Class IX Solution of THE FUNDAMENTAL UNIT OF LIFE

I Very short answer type questions:

1. What are living organisms made up of?
   Ans. Living things are made up of basic unit cells.
2. Cells were first discovered by whom?
   Ans. The cell was first discovered by Robert Hooke.
3. What are the unicellular and multicellular organisms?
   Ans. Single-celled organisms like amoeba, Chlamydomonas, paramecium, and bacteria are called unicellular organisms. On the other hand, if the organism is made up of more than one cell like fungi, plants, and animals are called multicellular organisms.
4. Who coined the term ‘protoplasm’ for the fluid substance of the cell?
   Ans. Purkinje in 1839 coined the term ‘protoplasm’ for the fluid substance of the cell.
5. Who discovered the nucleus in the cell?
   Ans. Robert Brown.
6. Write the name of three features that are present in almost every cell and all activities inside the cell and interactions of the cell with its environment are possible due to these features.
   Ans. Cell walls, nucleus, and cytoplasm.
7. What is cell theory?
   Ans. Every organism made up of one or many cells, the structural and functional unit of life is cell and all cells arise from preexisting cells.
8. Which organelle have their own DNA and ribosomes so they are able to make some of their own proteins.
   Ans. Mitochondria.
9. Write the name of three unicellular organisms.
   Ans. Chlamydomonas, paramecium and bacteria.
10. Define osmosis.
    Ans. The movement of water molecules from higher concentration to lower concentration of water through a selectively permeable membrane is called osmosis.
11. Define diffusion.
    Ans. Movement of anything from a region of high concentration to a region of low concentration is called diffusion.
12. What is the full form of DNA?
    Ans. Deoxyribose nucleic acid.
13. What is the full form of RNA?
    Ans. Ribonucleic acid.
14. What is a gene?
    Ans. Gene is a heredity factor and made up of DNA. Genes act as instructions to make molecules of proteins in the cell.
15. State the function of chromosomes in a cell.
    Ans. The chromosomes are the actual heredity factor present in the nucleus of the cell that regulates the function by which a cell can divide or reproduce of its own kind.
16. What are cell organelles?
    Ans. Cell organelles are the structures present in the cytoplasm of the cell and they are the most important part of the cell and concerned with specific functions.
17. What are cellulose and its function?
    Ans. Cellulose is a complex substance present in the cell wall of the plants, which is rigid and provides structural strength and shapes to the cell of the plants.
18. Why is it said that "a cell without a nucleus is without any feature"?
    Ans. It is said that a cell without a nucleus is without any future because the nucleus is the most important part of the cell which controls and coordinates all the functions and life processes of a cell. It plays an important role in cellular reproduction in which a cell divides to form new daughter cells.
19. What do you mean by nucleoid?
    Ans. An undefined nuclear region in the cell-like bacteria containing only nucleic acids is called a nucleoid.
20. Write the function of Chromatin material.
    Ans. The nucleus in its nucleoplasm contains a thread-like structure called chromatin material. During cell division, the chromatin material becomes thick and gets organized into chromosomes.
21. What role does a nucleus play in cellular reproduction?
    Ans. The nucleus plays an important role in cellular reproduction. It carries the hereditary information and it divides to form two new cells by the process of cellular reproduction. 
22. What is the function of DNA?
    Ans. It stores long tome all of the genetic information for making proteins for the development and function of living things.
23. What is cellulose?
    Ans. Cellulose is a complex substance present in the cell wall of the plants, which is rigid and provides structural strength and shapes to the cell of the plants.
24. What is the plasma membrane?
    Ans. The plasma membrane is very thin, flexible and surrounds the cell that separates the contents of the cell from its external environment. It consists of small pores that allow the entry and exit of certain materials in and out of the cell.
25. What is the plasma membrane made up of?
    Ans. Plasma membrane made up of a very thin, delicate and flexible membrane that contains small pores.

II Short answer type questions:

1. Why the cell membrane is called a selectively permeable membrane.
   Ans. The cell membrane allows the entry and exit of some materials in and out of the cell and prevents movement of some other materials. Due to this function, it is called a selectively permeable membrane.
