Lakhmir Singh & Manjit Kaur Solutions: The Fundamental Unit of Life

 Page 1


 
1. Distinguish between prokaryotic and eukaryotic cells.
Answer 
Prokaryotic Eukaryotic 
Organisms are always unicellular Organisms are always unicellular and multicellular 
Nucleus is absent Nucleus is present 
Cell division takes place through binary fission Cell division takes place through mitosis 
DNA arrangement is circular DNA arrangement is linear 
Example: Bacteria, Blue-green algae Example: Plant and animal cell 
2. Write down the differences between organ and organelle.
Answer
Organ Organelle 
These are the parts of a body These are the parts of a cell 
These are found in multicellular organisms These are found in unicellular organisms 
These are macroscopic in nature These are microscopic in nature 
Example: Brain, Heart, Lungs Example: Cytoplasm, mitochondria 
3. Write down the differences between the nucleus and nucleoid.
Answer
Nucleus Nucleoid 
A nucleus is a membrane-bound structure in which 
eukaryotes store their genetic materials. 
Nucleoid is a particular area in which 
prokaryotes store their genetic materials. 
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1. Distinguish between prokaryotic and eukaryotic cells.
Answer 
Prokaryotic Eukaryotic 
Organisms are always unicellular Organisms are always unicellular and multicellular 
Nucleus is absent Nucleus is present 
Cell division takes place through binary fission Cell division takes place through mitosis 
DNA arrangement is circular DNA arrangement is linear 
Example: Bacteria, Blue-green algae Example: Plant and animal cell 
2. Write down the differences between organ and organelle.
Answer
Organ Organelle 
These are the parts of a body These are the parts of a cell 
These are found in multicellular organisms These are found in unicellular organisms 
These are macroscopic in nature These are microscopic in nature 
Example: Brain, Heart, Lungs Example: Cytoplasm, mitochondria 
3. Write down the differences between the nucleus and nucleoid.
Answer
Nucleus Nucleoid 
A nucleus is a membrane-bound structure in which 
eukaryotes store their genetic materials. 
Nucleoid is a particular area in which 
prokaryotes store their genetic materials. 
Contains many chromosomes. Contains one chromosomes 
It is a spherically shaped organelle. It is an irregularly shaped organelle. 
Nucleoplasm and Nucleolus are present in the nucleus. Nucleoplasm and Nucleolus are absent in the 
nucleoid. 
4. Mention differences between light microscope and electron microscope. 
Answer 
Light microscope Electron microscope 
Uses light as an illuminating source Uses electrons beam as an illuminating source 
Both live and dead specimen can be seen Only dead and the dried specimen can be seen 
It has low resolution It has high resolution 
5. Give a brief account of the discovery of the cell. 
Answer 
Cells are the basic structural and functional unit of life. The term cells was first coined in 1665 by a 
British scientist Robert Hooke. He was the first person to study living things under a microscope and 
examined a thin slice of cork under a microscope and observed honeycomb-like structures. Robert 
Hooke called these structures as cells. 
  
6. Describe the proteins of the plasma membrane. 
Answer 
There are two types of proteins molecules are found in the plasma membrane: 
(i) Intrinsic proteins -They completely cover the lipid bilayer. 
(ii) Extrinsic proteins – These occur either on the outer surface or on the inner surface of the lipid 
layer. 
7. Enumerate functions of the plasma membrane. 
Answer 
• The plasma membrane forms a barrier between the cell organelles from the outside 
environment. 
• It allows only certain molecules to pass through it. 
• It facilitates communication and signaling between the cells. 
8. Give an example of diffusion across the plasma membrane. 
Answer 
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1. Distinguish between prokaryotic and eukaryotic cells.
Answer 
Prokaryotic Eukaryotic 
Organisms are always unicellular Organisms are always unicellular and multicellular 
Nucleus is absent Nucleus is present 
Cell division takes place through binary fission Cell division takes place through mitosis 
DNA arrangement is circular DNA arrangement is linear 
Example: Bacteria, Blue-green algae Example: Plant and animal cell 
2. Write down the differences between organ and organelle.
Answer
Organ Organelle 
These are the parts of a body These are the parts of a cell 
These are found in multicellular organisms These are found in unicellular organisms 
These are macroscopic in nature These are microscopic in nature 
Example: Brain, Heart, Lungs Example: Cytoplasm, mitochondria 
3. Write down the differences between the nucleus and nucleoid.
Answer
Nucleus Nucleoid 
A nucleus is a membrane-bound structure in which 
eukaryotes store their genetic materials. 
