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5. The Fundamental Unit of Life

Chapter Review

5. The Fundamental Unit of Life

Text-book Questions

​Textual Questions With solution

Page No: 59

Q1. Who discovered cells and how?

Solution:

An English Botanist, Robert Hooke discovered cells. In 1665, he used self-designed microscope to observe cells in a cork slice.

Q2. Why is the cell called the structural and functional unit of life?​

Solution:

Cells are called the structural and functional unit of life because all the living organisms are made up of cells and also all the functions taking place inside the body of organisms are performed by cells.

Page No: 61

Q1. How do substances like CO2 and water move in and out of the cell? Discuss.

​Solution:

The substances like CO2and water move in and out of a cell by diffusion from the region of high concentration to low concentration. When the concentration of CO2and water is higher in external environment than that inside the cell, CO2and water moves inside the cell. When the concentration outside the cell becomes low and it is high inside the cell, they moves out.

Q2. Why is the plasma membrane called a selectively permeable membrane?

Solution:

Plasma membrane called a selectively permeable membrane because it regulates the movement of substances in and out of the cell. This means that the plasma membrane allows the entry of only some substances and prevents the movement of some other materials.

Page No: 63

1. Fill in the gaps in the following table illustrating differences between prokaryotic and eukaryotic cells.

	Prokaryotic cell		Eukaryotic cell
1.	Size: generally small ( 1-10 µm) 1 µm== 10-6 m	1.	Size: generally large (5-100 µm)
2.	Nuclear region: ______________ and is known as ________.	2.	Nuclear region: well-defined and surrounded by a nuclear membrane
3.	Chromosome: single	3.	More than one chromosome
4.	Membrane-bound cell organelles are absent	4.	-------- ------ ------- ------- -------- ------

Solution:

	Prokaryotic cell		Eukaryotic cell
1.	Size : generally small (1-10 µm) 1 µm = 10-6​ m	1.	Size: generally large (5-100 µm)
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 a nuclear membrane
3.	Chromosome: single	3.	More than one chromosome
4.	Membrane-bound cell organelles are absent	4.	Membrane-bound cell organelles such as mitochondria, plastids, etc., are present

​Page No: 65

Q1. Can you name the two organelles we have studied that contain their own genetic material?

Solution:

Mitochondria and plastids

Q2. If the organisation of a cell is destroyed due to some physical or chemical influence, what will happen?
Solution:
If the organisation of a cell is destroyed due to some physical or chemical influence then cell will not be able to perform the basic functions like respiration, nutrition, excretion etc. This may stop all the life activities and may result in its death.

Q3. Why are lysosomes known as suicide bags?
Solution:
Lysosomes are called suicide bags because in case of disturbance of their cellular metabolism they digest their own cell by releasing own enzymes.

Q4. Where are proteins synthesized inside the cell?
Solution:
The proteins are synthesized in the Ribosome inside the cell.

Page No: 66 

 Exercise

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

Solution:

Animal cell	Plant cell
1. The do not have cell wall.	1. They have cell wall made up of cellulose.
2. They do not have chloroplast.	2. They contain chloroplast.
3. They have centrosome.	3. They do not have centrosome.
4. Vacuoles are smaller in size.	4. Vacuoles are larger in size.
5. Lysosomes are larger in number.	5. Lysosomes are absent or very few in number
6. Prominent Golgi bodies are present.	6. Subunits of Golgi bodies known as dictyosomes are present.

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

Solution:

Prokaryotic cell	Eukaryotic cell
1. Most prokaryotes are unicellular.	1. Most eukaryotes are multicellular.
2. Size of the cell is generally small (0.5- 5 µm).	2. Size of the cell is generally large (50- 100 µm).
3. Nuclear region is poorly defined due to the absence of a nuclear membrane or the cell lacks true nucleus.	3. Nuclear region is well-defined and is surrounded by a nuclear membrane, or true nucleus bound by a nuclear membrane is present in the cell.
4. It contains a single chromosome.	4. It contains more than one chromosome.
5. Nucleolus is absent.	5. Nucleolus is present.
6. Membrane-bound cell organelles such as plastids, mitochondria, endoplasmic reticulum, Golgi apparatus, etc. are absent.	6. Cell organelles such as mitochondria, plastids, endoplasmic reticulum, Golgi apparatus, lysosomes, etc. are present.
7. Cell division occurs through binary fission	7. Cell division occurs by mitosis.
8. Prokaryotic cells are found in bacteria and blue-green algae.	8. Eukaryotic cells are found in fungi, plants, and animal cells.

 

 

 

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

Solution:
If the plasma membrane ruptures or breakdown then the cell will not be able to exchange material from its surrounding by diffusion or osmosis. Thereafter the protoplasmic material will be disappeared and the cell will die.
Page No: 67
4. What would happen to the life of a cell if there was no Golgi apparatus?
Solution:
Golgi apparatus has the function of storage modification and packaging of the products. If there is no Golgi apparatus then the packaging and transporting of materials synthesized by cell will not happen.
5. Which organelle is known as the powerhouse of the cell? Why?
Solution:
Mitochondria are known as the powerhouse of cells because energy required for various chemical activities needed for life is released by mitochondria in the form of ATP (Adenosine triphosphate) molecules.
6. Where do the lipids and proteins constituting the cell membrane get synthesized?
Solution:
Lipids are synthesized in Smooth endoplasmic reticulum (SER) and the proteins are synthesized in rough endoplasmic reticulum (RER).
7. How does an Amoeba obtain its food?
Solution:
Amoeba takes in food using temporary finger-like extensions of the cell surface which fuse over the food particle forming a food-vacuole as shown in figure. Inside the food vacuole, complex substances are broken down into simpler ones which then diffuse into the cytoplasm. The remaining undigested material is moved to the surface of the cell and thrown out. 