2. What will happen if we put an animal cell or a plant cell into a solution of sugar or salt in water?
   Ans. Osmosis is the movement of water molecules from high to low concentration. If we put an animal cell or a plant cell into a solution of sugar or salt in water, as sugar or salt solution is a hypertonic solution (lower concentration of water) cell will lose water by outward osmosis and it will shrink.
3. What is the role of SER?
   Ans. The SER smooth endoplasmic reticulum helps in the manufacture of fat molecules or lipids, that are important for cell function. Some of these proteins and lipids help in building the cell membrane.
4. What do you mean by endocytosis? Write the name of an organism that acquires its food through such processes.
   Ans. Endocytosis is a cellular process in which the cell membrane enables the cell to engulf in food or other substances from its outside environment. Such processes are known as endocytosis. Amoeba acquires its food through such processes.
5. What is stroma?
   Ans. The internal organization of the plastids consists of numerous membrane layers embedded in a material called the stroma.
6. Which organelles of the plant cell are similar to mitochondria?
   Ans. Plastids are similar to mitochondria.
   Mitochondria and plastids both have their own DNA and ribosomes. Mitochondria capture energy in cellular respiration and chloroplast of plastid capture energy in photosynthesis.
7. What do you mean by plasmolysis?
   Ans. Plasmolysis is a phenomenon in which a living plant cell loses water through osmosis and there is shrinkage of the cell away from the cell wall.
8. How are vacuoles in plant cells different from those in animal cells?
   Ans. In-plant cells, vacuoles are very large and in animal cells, vacuoles are very small sized.
9. What is a centrosome and what function does it perform?
   Ans. A centrosome is cell organelles found only in the animal cell which regulate and initiate the cell division.
10. Describe in short the chief component of a nucleus.
    Ans. The chief component of a nucleus is the nucleolus, chromatin, chromosomes, nucleoplasm, and nuclear membrane.
11. Why mitochondria are also referred to as strange organelles?
    Ans. Mitochondria are referred to as strange organelles because they have their own DNA to prepare and ribosomes to prepare proteins. 
12. Distinguish between the cell wall and cell membrane.
    Ans.                            
                   
    

    Cell Wall	Cell Membrane
    1. It is a nonliving structure	It is a living structure
    2. It is made up of cellulose	It is made up of protein and lipids.
    3. It is present only in the plant cells.	It is present in all cells.

13. What is the cell wall? What is a cell wall made up of?
    Ans. A rigid outer covering of plant cells is called a cell wall. It lies outside the plasma membrane. Cell walls made up of complex substance cellulose.
14. Write the main functions of the cell wall.
    Ans. The cell wall protects the plant cell from the entry of disease-causing agents as well as the underlying protoplasm against mechanical injuries.
15. Give any two functions of plastids.
    Ans. Two functions of plastids are:
    Plastid as a chloroplast contains green pigment chlorophyll that captures light energy and helps in photosynthesis.
    Plastid as a leucoplast stores starch, oils, and protein granules.
16. Give any two functions of the plasma membrane.
    Ans. The plasma membrane is the outermost covering of the cell.
    It separates the contents of the cell from its external environment.
    The plasma membrane allows the entry and exit of some materials in and out of the cell and prevents movement of some other materials.
17. Name two nucleic acids present in the cell and their function.
    Ans. Two nucleic acids are DNA (Deoxyribonucleic acid) and RNA (Ribonucleic acid).
    DNA - Chromosomes are composed of DNA and protein. DNA molecules contain the information necessary for constructing and organizing cells and functional segments of DNA are called genes.
    RNA – It helps in protein synthesis.
18. Write two similarities and one of the dissimilarities between mitochondria and plastid.
    Ans. Two similarities:. Plastids are similar to mitochondria.
    Mitochondria and plastids both have their own DNA and ribosomes.
    Mitochondria capture energy in cellular respiration and chloroplast of plastid capture energy in photosynthesis.