Nucleoid is a particular area in which 
prokaryotes store their genetic materials. 
Contains many chromosomes. Contains one chromosomes 
It is a spherically shaped organelle. It is an irregularly shaped organelle. 
Nucleoplasm and Nucleolus are present in the nucleus. Nucleoplasm and Nucleolus are absent in the 
nucleoid. 
4. Mention differences between light microscope and electron microscope. 
Answer 
Light microscope Electron microscope 
Uses light as an illuminating source Uses electrons beam as an illuminating source 
Both live and dead specimen can be seen Only dead and the dried specimen can be seen 
It has low resolution It has high resolution 
5. Give a brief account of the discovery of the cell. 
Answer 
Cells are the basic structural and functional unit of life. The term cells was first coined in 1665 by a 
British scientist Robert Hooke. He was the first person to study living things under a microscope and 
examined a thin slice of cork under a microscope and observed honeycomb-like structures. Robert 
Hooke called these structures as cells. 
  
6. Describe the proteins of the plasma membrane. 
Answer 
There are two types of proteins molecules are found in the plasma membrane: 
(i) Intrinsic proteins -They completely cover the lipid bilayer. 
(ii) Extrinsic proteins – These occur either on the outer surface or on the inner surface of the lipid 
layer. 
7. Enumerate functions of the plasma membrane. 
Answer 
• The plasma membrane forms a barrier between the cell organelles from the outside 
environment. 
• It allows only certain molecules to pass through it. 
• It facilitates communication and signaling between the cells. 
8. Give an example of diffusion across the plasma membrane. 
Answer 
In unicellular organisms like Amoeba, gaseous exchange takes place through the process of 
diffusion. 
9. Set up an experiment to demonstrate osmosis. 
Answer 
1. Take three raisins and weigh them on the common balance. Let this value be W1. 
2. Keep these raisins in a bowl containing water for 2 hours. 
3. Take the raisins out of the water and gently dry them with the help of blotting paper. 
4. Weigh the soaked swollen raisins again on the common balance. Let this value be W2. 
The soaked swollen raisins (W2) weigh more than the dry raisins (W1). This is because the raisins 
absorbed water by the process of endosmosis. 
10. Write down the differences between diffusion and osmosis. 
Answer 
Diffusion Osmosis 
This occurs in all mediums – Solid, Liquid and gas. This occurs only in the liquid medium. 
Do not require a semipermeable membrane. Requires a semipermeable membrane. 
The flow of particles occurs in all the directions. The flow of particles occurs only in one direction. 
11. Write a note on endocytosis. 
Answer 
Endocytosis is defined as the process of trapping a particle or substance from the external 
environment by engulfing it. Endocytosis is of two types viz phagocytosis, also known as cellular 
eating and pinocytosis, also referred to as cellular drinking. There are three types of endocytosis: 
1. Phagocytosis, 2. Pinocytosis and 3. Receptor-mediated endocytosis. 
12. What would happen when eukaryotic cells are placed in hypotonic, hypertonic and 
isotonic solutions? 
Answer 
When eukaryotic cells are placed in the following solutions the changes observed are as follows: 
• Hypotonic Solution: The water moves from a region of low osmolarity to a region of high 
osmolarity. In this case, since the extracellular fluid has low osmolarity, the water would rush 
into the cell. The cell would then expand and eventually lyse or burst. 
• Hypertonic Solution: In this case, water will leave the cell since the cell has a lower 
osmolarity than the extracellular fluid. As a result the cell would shrink in what is called 
plasmolysis. 
• Isotonic Solution: The osmolarity of both fluids is equal. As such, though water diffuses in 
and out, there is no net change in the volume of the cell. 
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1. Distinguish between prokaryotic and eukaryotic cells.
Answer 
Prokaryotic Eukaryotic 
Organisms are always unicellular Organisms are always unicellular and multicellular 
Nucleus is absent Nucleus is present 
Cell division takes place through binary fission Cell division takes place through mitosis 
DNA arrangement is circular DNA arrangement is linear 
Example: Bacteria, Blue-green algae Example: Plant and animal cell 
2. Write down the differences between organ and organelle.
Answer
Organ Organelle 
These are the parts of a body These are the parts of a cell 
These are found in multicellular organisms These are found in unicellular organisms 
These are macroscopic in nature These are microscopic in nature 
Example: Brain, Heart, Lungs Example: Cytoplasm, mitochondria 
3. Write down the differences between the nucleus and nucleoid.
Answer
Nucleus Nucleoid 
A nucleus is a membrane-bound structure in which 
eukaryotes store their genetic materials. 
