NCERT Solutions For Class 9 Science Chapter 5 The Fundamental Unit Of Life
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NCERT Solutions For Class 9 Science Chapter 5 The Fundamental Unit Of Life on this step-by-step The Fundamental Unit Of Life answer guide . In some of State Boards and CBSE schools, students are taught thru NCERT books. As the chapter comes to an end, students are requested few questions in an exercising to evaluate their knowledge of the chapter. Students regularly want guidance dealing with those NCERT Solutions For Class 9 Science Chapter 5 The Fundamental Unit Of Life.
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NCERT Solution for Science –Chapter 5
The Fundamental Unit Of Life
Q. 1. Make a comparison and write down ways in which plant cells are different from animal cells .
Ans . Differences between a plant cell and an animal cell :
Q. 2. How is a prokaryotic cell different from a eukaryotic cell ?
Ans . Differences between prokaryotic cell and eukaryotic cell :
Q. 3. What would happen if the plasma membrane ruptures or breaks down ?
Ans . ( i ) Plasma membrane regulates the movement of substances inside and outside the cell .
( ii ) If it breaks down :
( a ) The cell will not be able to exchange materials from its surrounding by diffusion or osmosis .
( b ) The protoplasmic material of the cell will disappear which results in the death of the cell .
Q. 4. What would happen to the life of a cell if there was no Golgi apparatus ?
Ans . ( i ) Golgi apparatus consists of stacks of membrane bound vesicles . It is responsible for the storage , modification and packaging of substances manufactured in the cell .
( ii ) It also dispatches all the material synthesised near the endoplasmic reticulum to various targets inside and outside the cell .
( iii ) Thus , if there was no Golgi apparatus in the cell , then most activities performed by the Golgi apparatus will not take place .
Q. 5. Which organelle is known as the powerhouse of the cell ? Why ?
Ans . ( i ) Mitochondria are called the powerhouse of the cell .
( ii ) It releases the energy required for different chemical activities in the form of ATP molecules .
( iii ) ATP is known as the energy currency of the cell .
Q. 6 . Where do the lipids and proteins constituting the cell membrane get synthesised ?
Ans . ( i ) Lipids and proteins constituting the cell membrane get synthesised by the process of membrane biogenesis at SER and RER respectively .
( ii ) The SER helps in the manufacture of fat molecules , or lipids , important for cell function .
( iii ) The RER contains ribosomes which are attached to its surface . These ribosomes are present in all active cells and are responsible for manufacturing of protein .
Q. 7. How does an Amoeba obtain its food ?
Ans . ( i ) An Amoeba obtains its food by the process called endocytosis .
( ii ) Endocytosis is a process in which the flexibility of the cell membrane enables the cell to engulf in food and other material from its external environment .
( iii ) Amoeba takes food with the help of pseudopodia . Pseudopodia are finger – like extension of cell surface . These pseudopodia fuse to form food vacuole . Food is digested in food vacuole and then diffuses into the cytoplasm . The undigested food moves on surface and is then thrown out .
Q. 8. What is osmosis ?
Ans . ( i ) Osmosis is the process in which water moves from a region of its higher concentration to a region of its lower concentration through a semi permeable membrane .
( ii ) Through osmosis , the plasma membrane allows or permits the entry and exit of some materials in and out of the cell .
( iii ) When a cell is placed in a hypotonic solution the cell swells due to osmosis .
Q. 9. 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 2 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 ) In the hollowed portions of B and C , water gathers due to osmosis because in the surrounding medium the concentration of water is high .
( ii ) Potato A is necessary for this experiment because it acts as a control set – up . No water gathers in the hollowed portions of potato A. It is because , its cells have a selectively permeable membrane , which allows or permits the entry and exit of some mat rials in and out of the cell by osmosis .
( iii ) Water does not gather in the hollowed – out portions of A and D because cup A is empty and there is no difference in concentration of water hence no osmosis will take place . Whereas in cup D , due to boiling of potato , its selectively permeable membrane has been destroyed . Therefore , osmosis will not occur and no water will enter the boiled potato cup .