    One dissimilarity:
    Plastids are present only in plants and green organisms whereas mitochondria present in all cells.
19. Division of labor exists even at the intracellular level. Justify the statement.
    Ans. Each cell has got certain specific components called cell organelles. Each kind of cell organelle performs a special function, and the cell is able to live and perform all its functions because of these organelles. These organelles together constitute the basic unit of the cell. Therefore a division of labor exists even at the intracellular level.
20. Define osmosis. In what two ways it is different from diffusion?
    Ans. Osmosis - The movement of water molecules from higher concentration to lower concentration of water through a selectively permeable membrane is called osmosis.
    Osmosis occurs only in liquid medium whereas diffusion can occur in any medium.
    In osmosis, only the solvent molecules cross the membrane whereas in diffusion solvent and solute particles are free to move.
21. Draw and label the parts of the prokaryotic cells.                                Ans.
22. Name three types of plastids found in plant cells and give one function of each.Ans. Three types of plastids are chloroplast, chromoplast, and leucoplast.
    Functions are:
    Chromoplast – Provides colour to the leaf fruits and flowers.
    Chloroplast- Contain green pigments and helps in photosynthesis.
    Leucoplast – Helps in-store starch, oils and protein granules prepared by plants.
23. What is the name given to the thread shaped structures in the nucleus? Why is it important?
    Ans. The thread shaped structures in the nucleus are known as chromosomes.
    Important- The chromosomes are the actual heredity factor present in the nucleus of the cell that regulates the function by which a cell can divide or reproduce of its own kind.
24. How does the movement of substances take place into the cell?
    Ans. Some substances like carbon dioxide or oxygen can move across the cell membrane by a process called diffusion. Example – O₂ enters the cell by the process of diffusion when the level or concentration of O₂ inside the cell decreases. Similarly, CO₂ accumulates in high concentrations inside the cell. So CO₂ moves out of the cell, from a region of high concentration to a region of low concentration outside the cell by the process of diffusion.
25. Name:
    (a) The main constituent substance present in the plant cell wall.
    (b) A cell organelle which lacks membrane.
    (c) Two nucleic acids present in the cell. 
    Ans. (a) Cellulose is the main constituent substance present in the plant cell wall.
    (b) In prokaryotes, the nucleus has no membrane.
    (c) DNA and RNA

III. Long answer type questions:

1. What is the endoplasmic reticulum? Name the two types of the endoplasmic reticulum. Write its main function.
   Ans. The endoplasmic reticulum ER is a large network of membrane-bound long tubes and sheets. There are two types of ER– rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER).
   RER has particles called ribosomes attached to its surface and SER has no ribosomes.
   Function: RER helps in the manufacture of protein.
   SER helps in the manufacture of fat molecules, or lipids, important for cell function and also helps in building the cell membrane.
2. (a) List any two structural differences and two similarities between a plant cell and an animal cell.
   (b) What would happen if an animal cell is kept in distilled water for 24 hours?
   Ans. (a)  I. Differences between plant cell and animal cell:
   Plant cells have cell walls whereas the animal cell does not have cell walls.
   Plant cells have plastids whereas animal cells do not have plastids.
   II. Similarities between plant cell and animal cells:
   Both cells contain mitochondria, ribosomes, endoplasmic reticulum, and nucleus.
   Bothe are eukaryotic cells that contain a nucleus and organelles and are enclosed by a plasma membrane.
   (b) Distilled water has a higher water concentration than the cell. Therefore the outside solution is very dilute and such a solution is known as a hypotonic solution, so when an animal cell is kept in distilled water for 24 hours the cell will gain water by osmosis. The cell is likely to swell up.
3. Write the structure and functions of the ER.
   Ans. Endoplasmic reticulum ER forms a network system. It has a large network of membrane-bound long tubules or round vesicles. There are two types of ER– RER (rough endoplasmic reticulum) and SER (smooth endoplasmic reticulum). RER is rough because it has particles attached to its surface called ribosomes attached to its surface. The ribosomes are the sites of protein manufacture and these manufactured proteins are sent to various places in the cell depending on need, using the ER. SER does not have ribosomes, it helps in the manufacture of fat molecules, or lipids that help in cell function and some of these proteins help in building the cell membrane.
