Chapter 5

Fundamental Unit Of Life

Intext questions

Page # 59

1. Who discovered cell and how?
Ans: Robert Hooke discovered cell.  He observed a thin slice of Cork under primitive microscope and observed small compartments which named as cells.

2. Why is the cell called the sitter and functional unit of life?
  • All living organisms are made up of cells.
  • All the life processes are cast diversion, respiration, excretion etc., are carried out in the cell.
Page #61 

1. How do substances like carbon dioxide and water move in and out of cells? Discuss.
Ans: Moment of carbon dioxide takes place from the region of its high concentration to the region of low concentration by diffusion.
Movement of water molecules takes place from the region of its high concentration to low concentration through the semipermeable membrane by osmosis.

2. Why is the plasma membrane called a selectively permeable membrane?
Ans: Plasma membrane regulates the entry and exit of selected substances inside and outside the cell so it is called selective permeable.

Page # 63
  1. Fill in the gaps in the following table illustrating the difference between prokaryotic and eukaryotic cells 

Prokaryotic cells

Eukaryotic cells 

1. Size: Generally small (1-10 μm)

           1 μm = 10-6m


generally large [5 – 100 μm ]

2. Nuclear region not well defined and nucleus is not bound by a nuclear membrane and it is known as nucleoid. 

A nuclear region well defined and surrounded by a nuclear membrane. 

3. Chromosome single. 

more than one chromosome.

4. Membrane-bound cell organelles absent. 

Membrane-bound cell organelles are present. 

Page no #65

1. Can we name the two organelles we have studied that contain their own genetic material?
Ans:  Plastids, Mitochondria.

2. If the organization of a cell is destroyed due to some physical or chemical influences, what will happen?
Ans: In this situation, the contents of the cell will come out and the shell will die.

3. Why are lies also known as suicide bags?
Ans: Lysosomes contain powerful digestive enzymes. During any disturbance in cellular metabolism, lies also burst and enzymes released digest their own self will stop so they are called suicide bags.

4. Where are proteins synthesized inside the cell?
Ans:  Ribosomes are the site of protein synthesis.

Exercises question and answer

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

Plant cellsAnimal cells
The animal cell does not have cell wall. It has only plasma membrane.Plant cells have cell wall made up of cellulose.
The cytoplasm is a denture, more granular and occupies most of the space.The cytoplasm is at the periphery and from a thinner layer in a large cells.
Vacuoles are absent. If present they are small and help in excretion secretion.Vacuoles are large and occupy the entire cell.
Plastids are absent.Plastids are present such as leucoplast, chromoplast, chloroplasts.
Centrosomes are present.Centrosomes are absent.
They are usually smaller in size.They are usually bigger in size.
Golgi bodies are presented.Dictyosomes much are present.

2. How is prokaryotic cell different from eukaryotic cell?

Prokaryotic cell

Eukaryotic cell 

It is a primitive cell, generally small in diameter. 

It is an advanced self, generally big. 

The nucleus does not have a nuclear membrane. 

The nucleus has a nuclear membrane. 

Nucleolus is absent. 

Nucleolus is present.

Chromosome is single circular and in direct contact with cytoplasm. 

Many linear chromosomes are present in the nucleus of the cell. 

The membrane-bound cell organelles are not present. 

The membrane-bound cell organelles are present and well developed. 

Cell organelles like mitochondria, plastids, endoplasmic reticulum are absent. 

mitochondria, plastids, endoplasmic reticulum golgi bodies are present. 

Cell division by budding or fusion. 

Cell division by meiosis 

Prokaryotes are bacteria and cyanobacteria. 

Eukaryotes are cell of plant and animal body amoeba. 

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

Ans:  If the organism of a cell is destroyed due to some physical or chemical influences, the contact of cell will come out, as it protected by a cell membrane.

3. What would happen to the life of cell if there was no golgi apparatus?
Ans: The life of a cell would be impossible as the golgi apparatus performs several functions needed for the cell to live. Some of the functions are secretion of enzymes, proteins, etc., a packing it in small vessels are bags, the formation of the cell wall, complex sugar from simple sugar.

4. Which organelle is known as the powerhouse of the cell? Why?
Ans: Mitochondria
Mitochondria is the site of cellular respiration or oxidation of food. As a result of it, energy is released, which is stored and packed as ATP [Adenosine triphosphate). Whenever energy is needed by the shell, the stored ATP is used. As mitochondria generates energy as ATP, it is called the powerhouse of the cell.

5. Where do the lipids and proteins consisting the cell membrane get synthesized?
Ans:  Endoplasmic Reticulum [ER]
6. How does an Amoeba obtain its food?
Ans:  An amoeba obtains this food by forming a foot vacuole. The amoeba gives out two finger-like projections in the same direction which moves forward and covers the food in vacuole after joining at the tip.
  • Formation of pseudopodia.
  • Converting the food.
  • Joining of pseudopodia.
  • Formation of the food vacuole.

7. What is osmosis?
Ans: The moment of water molecules from a region of higher concentration to a region of lower concentration through a semi-permeable membrane is called osmosis.

8. Carryout 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 the cup 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)   Water accumulates in the hollowed portions of B and C as a difference in the water concentration is observed. Thereby, endosmosis occurs as the cells act as a semipermeable membrane.

(ii) Potato A is essential in this experiment as it is significant to compare different scenarios seen in potato cups B, C, and D. The potato A in this experiment clearly shows that the potato cavity on its own, cannot bring about water movement.

(iii) Cup in A does not show any change in the water flow concentration for osmosis to occur, which requires the concentration to be higher than the other. Cells in cup D are dead, thus there is no existence of a semipermeable membrane for water flow. Consequently, osmosis does not occur.

Important points 

  • Cells are living on half-life.
  • The cell has a special component called organelles.  
  • 3 features in almost every cell plasma membrane nucleus and cytoplasm. 
  • Cell member is a semi-permeable
  • Osmosis is the moment of water molecules from a region of each high concentration to the region of its low concentration throughout the semipermeable membrane. 
  • Plant cell, in addition to the plasma membrane, have another rigid outer covering called the cell wall.