Q. 10 . Which type of cell division is required for growth and repair of body and which type is involved in formation of gametes ?
Ans . Mitosis is used for growth and repair of body . It produces diploid cells identical to each other and the parent cell . Meiosis is used for sexual reproduction and produces haploid cells different to each other and the parent cell . Thus , meiosis results in formation of gametes .
Q. 1. Who discovered the cells , and how ? [ NCERT Q. 1 , Page 59 ]
Ans . ( i ) Cell was first discovered by Robert Hooke in 1665 .
( ii ) He observed thin slices of cork slice ( a part of bark of a tree ) under a primitive microscope and saw honeycomb – like structures which look like tiny empty compartments .
( iii ) He called those compartments as cells , which is the basic structural and functional units of all living organisms .
Q. 2. Why is the cell called the structural and functional units of life ? [ NCERT Q. 2 , Page 59 ]
Ans . The cell is called the basic structural and functional units of life because :
( i ) All living organisms , whether plants or animals , are made up of cell .
( ii ) All the biochemical , genetic and physiological functions taking place inside the body are carried out by cells .
Q. 3. How do substances like CO₂ and water move in and out of the cell ? Discuss . [ NCERT Q. 1 , Page 61 ]
Ans . Movement of carbon dioxide ( CO₂ ) :
( i ) Transport of CO₂ across the membrane takes place through diffusion . In the external environment of the cell , the concentration of CO₂ is lower than inside the cell .
( ii ) It moves out of the cell from a region of high concentration to the region of low concentration .
Movement of water ( H₂O ) :
( i ) The process involved in movement water molecules is called osmosis .
( ii ) Osmosis is the passage of water from a region of high water concentration to a region of low water concentration through a semi – permeable membrane .
Q. 4. Why is the plasma membrane called a selectively permeable membrane ? [ NCERT Q. 2 , Page 61 ]
Ans . ( i ) Plasma membrane is the outermost covering of the cell . It separates the contents of the cell from outer environment .
( ii ) It is called selectively permeable membrane as it regulates the entry and exit of some materials in and out of the cell as well as it prevents movement of some other important materials .
Q. 5. Fill in the gaps in the following table illustrating differences between prokaryotic and eukaryotic cells .
[ NCERT Q. 1 , Page 63 ]
Ans . Prokaryotic cell :
( ii ) Nuclear region : Poorly defined because of the absence of a nuclear membrane , and is known as Nucleoid .
Eukaryotic cell :
( iv ) Membrane bound cell organelles such as nucleus , mitochondria etc. are present .
Q. 6 . Can you name the two organelles we have studied that contain their own genetic material ? [ NCERT Q. 1 , Page 65 ]
Ans . ( i ) Cell organelles that contain their own genetic material ( DNA ) and ribosomes are mitochondria and plastid .
( ii ) These organelles can synthesise their own protein and genetic material , hence they are also called as strange organelle .
Q. 7. If the organisation of a cell is destroyed due to some physical or chemical influence , what will happen ? [ NCERT Q. 2 , Page 65 ]
Ans . ( i ) Cell is the basic functional and structural units of the all living organisms .
( ii ) If the organisation of a cell is destroyed due to some physical or chemical influences :
( a ) the capability of the cell to perform various activities such as respiration and excretion , etc. will get disturbed .
( b ) This may stop all the life activities and may result in its death .
Q.8 . Why are lysosomes known as suicidal bags ? [ NCERT Q.3 , Page 65 ]
Ans . ( i ) Lysosomes are called suicidal bags because they contain hydrolytic digestive enzymes which are synthesised by endoplasmic reticulum .
( ii ) These enzymes have the ability to digest the cell’s own material when damaged or dead .
Q. 9 . Where are proteins synthesised inside the cell ? [ NCERT Q. 4 , Page 65 ]
Ans . ( i ) Proteins are synthesised in ribosomes inside the cell .
( ii ) Ribosomes are very small structures found either in a free state , suspended in the cytoplasm , or attached to the surface of the endoplasmic reticulum .
Benefits of NCERT Solutions For Class 9 Science Chapter 5 The Fundamental Unit Of Life
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