4. Write the differences between hypotonic and isotonic solutions.
   Ans. Differences between hypotonic and isotonic solution:
   Hypotonic solution - If the solution has a higher water concentration than the other, or solution is very dilute than the other and has a lower osmotic pressure, then the solution is known as a hypotonic solution.
   Isotonic solution - - If the solutions have exact same water concentration and same osmotic pressure across a semipermeable membrane the solution is known as an isotonic solution. In isotonic solutions, water crosses the semipermeable membrane in both directions and there is no overall movement of water.
5. (a) Write two points of difference between the nuclear region of a bacterial cell and a region of an animal cell.
   (b) Which structure present in the nucleus of a living cell bear genes?
   Ans. (a) Difference between the nuclear region of a bacterial cell and a region of an animal cell:
   The nuclear region of the cell of bacteria poorly defined due to the absence of a nuclear membrane and this region contains only nucleic acids is called a nucleoid. These cells are cells prokaryotic cells.
   Animal cells have a nuclear membrane and are called eukaryotes. The nuclear membrane has pores which allow the transfer of material from inside the nucleus to its outside to the cytoplasm
   (b) Chromosomes present in the nucleus of a living cell bear genes that contain information for the inheritance of features from parents to the next generation in the form of DNA and functional segments of DNA are genes.
6. Draw a diagram of a plant cell and label it's any for parts. Mention any three features of prokaryotic cells.
   Ans. 
   
   
                                                                 Plant Cell
   Three feature of prokaryotic cells:
   (i) Prokaryotic cells have a lack of nuclear membrane,
   (ii) Prokaryotic cells lack most of the cytoplasmic organelles.
   (iii) Cell division takes place by budding or fission.
7. Write the differences between prokaryotic and eukaryotic cells.
   Ans. Differences between prokaryotic and eukaryotic cells:
   Prokaryotes cells lack a nuclear membrane whereas eukaryotic cells have a nuclear membrane.
   Prokaryotic cells also lack most of the other cytoplasmic organelles ( Golgi apparatus, mitochondria, ER) while present in eukaryotic cells.
   Prokaryotic cells do not contain membrane-bound organelles while eukaryotic cells contain.
   Prokaryotic cells are usually unicellular whereas eukaryotic cells are multicellular.
   The chloroplast is absent in prokaryotic but chlorophyll scattered in the cytoplasm whereas chloroplast present in the eukaryotic (plant).
8. Differentiate between rough and smooth endoplasmic reticulum. How is the endoplasmic reticulum important for membrane biogenesis?
   Ans. Differentiate between rough and smooth endoplasmic reticulum:
   Rough endoplasmic reticulum –
   RER is rough in texture because it has particles called ribosomes attached to its surface. The ribosomes are the sites of protein manufacture.
   Smooth endoplasmic reticulum –
   SER does not contain ribosomes and is smooth. SER helps in the manufacture of fat molecules or lipids which are important for cell function.
   Protein synthesized by RER and lipid synthesized by SER is helpful in the building of cell membranes that is the process is membrane biogenesis.
9. Write one function each of ribosomes, vacuole, and plasma membrane.
   Ans. Functions of :
   Ribosomes – Ribosomes are the site of protein synthesis.
   Vacuoles - Vacuoles are storage sacs for solid or liquid contents like amino acids, sugars, various organic acids, and some proteins. In-plant cells, vacuoles provide turgidity and rigidity to the cell.
   Plasma membrane – It is the outermost covering of the cell and separates the contents of the cell from its external environment. It allows the entry and exit of some materials in and out of the cell and prevents the movement of some other unwanted materials.
10. Describe the role played by the lysosomes in a Cell. Why these are termed as suicidal bags? How do they perform their function?Ans. Lysosomes are the waste disposal system of the cell and help to keep the cell clean by digesting any foreign material such as bacteria or food, worn-out cell organelles, and old organelles. Lysosomes contain powerful digestive enzymes that are capable of breaking down all organic material and destroying the cell. So the lysosomes are known as the ‘suicide bags’ of a cell. When the cell gets damaged, lysosomes may burst and the enzymes can digest their own cell.
