NCERT Solutions for Class 9 Science Chapter 5 The Fundamental Unit Of Life

Q1 ) Make a comparison and write down ways in which plant cells are different from animal cells.

Answer :

Q2 ) How is prokaryotic cell different from a eukaryotic cell?

Answer :

Q3 ) What would happen if the plasma membrane ruptures or breaks down?

Answer :

If plasma membrane ruptures or breaks down then the inner content of the cell containing cytoplasm and different organelles will get exposed to the outer environment, thus becoming prone to damage and infection and ultimately leading to cell death.

Q4 ) What would happen to the life of a cell if there was no Golgi apparatus?

Answer :

The absence of Golgi apparatus will be disable the cells from packing and dispatching materials that are produced by the cells.

Golgi apparatus is the organelle which produces lysosome which is the suicide bag of the cell.

Without lysosome, the invaded damaged cells cannot protect the nearby healthy cells from getting infected and the whole infection and destruction will rapidly damage every organs and organ systems, thus resulting in the failure of vital mechanisms and functions, leading to the death of an organism.

Q5 ) Which organelle is known as the powerhouse of the cell? Why?

Answer :

Mitochondria is known as the powerhouse of the cell because it produces ATP (Adenosine triphosphate) which is the energy currency of the cell as it provides energy to the cell, thus helping it to perform every cellular metabolism and coordinate the functions in different tissues, organs and organ systems.

Q6 ) Where do the lipids and proteins constituting the cell membrane get synthesised?

Answer :

Lipids and proteins are synthesized in the ER [Endoplasmic Reticulum].

Lipids are synthesized by smooth endoplasmic reticulum which is also called as SER.
Proteins are synthesized by rough endoplasmic reticulum which is also called as RER. Proteins are synthesized by the ribosomes that are attached to the RER.

Q7 ) How does an Amoeba obtain its food?

Answer :

Amoeba obtain its food by cell membrane which helps in the formation of the food vacuole. The food vacuole will contain the food items that the amoeba had ingested with the help of pseudopodia.

Q8 ) What is osmosis?

Answer :

The process of movement of water molecules from a region of higher concentration to a region of lower concentration through a semipermeable membrane is known as osmosis.

Osmosis takes place only after the formation of concentration gradient in case of liquids.

Q9 ) 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 will accumulate in the hollowed portions of B and C as a result of difference in the water concentration, due to which a concentration gradient forms and thus water from higher concentration (from the trough containing water) flows to a region of lower water concentration (hollowed portion of potato cups). This is a result of osmosis of water in a hypotonic solution.

(ii) Potato cup A is essential in this experiment as it is a significant reference to compare different scenarios seen in potato cups B, C and D.

(iii) Potato cup A didn't show any change in the concentration because it is an example of isotonic solution. Potato cup D is a boiled potato which tells us that this potato has same or more water concentration than the trough containing water in which potato cup D is placed. So there is no flow of water from the trough into the hollow portion of potato cup D.

Q10 ) Which type of cell division is required for growth and repair of body and which type is involved in formation of gametes?

Answer :

Mitosis is the type of cell division which is required for growth and repair of body.
Mitosis is a type of equational division which can help in the generation of new cells and in their formation into the tissues which was destroyed at the site of injury in the body of the organism. In this case, if meiosis will take place, then it cannot supply more cells to the site of injury, thus resulting in the loss of blood and this will ultimately lead to the death of the organism.

Meiosis is the type of cell division which is involved in formation of gametes.
Meiosis is a type of reductional division which produces cell by reducing the number of chromosomes in them into half. In the gamete cell, if the gamete will contain full chromosomes due to mitosis, then at the time of fertilisation, when two gamete fuses (male gamete fuses with female gamete), then the chromosome number in the offspring will be doubled as compared to their parents, thus causing imbalance. But if each gamete will carry half the chromosomes, then the offspring will have the same number of chromosomes as that of their parents.