NCERT solution for class 9th //Science // Chapter 5 - The fundamental unit of life

 NCERT solution  > Class 9th  > Science >Chapter 5 The fundamental unit of life 

NCERT solution for class 9th //Science  // 

Chapter 5 -   The fundamental unit of life 

                Page number 59 

Q1. Who discovered cells and how ? 

Answer  .- Robert hook was discovered cell in 1665 he observed the cell in a thin slice of cork .He appeared like a small compartment when he viewed through the microscope

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

 Answer   A cell have a capability in carrying out all the fly functions like nutrition and respiration x-ray excretion circulation etc hence it is called functional unit of life. The cell is the smallest unit of life and all living beings are made up of cells so it is a structural unit of life

                    Page number 61

Q3. How do substances like CO2 and water move in and out of the cell ? discuss 

Answer. - CO2 is move in and out of the cell because of the diffusion process it takes place up to the cell attain the concentration of equilibrium. The movement of water molecules through semipermeable membrane is called osmosis. Moment of water molecules from higher concentration to lower concentration

Q4. Why is the plasma membrane called a selectively permeable membrane 

Answer  -Plasma membrane allows the some selected substance inside or outside the cell hence it is called selectively permeable membrane or semi permeable membrane

                Page number 63

Q5. Fill in the gaps in the following table illustrating differences between prokaryotic and eukaryotic cell 

Prokaryotic Cell	Eukaryotic  Cell
a)     Size: Generally small (1-10µm) b)    Nuclear region ----and known as----- c)     Chromosome : single d)    Membrane bound cell organelles are absent	a)     Size: Generally large( 5 -100 µm) b)    Nuclear region: Well defind and surrounded by nuclear membrane c)     More than one chromosome d)    ------------

Answer-

                 

Prokaryotic Cell	Eukaryotic  Cell
a)     Size: Generally small (1-10µm) b)    Nuclear region poorly defined due to absence of nuclear membrane and known as nucleoids c)     Chromosome : single d)    Membrane bound cell organelles are absent	a)     Size: Generally large( 5 -100 µm) b)    Nuclear region: Well defined and surrounded by nuclear membrane c)     More than one chromosome d)    Membrane bound cell organelles are Present

                Page number 65 

Q6 . Can you name the two organelles we have studied that contain their own genetic material 

Answer - Chloroplast and mitochondria contain their own genetic material

Q7 . If the organization of a cell is destroyed due to some physical or chemical influence what will happen ?

Answer  -  If a cell is destroyed due to some physical or chemical influence the cell will die . Because all parts of the cell are responsible for the various function and they work together to continue the life .

Q8 . Why are lysosomes known as suicide bags ? 

Answer  - Lysosome contain some digestive enzyme if the lysosome rupture the enzymes are released in the cell cytoplasm and it digested all the content of the cell as a result the cell death due to this lysosome are known as suicidal bags of cell 

Q9 . Where are proteins synthesized inside the cell ?

Answer- Protein synthesized in the ribosome so ribosome are also known as protein factories

                        Exercise 

Q1. Make a comparison and write down ways in which plants are different from animal cell 

Answer  

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

Answer  

Q3. What would happen if the plasma membrane ruptures or breakdown .

Answer - Plasma membrane is outer protective covering of the cell organelles and cytoplasm it also provide a container to the cell organelles if the plasma membrane rupture down then the content of the cell exposed to the external environment and the cell become lethal 

Q4. What would happen to the life of a cell if there was no Golgi apparatus 

Answer  -  Golgi apparatus is responsible for the formation of many substance like polysaccharides , glycoprotein , lysosomes . It also helpful for the packages of many material synthesized by cell . all these work disturb if there is no Golgi apparatus

Q5. Which organelles is known as the powerhouse of the cell why ?

Answer  - Mitochondria is known as the powerhouse of the cell because the cellular respiration takes place in mitochondria and the energy released after that it also stored in mitochondria in the form of ATP .  ATP is called energy currency of the cell

Q6. Where do the lipids and proteins constituting the cell membrane get synthesiZed ?

Answer - Lipids are synthesized in endoplasmic reticulum and protein is synthesized in ribosomes which are usually present on the rough endoplasmic reticulum

Q7 . How does an amoeba obtain its food ?

Answer -  Amoeba obtain its food  by the process of phagocytosis the cell membrane of the amoeba have a numerous finger like outgrowth call pseudopodia these pseudopodia around the food particles and makes a food vacuole after engulfing the food

Q8 . What is osmosis ? 

Answer -  Osmosis is the process of movement of water molecules from the region of higher water concentration to lower water concentration through semipermeable membrane

Q9. Carry out the following osmosis experiment 

Take four peeled potato halves and scores each one out to make potato cups one of these potato carbs should be made from a boiled potato put each potato cup in a though containing water now 

a) Keep cup empty

 b) Put 1 teaspoon sugar in a cup B

c)  Put one teaspoon salt in a cup C 

 d)Put 1 teaspoon sugar in a boiled potato Cup D 

Sixth keep this for two hours then observe the four potato carbs and answer the following 

i) Explain why water gathers in the hollow 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  

Answer 

a) Water gathers in in empty portion of potato B and C because 

i) Plasma membrane of potato cells is living and acts as a semipermeable membrane 

ii) The higher concentration of water move in the empty portion of B and C 

iii) The water move in the empty portion of potato cups B and C by the process of osmosis 

b) potato Cup a is kept empty and it acts as a control setup 

c) i)  As a potato Cup is empty water does not gather in empty portion of A 

ii) In the potato Cup D the potato cell membrane lost its quality of semi permeability due to boiling so the movement of water does not occurs into potato cup D