11. Distinguish leucoplast from chromoplast based on one feature. Give an example of chromoplast present in plant cells. What is the function of the chromoplast in the plant cell?
    Ans. Differences between leucoplast and chromoplast:
    Leucoplast is colourless plastids and helps to store starch, oil, and protein granules.
    Chromoplast is a colour plastid and helps to give colour to the leaves and fruits of the plant.
    For example, due to carotenoid pigment lycopene that makes a ripe tomato green to red.
    Function: Chromoplast gives colour to the flower and fruits. The bright colour of flowers helps in pollination by attracting insects.
12. Who gave the term Golgi apparatus? Name one cell organelles that are formed by the Golgi apparatus. Write any two functions of the Golgi apparatus.
    Ans. Camillo Golgi gave the term Golgi apparatus.
    Lysosomes in the cell organelles are formed by the Golgi apparatus.
    Functions of Golgi apparatus- (i) Protein synthesized by RER and lipids synthesized by SER are travels outside the cell through the Golgi apparatus.
    (ii) It helps in the creation of lysosomes which is the waste disposal system of the cell and helps in the storage, modification, and packaging of products in vesicles for secretion. 
13. Endocytosis is found only in animals. State and explain the process by which an amoeba obtains its food.
    Ans. The plasma membrane of an animal cell of amoeba is flexible. It is made up of organic molecules called lipids and proteins. The flexibility of the cell membrane enables the cell to engulf in food particles and other material from its external environment with the help of pseudopodia. After engulfing the food particles by the process of endocytosis, amoeba forms a vacuole around it. When the particle has completely trapped the cell of amoeba secretes digestive enzymes that digest the food. After digestion waste material excretes by the process of exocytosis.  
14. A cell is the fundamental structural unit of living organisms. It is also the basic functional unit of life. Explain it.
    Ans. In all living things such as human, each living cell has the capacity to perform certain basic functions. There is a division of labour in multicellular organisms like human beings. Different parts of the human body perform different functions. Heart in the human body is to pump blood to the different body parts, a stomach to digest food, a kidney to filter blood and so on. These organs are made up of cells. Each cell has a different kind of cell organelles. Each kind of cell organelle performs a special function. A cell is able to live and perform all its functions because of these organelles. These organelles together constitute the basic unit called the cell. Cell together constitute organs and they together constitute an organism. So we can say a cell is the fundamental structural and functional unit of life.
15. Write the functions of the following organelles in a cell:
    chloroplast (ii) nucleus (iii) ribosomes.
    Ans. Functions of the following organelles in a cell are:
    (i) Chloroplast - Plastids contain green pigments called chlorophyll and these are known as chloroplasts. Chloroplasts help in photosynthesis in the plants by trapping solar energy.
    (ii) Nucleus - The nucleus in eukaryotes directs the life processes of the cell. It plays a central role in cellular reproduction. It also plays a crucial part, along with the environment, in determining the way the cell will develop and what form it will exhibit at maturity, by directing the chemical activities of the cell.
    (iii) Ribosomes- The ribosomes are present in all active cells. Ribosomes are the sites of protein manufacture and the manufactured proteins are sent to various places in the cell through the ER endoplasmic reticulum. 
16. Two beakers A & B contain plain water and concentrated sugar solution respectively, an equal number of dry raisins are kept in them for a few hours and then taken out. Explain the reason for the difference in the physical appearance of raisins which were taken out of the two beakers on the basis of the above observation category is that two solutions as hypotonic and hypertonic.
    Ans. Two beakers A & B contain plane water and concentrated sugar solution respectively, an equal number of dry raisins are kept in them for a few hours and then taken out. We will observe the following:
    When we put dried raisins in-plane water of beaker A for a few hours and taken out we will observe that dry raisins gain water and swell. This is because the outside solution is very dilute, the dry raisins will gain water by osmosis. Such a solution is known as a hypotonic solution. 
