Chapter-5 THE FUNDAMENTAL UNIT OF LIFE

 1. Who discovered cells, and how? 

Explanation:

 The word cell come from latin word Cellula which means " Little Compartment". In 1665, Robert Hooke discovered cells, while studying a thin slice of cork he saw that cork resembled to the structure of honey comb consisting of many little compartment.


2.  Why is the cell called the structural and functional unit of life?

Explanation:

The cell called the structural and functional unit of life because, a cell is capable of independently carrying out all the necessory activities like, Respiration, Digestion, Excretion etc. So Cell is called the functional unit of life.

Structure unit because all organisms are made up of cell ( group of tissues).


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

Explanation:

CO2 moves by the process of Diffusion, The Concentration of CO2 is high in the cell. This Difference Concentration level causes CO2 to move From Higher Concentration to the outside.Osmosis is the movement of water molecules from the side of their higher concentration to lower concentration through semi permeable untill equilibrium is reached.


4. Why is the plasma membrane called a selectively permeable membrane?44

Explanation:

Plasma Membrane is called selectively permeable membrane as it permits the materials to move in and out of the cell. Not all materials are free to move in and out of the cell.


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

Explanation:

The two organelles which have their own genetic material are Mitochondria and Plastid.


6.  If the organisation of a cell is destroyed due to some physical or chemical influence, what will happen?

Explanation:

When there is any damage to the cell and repair is not possible, then Lysosome burst and digest their own cell with the help of their enzymes. Thats's why Lysosome are known as Suicidal bag of the cell.


7.  Why are Lysosomes known as suicide bags?

Explanation:

 If there is any damage to the cell and repair is not possible, then lysosome burst and their enzymes digest the cell. That's why Lysosome are known as Suicide bags.


8. Where are proteins synthesised inside the cell?

Explanation:

Proteins are synthesised in Ribosomes. Hence, Ribosomes are also celled protein factory. Ribosomes are found in cytoplasm as well as attached to the Rough Endoplasmic Reticulum.


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

Explanation:

 Plant Cells

(i) Cell Wall Is present.

(ii) They have chloroplast.

(iii) They do not have Centriole.

(iv) Vacuole is large and present in centre.

(v) Nucleus is present in the side in plant cell.

Animal Cells

(i) Cell wall is absent.

(ii) They do not have chloroplast.

(iii) Centriole is present.

(iv) Vacuole is small.

(v) Nucleus is present in the centre.


10. How is prokaryotic cell different from a eukaryotic cell?

Explanation:

  Prokaryotic Cell

(i) Size of cell is generally small.

(ii) Nucleus is Absent.

(iii) Centrioles are Absent.

(iv) Small Ribosomes.

(v) It contains single chromosome.

Eukaryotic Cell

(i) Size of the cell is large.

(ii) Nucleus is Present.

(iii) Centrioles are Present in animal cells.

(iv) Large Ribosomes.

(v) It contains more than one chromosome.


11. What would happen if the plasma membrane ruptures or breaks down?

Explanation:

 Plasma membrane is also called selectively permeable membrane.Because it controls the movement of substance or materials to and from the cell. if plasma membrane ruptures or breakdown, then susbtance will move freely in and out of the cell. Consequently the cell will die due to disappearance of protoplasmic material.


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

Explanation:

Golgi apparatus has the function of storage, modification and packaging of materials in vesicles.

(i) If there are no golgi apparatus then packaging and dispatching of materials synthesised by the cells would be stocked.

(ii) Golgi Apparatus also helps in the formation of new cell, hence in the absence of golgi apparatus new cells would not form.


13. Which organelle is known as the powerhouse of the cell? Why?

Explanation:

Mitochondria is known as powerhouse of the cell, it is because it releases the energy required for different activities of life in the form of ATP ( Adenosine Tri-Phosphate).


14.  Where do the lipids and proteins constituting the cell membrane get synthesised?

Explanation:

There are two types of endoplasmic reticulum.

(i) Rough Endoplasmic Reticulum (RER)

(ii) Smooth Endoplasmic Reticulum (SER) 

Proteins are synthesised in Rough Endoplasmic Reticulum. And Lipids are synthesised in Smooth Endoplasmic Reticulum.


15. How does an Amoeba obtain its food?

Explanation:

Endocytosis is a process in which substance are brought into the cell. Amoeba obtain it's food by the process of endocytosis. In this process Amoeba takes it's food by the cell membrane forming food vacuole. Amoeba secretes digestive enzymes for the digestion of engulfed particle. After digestion, digested food is absorbed and undigested is thrown out of the body.


16.  What is osmosis?

Explanation:

Osmosis can be defined as the spontaneous flow of the solvent molecules towards the solution side when both are seperated by the semi permeable membrane.


17. 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.

Explanation:

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

(i) Water gathers in hollowed portion of B&C due to concentration gradient

endosmosis occurs. Cells of Potato acts as semi permeable membrane.

(ii) A is necessory beacuse it is used to different scenarios seen in cup B,C & D

(iii)  In A there is no concentration gradient while in potato cup D, the cell are dead. Therefore, water does not gather in A and D. 


18.  Which type of cell division is required for growth and repair of body and which type is involved in formation of gametes?

Explanation:

Mitosis is a type of cell division that is require for the growth and repair of body.

Meiosis is a type of cell division that is involved in formation of gametes.