NCERT Solutions for the structural and Fundamental Unit of Life-Cell Class 9th
NCERT Solutions for the structural and Fundamental Unit of Life-Cell Class 9th
Here you get all the NCERT solutions for the chapter structural and fundamental unit of life cell. In this you will get all the answers with all the questions. You will also be provided with the NCERT Exercise, HOT’s questions i.e high level value-based question as well as sample papers and other study material.
NCERT Text Book Chapter 5 Question
Question1. Who discovered cells and how?
Ans.1) Robert Hook discovered the cell in 1665. He examined a thin slice of cork under a self-designed crude microscope and observed that the cork resembled the structure of a honey comb. The latter consisted of many tiny compartments. Hook called them Cellular (Singular cellula), now termed as Cell. Cellula is a Latin name that means ‘a little room’. Such rooms were also present in monasteries.
Question 2. Why is cell called the structural and functional unit of life?
Ans.2) All living organisms are made up of cells. Thus, cell is the structural unit of life. Each living cell has the capacity to perform certain basic function that are characteristics of all living forms. Each cell acquired distinct structure and function due to the organization of its membrane and cytoplasmic organelles in a specific way. Each kind of cell organelle performs a special function, such as making new materials in the cell, clearing up the waste material from the cell, utilization of oxygen in oxidation of food and energy production, movement, etc. A cell is able to live and perform all its functions because of these organelles. These organelles together constitute the basic unit of structure and function called the cell.
Question 3. How do the substance like carbon-di-oxide and water move in and out of the cell?
Ans.3) Co2 moves in and out of the cell by the process of diffusion. Diffusion involves movement of molecules of from higher concentration to lower concentration across the plasma membrane. Water moves in and out of the cell by Osmosis. Osmosis is the movement water or solvent through a semi-permeable membrane from a solution of lower concentration of solutes to a solution of higher concentration of solutes through which the membrane is relatively impermeable.
Both diffusion and osmosis are physical or mechanical processes and do not require spending of energy for their performance by the cell.
Question 4. Why is plasma membrane called a selective permeable membrane?
Ans.4) Plasma membrane is called the selective permeable membrane as it only allows selective material to pass through it. It only allows the movement of molecules across it and not all of them.
Question 5. Fill in the gaps in the following table illustrating difference between prokaryotic cell and eukaryotic cells.
1. Size: Generally small(1-10 µm )
1. Size: Generally large (5-100 Mm)
2. Nuclear region:____________
and known as _____________
2. Nuclear region: Well defined and surrounded by a nuclear membrane.
3. Chromosome: single
3. Chromosome: more than one.
4. Membrane-bound organelles: absent
Ans. 5) It lies in the cytoplasm and not cover with a nuclear membrane, nucleotide.
4. membrane-bound cell organelles such as mitochondria, plastids, Golgi apparatus, Lysosomes, etc., are present in the cytoplasm.
Question6. Can you name the two organelles we have studied that contain their own genetic material?
Ans. 6) (a) Mitochondria;
Question7. If the organisation of cell is destroyed due to some physical and chemical influence, what will happen?
Ans. 7) A well maintained and organized cell maintains homeostasis, i.e., constant internal chemical composition. It is, therefore, able to perform basic function such as respiration, obtaining nutrition, clearing of waste, forming new proteins, etc. If the organization of a cell is destroyed, it will not be able maintain homeostasis and thus will not be able to perform above said basic functions and such a cell will ultimately die.
Question8. Why are lysosomes are known as suicide bags?
Ans. 8) Lysosomes contain digestive enzymes for almost all types of organic materials. If their covering membrane breaks as it happens during injury to cell, digestive enzymes will spill over the cell contents and digest the same. As lysosomes are organelles which on bursting can kill cell possessing them, they are called suicide bags.
Question9. Where are proteins synthesized inside the cell?
Ans. 9) Proteins are synthesized in the ribosomes.
Question1. Make a comparison table and write down ways in which plant cell are different from animal cell.
|1. Animal cells are usually small in size.
2. Cell wall is absent.
3. Except the protozoan Euglena, no animal cell possesses plastids.
4. Vacuoles in animal cells are many, small and temporary.
5. Animal cell have a single highly complex and prominent Golgi apparatus.
6. Animal cells have centrosomes and centrioles.
|1. Plant cells are larger than animal cells.