    However, when placed in the concentrated solution it loses water and consequently shrinks. This is because the medium has a lower concentration of water than the dried raisins, and the raisins will lose water by osmosis. Such a solution is known as a hypertonic solution.
17. Which cell organelles would you associate with ATP Productions? How is this organization to make its own protein?
    Ans. Mitochondria are associated with ATP production. ATP is known as the energy currency of the cell. The energy required for various chemical activities needed for life is released by mitochondria in the form of ATP molecules and so mitochondria are known as the powerhouses of the cell. The body uses energy stored in ATP for making new chemical compounds and for mechanical work.
    Mitochondria are the strange organelles that they have their own DNA and ribosomes due to these mitochondria are able to make some of their own proteins.
18. A student performed an experiment by placing the de-shelled egg in a concentrated salt solution for 5 minutes. What changes did he observe in the egg? Give the reason for the same.
    (a) Why the cell is called the structural and functional unit of life?
    (b) Why the plasma membrane is called a selectively permeable membrane?
    (c) Name the factors which decide the movement of water across the plasma membrane.
    Ans. If we place a  de-shelled egg in a concentrated salt solution for 5 minutes then we will observe the egg will shrink due to water passes out of the egg solution into the salt solution because of the salt the solution is more concentrated.
    (a) Different organs of the human body perform different functions. These organs are made up of cells. Each cell has a different kind of cell organelles. Each kind of cell organelle performs a special function. A cell is able to live and perform all its functions because of these organelles. These organelles together constitute the basic unit called the cell. Cell together constitute organs and they together constitute an organism. So we can say a cell is the fundamental structural and functional unit of life.
    (c) Osmosis is the factor that decides the movement of water across the plasma membrane.
19. State reasons for the following: 
    (a) Mentioned the use of deep folding in the inner membrane of mitochondria. 
    (b) Plastids are able to make their own protein. 
    (c) Plant cells shrink when kept in a hypertonic solution.
    Ans. (a) Mitochondria have two membranes. The outer membrane and inner membrane. The inner membrane is deeply folded. The use of deep folding in the inner membrane of mitochondria is to create a large surface area for ATP-generating chemical reactions.
    (b) Like mitochondria, Plastids have their own DNA and ribosomes due to this they are able to make their own protein.
    (c)The medium of the hypertonic solution has a lower concentration of water than the cell, therefore the cell will lose water by osmosis is a special case of diffusion through a selectively permeable membrane and consequently shrinks.
20. What is membrane biogenesis? Explain what happens when a drop concentrated sugar solution is placed on rheo leaf peel mounted on a glass slide. Name this phenone. Would the same happen if the rheo leaf was boiled before mounting? Give a reason for your answer.
    Ans. RER is rough because it has particles called ribosomes attached to its surface. The ribosomes are the sites of protein manufacture. The manufactured proteins are sent to various places in the cell using the ER. The SER helps in the manufacture of fat molecules, or lipids, important for cell function. Some of these proteins and lipids help in building the cell membrane. This process is known as membrane biogenesis.
    The concentrated sugar solution is called a hypertonic solution. If a cell is placed in a hypertonic solution the water will move out of the cell and the protoplasm will shrink. It is called plasmolysis.
    If the rheo leaves kept in boiled water, the plant cell would be killed and if we put concentrated sugar solution on it nothing happens because the cell is dead and no plasmolysis will take place.
21. What would happen if the plasma membrane rupture or breaks down? What would happen to the life of a cell if there were no Golgi apparatus?
    Ans. The cell membrane is the outermost covering of the cell. The plasma membrane allows the entry and exit of some materials in and out of the cell. It also prevents the movement of some other materials. If the plasma membrane ruptures or breakdown then the cell will not be able to exchange material from its surroundings by diffusion or osmosis. Due to this, the protoplasmic material will be disappeared and the cell will die. 
    The Golgi apparatus helps to package, modification, storage and dispatching the material, synthesized near the ER to various targets inside and outside the cell. Golgi apparatus also make complex sugar from simple sugar. If there is no Golgi apparatus then the packaging and transporting of materials synthesized by cell will not happen.