Nucleoid is a particular area in which 
prokaryotes store their genetic materials. 
Contains many chromosomes. Contains one chromosomes 
It is a spherically shaped organelle. It is an irregularly shaped organelle. 
Nucleoplasm and Nucleolus are present in the nucleus. Nucleoplasm and Nucleolus are absent in the 
nucleoid. 
4. Mention differences between light microscope and electron microscope. 
Answer 
Light microscope Electron microscope 
Uses light as an illuminating source Uses electrons beam as an illuminating source 
Both live and dead specimen can be seen Only dead and the dried specimen can be seen 
It has low resolution It has high resolution 
5. Give a brief account of the discovery of the cell. 
Answer 
Cells are the basic structural and functional unit of life. The term cells was first coined in 1665 by a 
British scientist Robert Hooke. He was the first person to study living things under a microscope and 
examined a thin slice of cork under a microscope and observed honeycomb-like structures. Robert 
Hooke called these structures as cells. 
  
6. Describe the proteins of the plasma membrane. 
Answer 
There are two types of proteins molecules are found in the plasma membrane: 
(i) Intrinsic proteins -They completely cover the lipid bilayer. 
(ii) Extrinsic proteins – These occur either on the outer surface or on the inner surface of the lipid 
layer. 
7. Enumerate functions of the plasma membrane. 
Answer 
• The plasma membrane forms a barrier between the cell organelles from the outside 
environment. 
• It allows only certain molecules to pass through it. 
• It facilitates communication and signaling between the cells. 
8. Give an example of diffusion across the plasma membrane. 
Answer 
In unicellular organisms like Amoeba, gaseous exchange takes place through the process of 
diffusion. 
9. Set up an experiment to demonstrate osmosis. 
Answer 
1. Take three raisins and weigh them on the common balance. Let this value be W1. 
2. Keep these raisins in a bowl containing water for 2 hours. 
3. Take the raisins out of the water and gently dry them with the help of blotting paper. 
4. Weigh the soaked swollen raisins again on the common balance. Let this value be W2. 
The soaked swollen raisins (W2) weigh more than the dry raisins (W1). This is because the raisins 
absorbed water by the process of endosmosis. 
10. Write down the differences between diffusion and osmosis. 
Answer 
Diffusion Osmosis 
This occurs in all mediums – Solid, Liquid and gas. This occurs only in the liquid medium. 
Do not require a semipermeable membrane. Requires a semipermeable membrane. 
The flow of particles occurs in all the directions. The flow of particles occurs only in one direction. 
11. Write a note on endocytosis. 
Answer 
Endocytosis is defined as the process of trapping a particle or substance from the external 
environment by engulfing it. Endocytosis is of two types viz phagocytosis, also known as cellular 
eating and pinocytosis, also referred to as cellular drinking. There are three types of endocytosis: 
1. Phagocytosis, 2. Pinocytosis and 3. Receptor-mediated endocytosis. 
12. What would happen when eukaryotic cells are placed in hypotonic, hypertonic and 
isotonic solutions? 
Answer 
When eukaryotic cells are placed in the following solutions the changes observed are as follows: 
• Hypotonic Solution: The water moves from a region of low osmolarity to a region of high 
osmolarity. In this case, since the extracellular fluid has low osmolarity, the water would rush 
into the cell. The cell would then expand and eventually lyse or burst. 
• Hypertonic Solution: In this case, water will leave the cell since the cell has a lower 
osmolarity than the extracellular fluid. As a result the cell would shrink in what is called 
plasmolysis. 
• Isotonic Solution: The osmolarity of both fluids is equal. As such, though water diffuses in 
and out, there is no net change in the volume of the cell. 
13. Name the following: 
(a) Smallest cell organelle 
(b) Largest cell organelle; 
(c) ER studded with ribosomes 
(d) Functional segments of the DNA molecule. 
