would happen if the plasma membrane ruptures or breaks down?

Answer:

If the plasma membrane is ruptured, the cell will not allow the exchange of materials from the outside by osmosis or diffusion, since the plasma membrane is semi-permeable in nature.  Injury or breakdown of the plasma membrane makes it depolarized which results in the loss of membrane potential. This leads to the inhibition of protein synthesis, DNA, and RNA synthesis and hence, the death of a cell.

Q4: What would happen to the life of a cell if there was no Golgi apparatus?

Answer:

Without the Golgi apparatus, lysosomes would not be produced, resulting in a buildup of dead and damaged organelles. The Golgi apparatus is responsible for the transport, modification, and packaging of fats and proteins into small vesicles, which are then delivered to their destination. This can lead to cell disorders and cell death.

Q5: Which organelle is known as the powerhouse of the cell? Why?

Answer:

Mitochondria are known as the powerhouses of the cell. Inside the cells are mitochondria, which are involved in the release of energy from food or glucose molecules in the respiratory process. The energy released is in the form of ATP (adenosine triphosphate). ATP is known as the energy currency of the cell.

Q6: Where do the lipids and proteins constituting the cell membrane get synthesized?

Answer:

The lipids and proteins constituting the cell membrane are synthesized in the ER, i.e. endoplasmic reticulum.

Q7: How does an Amoeba obtain its food?

Answer:

Pseudopodia are the temporary finger-like projections in the amoeba that aid in capturing food, changing its size and shape. The food could be a bacterium or algae. An Amoeba obtains its food by holozoic mode of nutrition which involves ingestion, digestion, absorption, assimilation, and egestion. The process of intake of food is called phagocytosis. The diagrammatic representation is given below:

Phagocytosis

Q8: What is osmosis?

Answer:

Osmosis is the movement of molecules from a region of higher concentration to a region of lower concentration through a semi-permeable membrane.

Q9: Carry out the following osmosis experiment:

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 of sugar in cup B
  • Put one teaspoon salt in cup C
  • Put one teaspoon of sugar in the boiled potato cup D.

Keep these for two hours. Then observe the four potato cups and answer the following:

  1. Explain why water gathers in the hollowed portion of B and C.
  2. Why is potato A necessary for this experiment?
  3. Explain why water does not gather in the hollowed-out portions of A and D.

Answer:

  • Water collects in cups B and C because the two have different concentrations of water in the trough and water in the potato cup. Therefore, osmosis occurs because the potato cells act as a semi-permeable membrane.
  • Potato A is essential for the comparative test in this experiment and serves as a control or standard.
  • Water does not collect in the hollow parts A and D. Because cup A does not change its concentration, allowing the water to drain. For osmosis to occur, one of the concentrations must be greater than the other.
    • In glass D, the cells are dead, so there is no semi-permeable membrane to allow the passage of water, and there is no osmosis.

Q10: Which type of cell division is required for the growth and repair of the body, and which type is involved in the formation of gametes?

Answer:

There are two types of cell division:

  1. Mitosis
  2. Meiosis

Meiosis is involved in the formation of gametes which reduces the number of chromosomes in gametes, e.g. eggs or sperm. 

Also Check:

FAQ’s on NCERT Solutions for Class 9 Science Chapter 5

Q1. How are the NCERT Solutions for Class 9 Science Chapter 5 structured on GeeksforGeeks?

The NCERT Solutions crafted by GeeksforGeeks adhere meticulously to the latest CBSE guidelines, offering precise and reliable reference material for students preparing for their CBSE exams. These solutions foster a deep understanding of key concepts, crucial for success in exams. Each topic is supplemented with illustrative examples and visual aids, enhancing students’ comprehension through visual learning. By promoting smart learning and honing efficient answering skills, these solutions contribute to improved academic performance and higher scores.

Q2. What are the topics and subtopics included in Chapter 5 of NCERT Solutions for Class 9 Science?

This are the topics and subtopics covered in Chapter 5 of NCERT Solutions for Class 9 Science:

1. Nucleus

2. Cell Organelles

3. Plasma Membrane or Cell Membrane

4. What Are Living Organisms Made Up of?

5. What Is a Cell Made Up of? What Is the Structural Organisation of a Cell?

6. Cell Wall

7. Cytoplasm

Q3. How can students benefit from the CBSE Free PDF Download available through online free resources for their studies?

Students can benefit significantly from the CBSE Free PDF Download available through online free resources by accessing study materials, textbooks, and other educational resources at no cost. These PDFs can serve as valuable supplements to their learning, enabling them to review, practice, and deepen their understanding of various subjects and topics. It offers a convenient and accessible way to study and prepare for exams without the need for physical textbooks, making it a cost-effective and flexible option for students seeking quality educational materials.



Last Updated : 11 Sep, 2023
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