22. Describe the structure of the plant cell.
    Ans. Plant cells are eukaryotic cells. It has a cell wall, a large vacuole, less number of mitochondria and plastids. There are three types of plastids, chloroplasts, chromoplast, and leucoplast. The cell wall is a rigid layer that is found outside the cell membrane and providing structural support and protection. The cell wall is the non-living protective layer of the plant cells, bacteria, fungi, and algae. The chloroplasts contain a green pigment chlorophyll helps in photosynthesis, chromoplast provides colour to the flower, fruits, and roots and leucoplast helps to store starch, oils, and protein granules.
23. Write the position, function, and structure of different cell organelles.
    Ans. Some important cell organelles are the nucleus, endoplasmic reticulum, Golgi apparatus, lysosomes, mitochondria, plastids, and vacuoles.

24. Cell organelle	Structure	Position	Function
    1. Nucleus	It is a darkly coloured, spherical or oval, dot-like structure has a porous double-layered covering called nuclear membrane.	It is present near the center of each cell.	The nucleus plays an important role in cellular reproduction, growth, protein synthesis, stores the cells hereditary material DNA.
    2. Endoplasmic  Reticulum	The endoplasmic reticulum is a large network of membrane-bound tubes and sheets. There are two types of ER, SER and RER.bRER is a rough ER due to the presence of ribosomes particles.	Endoplasmic reticulum present in the cell near the nucleus and the Golgi apparatus.	SER helps in the manufacture of fat molecules or lipids and RER helps in the manufacture of proteins.
    3. Golgi apparatus	Golgi apparatus consists of a system of membrane-bound vesicles arranged  parallel to each other in stacks called cisterns.	Golgi apparatus present in the cell near the nucleus.	Protein synthesized by RER and lipids synthesized by SER travels outside the cell through the Golgi apparatus. It helps in the creation of lysosomes, helps in the storage, modification, and packaging of products in vesicles for secretion.
    4. Lysosomes	Lysosomes are spherical in shape enclosed by a single membrane.	Lysosomes are present in the cytoplasm of the cell.	Lysosomes help to keep the cell clean by digesting any foreign material like bacteria as well as worn-out cell organelles, old organelles.
    5. Mitochondria	Mitochondria have two membrane coverings instead of just one. The outer membrane is very porous while the inner membrane is deeply folded.	Mitochondria is present in the cytoplasm of the cell.	Mitochondria are the powerhouses of the cell. The energy required for various chemical activities needed for life is released by mitochondria in the form of ATP.
    6. Plastid	They are the double-membrane organelles of the plant cell. There are three types of plastids, chloroplast, chromoplast, and leucoplast.	They are present in the plant cells.	It helps in photosynthesis, provides colour to the fruits and leaves and helps in-store starch, oils, and protein granules.
    7. Vacuoles	They are membrane-bound storage sacs. It is large in size in plant cells and small in the animal cells.	They are present within the cytoplasm of a cell.	It helps in storage, waste disposal, and protection.

25. Draw a diagram of the nucleus to show the given parts:
    (a) Nucleolus (b) Nuclear pore (c) Nuclear envelope. Explain the term (i) endocytosis (ii) plasmolysis.
    Ans. Diagram of the nucleus:
    
    
    (i) Endocytosis - The flexibility of the cell membrane helps to enable the cell to engulf in food and other material from its external environment. These processes are known as endocytosis. Amoeba takes its food through these processes.
    (ii) When a living plant cell loses water through the osmosis process, there is a contraction of the contents of the cell away from the cell wall. This phenomenon is known as plasmolysis.
26. (a) What will happen if the organization of a cell is damaged due to certain physical or chemical reasons?
    (b) How do substances like CO₂ and water move in and out of the cell?
    Ans. (a) Lysosomes are a kind of waste disposal system of the cell that helps to keep the cell clean by digesting any foreign material as well as worn-out cell organelles. Lysosomes are able to do this because they contain powerful digestive enzymes capable of breaking down all organic material. If the organization of a cell is damaged due to certain physical or chemical reasons lysosomes may burst and the enzymes digest their own cell.
