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Class 9 chapter 5 science notes |
The fundamental unit of life class 9 important questions and answers
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Chapter 5 The fundamental unit of life notes class 9
Question 1: Make a comparison to write down ways in which plant cells are different from animal cells.
Answer: The cells of animals and plants have the following differences:Plant Cell
1.Plant cells are larger than animal cells.
2. The plasma membrane of plant cells is surrounded by a rigid cell wall of cellulose.
3.Plastids are present.
4. Most mature plant cells have a permanent and large central sap vacuole.
5. Plant cells have many simpler units of Golgi apparatus, called dictyosomes.
6. Plant cells lack centrosome and centrioles.
Animal cell
1. Animal cells are generally 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 cells have a single highly complex and prominent Golgi apparatus.
6. Animal cells have centrosome and centrioles.
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Question 2: How is a prokaryotic cell different from a eukaryotic cell?
Answer: Difference between prokaryotic cell and eukaryotic cell:Prokaryotic Cell
1. Cell size 1s generally small (1-10 nm)2. Nuclear region ts called nucleoid and is not surrounded by a nuclear membrane.
3. Only a single chromosome is present.
4. Nucleolus is absent
5. Membrane bound cell organelles are absent.
6. Cell division by fission or budding no mitosis.
Eukaryotic Cell
1.Cell is generally large (5 - 100 nm).2. Nuclear material is surrounded by a nuclear membrane.
3. More than one chromosome is present.
4. Nucleolus is present.
5. Membrane bound cell organelles.
6. Cell division mitotic or meiotic.
Chapter 5 science class 9 question answer | The fundamental unit of life class 9 pdf |
Question 3: What would happen if the plasma membrane ruptures or breaks down?
Answer: Plasma membrane provides a container for the cell organelles and cytoplasm. Moreover, plasma membrane also protects the contents of a cell from external environment. In case the plasma membrane ruptures or breaks down, the cell contents would be exposed to the external environment. This would prove lethal for the cell and the cell would cease to exist .Question 4; What would happen to the life of a cell if there is no Golgi apparatus?
Answer: Golgi apparatus plays the important role of packaging various substances for further use or for storage. If there was no Golgi apparatus, various substances would not be in a position to be transformed in proper forms for further use. Certain substances; like protein and lipid are important for the formation of plasma membrane and hence absence of Golgi apparatus will hamper the formation of new cells during cell division.Question 5: Which organelle is known as the powerhouse of the cell? Why?
Answer: Mitochondria are known as the powerhouse of cells. Mitochondria create energy for the cell, and this process of creating energy for the cell is known as cellular respiration. Most chemical reactions involved in cellular respiration occur in the mitochondria. The energy required for various chemical activites needed for life is released by the mitochondria in the form of ATP (Adenosine triphosphate) molecules. For this reason, mitochondria are known as the powerhouse of cells.Raed Also notes : Class 9 Geography
Extra questions for class 9 science chapter 5 with answers
Question 6: Where do the lipids and proteins consistuting the cell membrane get synthesised?
Answer: Lipids are synthesized in the endoplasmic reticulum. Protein is synthesized in ribosomes which are usually present on the rough ER.Question 7: How does Amoeba obtain its food?
Answer: Amoeba obtains its food through a process called phagocytosis. The cell membrane of amoeba is projected into numerous finger-like outgrowths; called pseudopodia. Amoeba surrounds a food particle by pseudopodia and makes a food vacuole; after engulfing the food.Question 8: What is osmosis?
Answer: The process of movement of a water molecule from a region of higher concentration to a region of lower concentration through a semipermeable membrane is known as osmosis.The fundamental unit of life class 9 notes | The fundamental unit of life question and answer |
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 in a trough containing water. Now,(a) Keep cup A empty
(b) Put one teaspoon sugar in cup B
(c) Put one teaspoon salt in cup C
(d) 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:
(i) Explain why water gathers 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 hollowed out portions of A and D.
Answer:
(i) Water gathers in the hollowed portions of set-up B and C because water enters the potato as a result of osmosis. Since the medium surrounding the cell has a higher water concentration than the cell, the water moves inside by osmosis. Hence, water gathers in the hollowed portions of the potato cup.
(ii) Potato A in the experiment acts as a control set-up. No water gathers in the hollowed portions of potato A.
(iii) Water does not gather in the hollowed portions of potato A because potato cup Ais empty. It is a control set-up in the experiment.
Water is not able to enter potato D because the potato used here is boiled. Boiling denatures the proteins present in the cell membrane and thus, disrupts the cell membrane. For osmosis, a semi-permeable membrane is required, which is disrupted in this case. Therefore, osmosis will not occur. Hence, water does not enter the boiled potato cup.
Question 10: Which type of cell division is required for growth and repair of body and which type is involved in formation of gametes?
Answer: There are two ways in which a cell divides:a)Mitosis
b)Metosis
Mitosis is the type of cell division that is involved in the growth and repair of body whereas metosis is a type of cell division which results in the formation of gametes.
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