2. The plasma membrane of plant cell is surrounded by a cell wall of cellulose.
3. Plastids are present.
4. Most mature plants have a permanent and large central sap vacuole.
5. Plant cells have many simpler units of Golgi apparatus, called dictyosomes.
6. Plant cells lack centrosomes and centrioles.
Question2. How is a prokaryotic cell is different from a eukaryotic cell?
|1. Size of a cell is generally small (1-10µm).
2. Nucleus is absent (Nuclear region or nucleoid is surrounded not surrounded by a membrane)
3. It contains single chromosome.
4. Nucleolus is absent.
5. Membrane-bound cell organelles are absent.
6. Cell division takes place by fission or building (no mitosis).
|1. Size of cell is generally large (5-10 mm).
2. Nucleus is present (Nuclear material is surrounded by a nuclear membrane).
3. It contains more than one chromosome.
4. Nucleolus is present.
5. Membrane-bound organelles such as Mitochondria, Plastids, E.R, Goliapparatus, Lysosomes, Peroxisome, etc., are present.
6. Cell division occurs by meiotic cell division.
Question 3. What would happen if plasma membrane ruptures or breaks down?
Ans.3) Plasma membrane is a selectively permeable membrane of the cell that maintains it homeostasis,i.e, constant internal composition of the cell. If it ruptures or break downs the constant internal chemical composition of the cell will be lost and it will not be able to perform its basic functions. Such a cell with ruptured plasma membrane is killed.
Question 4. What would happen if plasma membrane is ruptures or break down?
Ans.4) There would not be any lysosome for intracellular digestion and cleansing, non complexing of molecules, no exocytosis and no formation of new plasma membrane.
Question 5. Which organelle is known as the power house of the cell? Why?
Ans.5) Mitchocondria is known as the power house of the cell as it contains some digestive enzymes that are needed for proper oxidation of the food stuffs present in the cell to Co2 and water. Oxidation of food releases energy which is released in the form of AP molecules. These ATP molecules are used as cellular fuel in the cell. Energy stored in ATP is used to bring about energy-requiring activities of cell such as photosynthesis, protein synthesis and muscle contraction.
Question6. Where do the lipids and proteins constituting the cell membrane get synthesized?
Ans.6) Proteins are synthesized in ribosomes of rough E.R while lipids are synthesized over smooth E.R.
Question 7. How does an Amoeba obtain its food?
Ans.7) Amoeba is a unicellular animal. It acquires its food by the process of endocytosis. Plasma membrane of amoeba is flexible with its help amoeba engulf food practices. The engulfed food passes into the body of organism as a phagosome. Phagosome combines with to produce digestive or food vacuole. Digestion occurs in food vacuole. The digestion food passes into cytoplasm. The undigested matter is thrown out of the cell.
Question 8. What is osmosis?
Ans.8) Osmosis is diffusion of water from the region of higher concentration to the region of lower concentration through a semi-permeable membrane.
Question 9. 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 into a trough containing water.
- Keep cup ‘A’ empty,
- Put one tea spoon sugar in cup ‘B’;
- Put one tea spoon salt in cup ‘C’;
- Put one tea spoon sugar in boiled potato cup ‘C’.
Keep these for two hours. Then observe the four potato cups and answer the following:
(i) Explain why water gets in the hollowed portion of ‘B’ and ‘C’.
(ii) Why is potato ‘A’ necessary for this experiment?
(iii) Explain why water does not gather in the hollow out portion of ‘A’ and ‘D’.
Ans.9) (i) When unboiled potato cup were put into a throw containing Water, the cells of potatoes gained water by endosmosis When a teaspoon of sugar and salt were added later in the hollowed portion of B and C cups respectively, water movement occurred through the plasma membranes of the cells frown within the cells of potato into the hollowed portion of both B and C cups because of exosmosis (i.e, exit of water molecules through permeable plasma membranes from within the cellos of uncoiled potatoes into the hollowed portions having hypertonic sugar and salt, respectively).
(ii) Potato Cup A is necessary in the experiment as a control for providing comparison with situations created in potato cups B, C and D. It indicates that the potato cavity alone does not induce movement of water.
(iii) Water does not gather in the hollowed portion of potato cop A because it does not possess higher osmotic Concentration than the cells the cells of potato.
Potato cup D is boiled potato cup. On boiling, potato cells die and the membranes of the potato cells lost their permeability As a result, when teaspoon of sugar is added into the hollowed portion of boiled potato cup D, water does not come out from within the potato cells into the hollowed portion.
For notes of chapter 5/ The Fundamental and Structural Unit of Life: Cell, CLICK ON THE LINK BELOW