Answer : 
(a) Ribosome 
(b) Plastid in plants and Nucleus in animal cell 
(c) Rough endoplasmic reticulum contains a ribosome attached to its surface 
(d) Genes 
14. Distinguish between the following: 
(a) Chromoplast and chloroplast 
(b) Ribosome and centrosome 
Answer 
(a) 
Chromoplast Chloroplast 
Chromoplasts are plastids and contain carotenoids Chromoplasts– is a name given to an area for all 
the pigments to be kept and synthesized in the 
plant. 
They lack in chlorophyll They have a high concentration of chlorophyll 
Chromoplasts may develop from green chloroplasts. 
Chlorophyll and thylakoid membranes disappear and 
carotenoids are accumulated, e.g. during ripening of 
fruits 
Chloroplast has a structure called chlorophyll 
which functions by trapping the solar energy and 
used for the synthesis of food in all green plants. 
(b) 
Ribosome Centrosome 
Helps in protein synthesis Plays major role in cell division 
Found in both plants and animals Found in only plants 
Ribosomes are scattered everywhere inside the cell Centrosome found inside nucleus only 
15. Write the main differences between plant and animal cells. 
Answer 
Plant cell Animal cell 
Page 5


 
1. Distinguish between prokaryotic and eukaryotic cells.
Answer 
Prokaryotic Eukaryotic 
Organisms are always unicellular Organisms are always unicellular and multicellular 
Nucleus is absent Nucleus is present 
Cell division takes place through binary fission Cell division takes place through mitosis 
DNA arrangement is circular DNA arrangement is linear 
Example: Bacteria, Blue-green algae Example: Plant and animal cell 
2. Write down the differences between organ and organelle.
Answer
Organ Organelle 
These are the parts of a body These are the parts of a cell 
These are found in multicellular organisms These are found in unicellular organisms 
These are macroscopic in nature These are microscopic in nature 
Example: Brain, Heart, Lungs Example: Cytoplasm, mitochondria 
3. Write down the differences between the nucleus and nucleoid.
Answer
Nucleus Nucleoid 
A nucleus is a membrane-bound structure in which 
eukaryotes store their genetic materials. 
Nucleoid is a particular area in which 
prokaryotes store their genetic materials. 
Contains many chromosomes. Contains one chromosomes 
It is a spherically shaped organelle. It is an irregularly shaped organelle. 
Nucleoplasm and Nucleolus are present in the nucleus. Nucleoplasm and Nucleolus are absent in the 
nucleoid. 
4. Mention differences between light microscope and electron microscope. 
Answer 
Light microscope Electron microscope 
Uses light as an illuminating source Uses electrons beam as an illuminating source 
Both live and dead specimen can be seen Only dead and the dried specimen can be seen 
It has low resolution It has high resolution 
5. Give a brief account of the discovery of the cell. 
Answer 
Cells are the basic structural and functional unit of life. The term cells was first coined in 1665 by a 
British scientist Robert Hooke. He was the first person to study living things under a microscope and 
examined a thin slice of cork under a microscope and observed honeycomb-like structures. Robert 
Hooke called these structures as cells. 
  
6. Describe the proteins of the plasma membrane. 
Answer 
There are two types of proteins molecules are found in the plasma membrane: 
(i) Intrinsic proteins -They completely cover the lipid bilayer. 
(ii) Extrinsic proteins – These occur either on the outer surface or on the inner surface of the lipid 
layer. 
7. Enumerate functions of the plasma membrane. 
Answer 
• The plasma membrane forms a barrier between the cell organelles from the outside 
environment. 
• It allows only certain molecules to pass through it. 
• It facilitates communication and signaling between the cells. 
8. Give an example of diffusion across the plasma membrane. 
Answer 
In unicellular organisms like Amoeba, gaseous exchange takes place through the process of 
diffusion. 
9. Set up an experiment to demonstrate osmosis. 
Answer 
1. Take three raisins and weigh them on the common balance. Let this value be W1. 
2. Keep these raisins in a bowl containing water for 2 hours. 
3. Take the raisins out of the water and gently dry them with the help of blotting paper. 
4. Weigh the soaked swollen raisins again on the common balance. Let this value be W2. 
The soaked swollen raisins (W2) weigh more than the dry raisins (W1). This is because the raisins 
absorbed water by the process of endosmosis. 
10. Write down the differences between diffusion and osmosis. 
Answer 
Diffusion Osmosis 
This occurs in all mediums – Solid, Liquid and gas. This occurs only in the liquid medium. 