    (b) The substances like CO₂ and water move in and out of a cell by the process of diffusion in which substances move from the region of high concentration to low concentration. When the concentration of CO₂ and water is lower in the internal environment than that outside the cell, CO₂ 
    and water move outside the cell and When the concentration of CO₂ and 
    water is higher in the external environment than that inside the cell, CO₂ 
    and water moves inside the cell.
27. Mention the difference between prokaryotes and eukaryotes in terms of nuclear reason present in them. 
    Ans. Prokaryotic – (i) Cells are generally are small,
    (ii) Found in bacteria and blue-green algae,
    (iii) Well defined cell organelles are absent in the cytoplasm,
    (iv) No definite nucleus is present.
    Eukaryotic-
    (i) Cells are generally are large,
    (ii) Found in all other living organisms,
    (iii) Well defined cell organelles are absent in the cytoplasm,
    (iv) The definite nucleus is present.
28. Name:
    (a) The process through which amoeba acquires its food from the external environment.
    (b) Name cell organelles that are termed as suicidal bags of the cell and have membrane-bound sac filled with powerful digestive enzymes.
    (c) Two cell organelles that contain their own genetic material.
    (d) Site of energy release inside the cell.
    Ans. (a) Endocytosis is the process through which amoeba acquires its food from the external environment by using its pseudopodia.
    (b) Lysosomes are termed as suicidal bags of the cell and have membrane-bound sac filled with powerful digestive enzymes.
    (c) Mitochondria and chloroplasts contain their own genetic material.
    (d) Mitochondria is the site of energy that stores energy in the form of ATP and releases inside the cell.
29. Name:
    The kind of plastid is important for photosynthesis in the leaves of the plants.
    The cell organelle that detoxifies poisons and drugs into the liver of vertebrates. 
    Two cell organelles having a double-membrane envelope.
    Two materials stored in leucoplasts.
    Ans. (a) The chloroplast of plastid contains green pigment that is important for photosynthesis in the leaves of the plants.
    (b) Endoplasmic reticulum detoxifies poisons and drugs into the liver of vertebrates.
    (c) Mitochondria and endoplasmic reticulum having a double-membrane envelope.
    (d) Starch and oil are stored in leucoplasts.
30. Name:
    (a) The organelles are associated with protein synthesis.
    (b) Two components of chromosomes.
    (c) The cell has changed shape.
    (d) The cell has a typical shape. 
    Ans. (a) Ribosomes in the surface of endoplasmic reticulum are associated with protein synthesis.
    (b) Two components of chromosomes are DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
    (c) The white blood cells present in our body can change their shape to move through narrow blood vessels.
    (d) Nerve cell has a typical shape.
31. Name:
    (a) The plastid involved in the conversion of green brinjal to violet.
    (b) The powerhouse of the cell.
    (c) Cell organelle is responsible for intercellular transport.
    (d) The functional unit of the gene. 
    Ans. (a) Chromoplast of plastid gives colour to the flower and fruits so it involved in the conversion of green brinjal to violet.
    (b) Mitochondria is the powerhouse of the cell. The energy required for various chemical activities needed for life is released by mitochondria in the form of ATP  molecules.
    (c) The endoplasmic reticulum is a large network of membrane-bound tubes and responsible for intercellular transport.
    (d) The functional unit of the gene is cistron which is a segment of DNA that encodes for the formation of protein molecules.
32. How does a living cell perform the basic functions?
    Ans. There is a division of labour in multicellular organisms in human beings. The different parts of the human body perform different functions. due to different organs like heart to pump blood, a stomach to digest food lungs for respiration and etc. Similarly, the division of labour is also seen within a single cell and each such cell has got certain specific components within it known as cell organelles. Each kind of cell organelle performs a special function, such as making new material in the cell, cleaning of the waste material from the cell and etc. A cell is able to live and perform all its functions because of these organelles. These organelles together constitute the basic unit called the cell. 

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