CHAPTER 5, THE FUNDAMENTAL UNIT OF LIFE
Page.no-59
1-Who discovered cells, and how?
Ans-Robert Hooke discovered cells. He examined a slice of cork and found its structure resembled with the structure of honeycomb which is made of separate units.He studied it through a self-designed microscope and called these separate unit cells.
2-Why is the cell called the structural and functional unit of life ?
Ans-Cells are basic building blocks of the body of all living organism,some of the organism are unicellular and some of them are multicellular. All body parts are made of different cells .A body part is made of similar kind of cells have same function.A cell has organells to perform a particular type of function.The function of a body part depends on the cells it is made up of,it is that’s why cell is a structural and functional unit of life.
Page.no-45
1-How do substance like CO2 and water move in and out of the cell ? Discuss.
Ans- Due to the process of respiration following reaction occurs inside the cell
C6H12O6 + O2 = CO2 + H2O + energy(ATP)
The concentration of CO2 becomes more inside the cell in comparision of the surrounding of the cell and thus CO2 moves from inside to outside of the cell due to the process of diffusion and because concentration of O2 is greater outside of the cell comparission to inside of cell it moves from outside to inside of the cells through the process of diffusion. Plasma membrane of cell is a permeable membrane ,the water transports from high concentration to low concentration through plasma membrane by the process of osmosis.
2.Why is the plasma membrane called a selectively permeable membrane ?
Ans. The plasma membrane is called semi permeable membrane because it allows to enter few selected substances to inside and outside of the cell through the process of diffusion and osmosis depending on the concentration of materials in the regions.
CBSE 10 Class science NCERT solution of"Life Process"
CBSE 10 Class science NCERT solution of"Life Process"
Page.no-3
1-Fill up the gaps in the following table illustrating the differences between prokaryotic and eukaryotic cells.
Prokaryotic cell
|
Eukaryotic cell
|
||
1
|
Size: generally small (1 to 10μm) 1 μm = 10-6m
|
1
|
Size:generally large(5-100μm)
|
2
|
Nuclear region:
………………………………………………………….
And is known as ……………..
|
2
|
Nuclear region:well- defined and surrounded by nuclear membrane.
|
3
|
Chromosome :single
|
3
|
More than one chromosome
|
4
|
Membrane –bound cell organell are absent
|
4
|
……………………………………….
|
Ans-
Prokaryotic cell
|
Eukaryotic cell
|
||
1
|
Size: generally small (1 to 10μm) 1 μm = 10-6m
|
1
|
Size:generally large(5-100μm)
|
2
|
    Nuclear region : Poorly defined because of the absence of a nuclear membrane and is known as nucleoid. |
2
|
Nuclear region:well- defined and surrounded by nuclear membrane
|
3
|
Chromosome : single
|
3
|
More than one chromosome
|
4
|
Membrane bound cell organells are absent
|
4
|
    Membrane bound cell organells are present such as mitochondria, plastids etc are present. |
1-Can you name the two organells we have studied that contain their own genetic material ?
Ans- Mitochondria and plastids are the two organells that contain their own genetic material(DNA and ribosomes).
2- If the organization of a cell is destroyed due to some physical or chemical influence,what will happen ?
Ans-If the organization of a cell is destroyed due to some physical or chemical influence then cell will not be able to perform its basic functions like respiration, excreation and absorbtion of nutrition and as a result of this our body part will not work and even it may result to death.
3-Why are lysosomes are known as suicidal bag ?
Ans- Lysosomes are membrane bound vascular structure.Lysosomes releases powerfull digestive engymes, it breakdown any food particles entering into it. Sometimes , lysosomes can cause self-distruction of any cell by the release of such engymes within the cells, Hence these are also known as ‘suicidal bags’.
4-Where are protein synthesized inside the cell ?
Ans- Ribosomes are the sites for protein synthesis. Ribosomes are very small in structures found either in free states suspended in cytoplasm or attached to the surface of endoplasmic raticulam.These are composed of ribonucleic acid and protein.