Do not require a semipermeable membrane. Requires a semipermeable membrane. 
The flow of particles occurs in all the directions. The flow of particles occurs only in one direction. 
11. Write a note on endocytosis. 
Answer 
Endocytosis is defined as the process of trapping a particle or substance from the external 
environment by engulfing it. Endocytosis is of two types viz phagocytosis, also known as cellular 
eating and pinocytosis, also referred to as cellular drinking. There are three types of endocytosis: 
1. Phagocytosis, 2. Pinocytosis and 3. Receptor-mediated endocytosis. 
12. What would happen when eukaryotic cells are placed in hypotonic, hypertonic and 
isotonic solutions? 
Answer 
When eukaryotic cells are placed in the following solutions the changes observed are as follows: 
• Hypotonic Solution: The water moves from a region of low osmolarity to a region of high 
osmolarity. In this case, since the extracellular fluid has low osmolarity, the water would rush 
into the cell. The cell would then expand and eventually lyse or burst. 
• Hypertonic Solution: In this case, water will leave the cell since the cell has a lower 
osmolarity than the extracellular fluid. As a result the cell would shrink in what is called 
plasmolysis. 
• Isotonic Solution: The osmolarity of both fluids is equal. As such, though water diffuses in 
and out, there is no net change in the volume of the cell. 
13. Name the following: 
(a) Smallest cell organelle 
(b) Largest cell organelle; 
(c) ER studded with ribosomes 
(d) Functional segments of the DNA molecule. 
Answer : 
(a) Ribosome 
(b) Plastid in plants and Nucleus in animal cell 
(c) Rough endoplasmic reticulum contains a ribosome attached to its surface 
(d) Genes 
14. Distinguish between the following: 
(a) Chromoplast and chloroplast 
(b) Ribosome and centrosome 
Answer 
(a) 
Chromoplast Chloroplast 
Chromoplasts are plastids and contain carotenoids Chromoplasts– is a name given to an area for all 
the pigments to be kept and synthesized in the 
plant. 
They lack in chlorophyll They have a high concentration of chlorophyll 
Chromoplasts may develop from green chloroplasts. 
Chlorophyll and thylakoid membranes disappear and 
carotenoids are accumulated, e.g. during ripening of 
fruits 
Chloroplast has a structure called chlorophyll 
which functions by trapping the solar energy and 
used for the synthesis of food in all green plants. 
(b) 
Ribosome Centrosome 
Helps in protein synthesis Plays major role in cell division 
Found in both plants and animals Found in only plants 
Ribosomes are scattered everywhere inside the cell Centrosome found inside nucleus only 
15. Write the main differences between plant and animal cells. 
Answer 
Plant cell Animal cell 
Cell wall is present Cell wall is absent 
Nucleus lies on one side of the cell Nucleus lies on one center of the cell 
16. What will happen in a cell if its nucleus is removed? Give reasons in support of your 
answer. 
Answer 
If the nucleus of a cell is removed the cell will not be able to carry out its vital functions and will die. 
17. Explain why do spinach looks green, papaya yellow and edible part of watermelon red? 
Answer 
Spinach is green because of the presence of green pigment chlorophyll. Papaya is yellow because 
of the presence of caricaxanthin. The edible part of a watermelon is red in color because of the 
presence of lycopene which is a red pigment. 
18. Write down two main functions of 
(a) Endoplasmic reticulum 
(b) Lysosome 
Answer 
(a) Endoplasmic reticulum 
• It plays a major role in the production, processing, and transport of proteins and lipids. 
• It produces transmembrane proteins and lipids for its membrane and for many other cell 
components including lysosomes, secretory vesicles, the Golgi apparatus, the cell 
membrane, and plant cell vacuoles. 
(b) Lysosomes 
• Intracellular digestion 
• Removal of dead cells 
19. Name the following 
(a) The cell organelle which synthesizes protein. 
(b) The type of plastid which stores food. 
Answer: 
(a) Ribosome 
(b) Leucoplasts 
20. Lysosomes are known as suicide bags.” Why? 
Answer: 
Lysosomes are known as suicide bags of the cell because they contain lytic enzymes capable of 
digesting cells and unwanted materials. When lysosomes burst, the lytic enzymes within the 
organelle spill all over the cell, rupturing the cell membrane or cell wall, inducing the death of the 
cell.