8. What is osmosis?
Solution:
Osmosis is the process in which water molecules moves from the region of high concentration to a region of low concentration through a semi permeable membrane

5. The Fundamental Unit of Life

Additional -Questions

Nucleus – Nucleus is a largest cell organelle which consists inside the cell. Nuclei are found in all eukaryotic cells. It contains chromatin.

Cytoplasm –

Ribosomes : They are extremely small round bodies present either in free state in the cytoplasm.

Functions :

1.  it is responsible for synthesis of proteins from amino-acid.
2. They provide a surface for bio-chemical activities of the cell.                          

Q – Distinguish between plant and animal cell.

A –

Plant cell	Animal cell
It has cell wall. Chloroplast is present. Vacuoles are large in size. The process of photosynthesis occurs in it.	It has not cell wall. Chloroplast is not present. Vacuoles are mostly absent or present is very small size. The process of photosynthesis doesn’t occur in it.

 

Q – write the differences between prokaryotic cell and Eukaryotic cell.

prokaryotic cell	Eukaryotic cell
It is often small in size. Nucleus membrane is absent. It has one chromosome. There mostly cell organelles are absent.    Example. Yeast cell	It is often large in size. Nucleus membrane is present.  It has more than one chromosomes. There mostly cell organelles are present. Example: All multicellular organism.

Q – How does an Amoeba obtain its food?

A – Amoeba obtains its food by the process of endocytosis, in which it take food from outside by the help of its body surface. It encloses the food by plasma membrane. It engulfs the food and digest it.

Q – Why is plasma membrane is called selectivity permeable membrane?

A – The plasma membrane allows or permits the entry and exit of some material in and out of the cell, therefore it is called a selectivity permeable membrane.

Q – What is Osmosis?

A – Water also obeys the law of diffusion. The movement of water molecules through such a selectively permeable membrane is called Osmosis.

 

5. The Fundamental Unit of Life

Additional -Questions 2

Q-What is hypotonic solution?

A – if the medium surrounding the cell has a higher water concentration than the cell is known as hypotonic solution.

Q – What is Isotonic solution?

A – If the medium has exactly same water concentration than the cell is known as isotonic solution.

Q – What is hypertonic solution?

A – if the medium surrounding the cell has a lower concentration then the cell is known as hypertonic solution.

Q – Give three examples of organism in which the process of osmosis take place?

A – 1. Unicellular fresh water organism.

2. Plant cell tend to gain water through osmosis.

3. Absorption of water by plant roots is also an example of Osmosis.

Q – Why is cell called the functional and structural unit of body?

A – All living organisms are made of cells. Each living cell has ability to perform all basic functions. Which are the characteristics of all living organisms? It contained organelles work continues forever. Thus a group of cell that is similar in structure work together to achieve a particular function, Hence cell called the functional and structural unit of body.

Q – Name such two organelles which have their own genetic material like DNA and ribosomes.

A – in animal cells – Mitochondria.

       In Plant cells – plastid

Q – Where does the synthesis of protein occur in cell?

A – Mitochondria

Q – Why is mitochondria called the power house of cell?

A - The energy required for various chemical activities needed for life is released by mitochondria in the form of ATP (Adenosine triphopshate) molecules. ATP is known as the energy currency of the cell. The body uses energy stored in ATP for making new chemical compounds and for mechanical work. So mitochondria is called the power house of cell.

Q - Why are lysosomes known as suicide bags?

A – Due to disturbance in cellular metabolism When the cell gets damaged, lysosomes may burst and the enzymes digest their own dead cell. Therefore lysosomes known as suicide bags.

Q – What is cellulose? Where does it found?

A – cellulose is a natural polymer which is found in plant.

Q - Which is the longest cell of the body?

 A- Nerve  

Q – What is membrane biogenesis?

A - Some of these proteins and lipids help in building the cell membrane. This process is known as membrane biogenesis.

Q - If the organells of a cell is destroyed due to some physical or chemical influence, what will happen?

A – It resulting in damage of cell.

Q – What is chloroplast? Write its function.

A – chloroplast is coloured plastid it contained pigment chlorophyll. Chloroplasts are important for photosynthesis in plants. Chloroplasts also contain various yellow or orange pigments in addition to chlorophyll. It gives pigments to leaves steam, flower, and fruits.

Q – What is leucoplast? Write its functions.

A – leucoplast is white coloured plastid they are primarily organelles in which material such as starch,oils and protein granules are stored.

Q – what is the important role of specialized vacuoles in unicellular organism?

A – They play important role in expelling excess water and some wastes from the cell.  ​

5. The Fundamental Unit of Life

Assignment