1-Make a comparison and write down ways in which plant cells are different from animal cells.
Ans-
2.How is a prokaryotic cell different from a eukaryotic cell?
Ans-
Prokaryotic cell - Most prokaryotic cells are unicellular. Size of cell is generally small(0.5 - 5μm). Nuclear region is poorly defined due to absence of nuclear membrane. It contains single chromosome. Nucleolus is absent. Cell organells like golgi apparatus, endoplasmic ratticulam,plastids, mitochondria etc are absent. Cell division occurs by mitosis. Prokaryotic cell is found in bacteria and blue green algae.
Eukaryotic cell- Most eukaryotic cells are multicellular. Size of cell is generally large (50 – 100 μm). Nuclear region is well defined and is surrounded by nuclear membrane. It contains more than one chromosome. Nucleolus is present. Cell organells like golgi apparatus, endoplasmic ratticulam,plastids, mitochondria etc are present. Cell division occurs by mitosis and meosis. Eukaryotic cell is found in fungi, plants and animal cells.
3-What would happen if plasma membrane ruptures or break down ?
Ans-If the plasma membrane of the cell is ruptured , then the cell will die because the plasma membrane regulates the movements of substances in and out of the cell through the plasma membrane by the process of diffusion and osmosis. Thus if plasma membrane ruptured, then the cell will leak out its contents.
4-What would happen to the life of a cell if there was no golgi apparatus ?
Ans-If there was no golgi apparatus in the cell then activities performed by golgi apparatus will not take place.
(i)-Membrane of golgi apparatus is often connected to ER membrane. It collects simple molecules and combines them to make more complex molecule. These are then packaged in small vasicles and either stored in the cell or sent out as per the requirement.Thus if golgi apparatus is absent in the cell , then the above process of storage , modification and packaging of products will not be possible.
(ii)-The formation of complex sugar from simple sugar will not be possible as this takes place with the help of engymes present in the golgi apparatus.
(iii)-The golgi apparatus is involved in the formation of lysosomes or peroxisomes . Thus if golgi apparatus is absent then the synthesis of lysosomes or peroxisomes will not be possible in the cell.
5- Which cell organell is known as the power house of the cell ? why ?
Ans- Mitochondria is known as the power house of the cell because it releases energy which is required for all chemical reaction occurs in our body. It releases energy as a result of cellular respiration inside the cell in the form of ATP(Adenosine triphosphate).
6- Where do the lipids and protein constituting the cell membrane get synthesized ?
Ans-Lipids and protein constituting the cell membrane are synthesized in the endoplasmic raticulam.
SER (smooth endoplasmic raticulam) helps in the manufacturing of lipids.
RER (Rough endoplasmic raticulam) has particles attached to its surface is known as ribosomes. These ribosomes are the site for protein synthesis.
7-How does an Amoeba obtain its food ?
Ans-Amoeba obtains its food through the process of endocitosis.The flexibility of the cell enables the cell to engulf solid food particles and other material from its external environment.
8-What is osmosis ?
Ans- The flow of liquid from higher concentration to lower concentration through a permeable membrane is known as osmosis.As an example if the concentration of water outside of the cell is more in comparison of the concentration of water inside of the cell then flow of water will be from outside to inside of the cell .
9- Carry out 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 tea spoon sugar in cup B
(c) Put one tea spoon salt in cup C
(d) Put one tea spoon sugar in the boiled potato cup D
Keep these for two hours then observe the four potatoes cup 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 portion of A and B.
Experimental set up
(i)Water gathers in the hollowed portion 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 the process of osmosis.Hence water gathers in the hollowed portion of the cup.
(ii)Potato A in the experiment acts as a control set-up. No water gathers in the hollowed portion of potato A.
(iii)Water does not gather in the hollowed portion of potato A because potato cup A is empty.It is a control set-up in the experiment.Water is not able to enter potato D because potato D here is boiled . Boiling disrupts the cell membrane. For osmosis semi permeable membrane is required,which is disrupted in this case. Therefore osmosis will not occur and water will not enter the boiled potato.
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