Topic outline

    • The Fundamental Unit Of Life

      Q70. Draw a neat labelled diagram of a plant cell.

      Ans.


       Image from NCERT 

       

      Q71. Draw a neat labelled diagram of an animal cell.

      Ans. 


      Image from NCERT 

       

      Q72. If cells of onion peel and RBC are separately kept in hypotonic solution, what among the following will take place? Explain the reason for your answer.

      (a) Both the cells will swell.

      (b) RBC will burst easily while cells of onion peel will resist the bursting to some extent.

      (c) Both ‘a’ and ‘b’ are correct.

      (d) RBC and onion peel cells will behave similarly.

      Ans. (c) Both ‘a’ and ‘b’ are correct.

      Explanation:

      Cells of onion peel are surrounded by a cell wall whereas the RBCs (red blood cells) do not have cell wall. When the cells of onion peel and RBCs are separately kept in hypotonic solution, RBC will burst as there is no mechanism to resist entry of water into them but onion peel cells do not burst. Endosmosis causes some initial swelling in such onion peel cells but cell wall puts a mechanical barrier to promote entry of water and thus, these cells do not burst.

       

      Q73. Match the following:

      A

      B

      (a)

      Smooth endoplasmic reticulum

      (i)

      Amoeba

      (b)

      Lysosome

      (ii)

      Nucleus

      (c)

      Nucleoid

      (iii)

      Bacteria

      (d)

      Food vacuoles

      (iv)

      Detoxification

      (e)

      Chromatin material and nucleolus

      (v)

      Suicidal bag

       

      Ans. 

      A

      B

      (a)

      Smooth endoplasmic reticulum

      (i)

      Amoeba (d)

      (b)

      Lysosome

      (ii)

      Nucleus (e)

      (c)

      Nucleoid

      (iii)

      Bacteria (c)

      (d)

      Food vacuoles

      (iv)

      Detoxification (a)

      (e)

      Chromatin material and nucleolus

      (v)

      Suicidal bag (b)

       

      Q74. What would happen to the life of a cell if there was no Golgi apparatus? 

      Ans. The material synthesised near the ER is packaged and dispatched to various targets inside and outside the cell through the Golgi apparatus. Its functions include the storage, modification and packaging of products in vesicles. In some cases, complex sugars may be made from simple sugars in the Golgi apparatus. The Golgi apparatus is also involved in the formation of lysosomes. 

      Without the Golgi apparatus, the cells will be disabled from packaging and dispatching materials that were produced by the cells. The Golgi apparatus is also involved in the formation of lysosomes. Hence, in the absence of Golgi apparatus, lysosomes will not be produced.

       

      Q75. Differentiate between rough and smooth endoplasmic reticulum. How is endoplasmic reticulum important for membrane biogenesis?

      Ans. 

      Rough endoplasmic reticulum

      Smooth endoplasmic reticulum

      1. Ribosomes are attached to the outer surface of its membrane.

      1. It does not contain ribosomes.

      2. It is specialized to synthesize proteins.

      2. It is specialized to synthesize lipids and fats.

       

      There are two types of ER– rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER). RER looks rough under a microscope because it has particles called ribosomes attached to its surface. The ribosomes, which are present in all active cells, are the sites of protein manufacture. The manufactured proteins are then sent to various places in the cell depending on need, using the ER. The SER helps in the manufacture of fat molecules, or lipids, important for cell function. Some of these proteins and lipids help in building the cell membrane. This process is known as membrane biogenesis.

       

      Q76. 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. 

      Ans. (i) In the above experiment, when unboiled potato cups B and C were put in a trough containing water, the cells of potatoes gained water by endosmosis but when a teaspoon of sugar and salt is added in the hollowed portion cup B and cup C respectively, water movement occurred through plasma membrane of the cells of potato into the hollowed portion of both B and C cups because of exosmosis.

      (ii) Potato A is necessary for this experiment for comparison, it acts as a control. It indicates that the potato cavity alone does not induce movement of water.

      (iii) Water does not gather in the hollowed out portion of A, as cup of A does not have change in the concentration for water to flow. 

      Potato cup D is boiled potato cup. On boiling, potato cells die and the membranes of the potato cells lost their permeability. Thus, water does not come out from within the potato cells into the hollowed portion.

       

      Q77. In brief state what happens when

      (a) Dry apricots are left for some time in pure water and later transferred to sugar solution.

      (b) A red blood cell is kept in concentrated saline solution.

      (c) The plasma membrane of a cell breaks down.

      (d) Rheo leaves are boiled in water first and then a drop of sugar syrup is put on it.

      (e) Golgi apparatus is removed from the cell.

      Ans. (a) When placed in pure water, dry apricot swell up due to endosmosis and when they are kept in sugar solution, they shrink due to exosmosis.

      (b) In concentrated salt solution, red blood cells shrink and give a shriveled appearance.

      (c) Breakdown of plasma membrane will result in death of the cell as protoplasmic structures will get dispersed.

      (d) Boiling shall kill the leaves. The dead leaves and their cells do not undergo plasmolysis.

      (e) Its functions include the storage, modification and packaging of products in vesicles. In some cases, complex sugars may be made from simple sugars in the Golgi apparatus. The Golgi apparatus is also involved in the formation of lysosomes. Thus, if Golgi apparatus is removed from the cell, then functions carried out by Golgi will also not take place, resulting in non-functioning and hence death of the cell.