NCERT Solutions for Class 9 Science Chapter 5

NCERT Solutions for Class 9 Science Chapter 5 The fundamental unit of life Page 59, Page 61, Page 63, Page 65 and Exercises in English Medium updated for new academic session 2020-21 based on latest NCERT Books.

Hindi Medium versions of Chapter 5 पेज 66 के उत्तर or पेज 68 के उत्तर or पेज 70 के उत्तर or पेज 73 के उत्तर and अभ्यास के प्रश्न उत्तर are also available in PDF form to free download. Download NCERT Solutions 2020-21 and NCERT Solutions Apps for all subjects based on latest NCERT Books 2020-2021. We have updated our contents for CBSE, UP Board, Gujrat Board, MP Board and other boards who are following latest CBSE Syllabus 2020-21.

NCERT Solutions for Class 9 Science Chapter 5

Class:	9
Subject:	Science – विज्ञान
Chapter 5:	The fundamental unit of life

9th Science Chapter 5 Answers in English & Hindi Medium

NCERT Solutions for Class 9 Science Chapter 5 The fundamental unit of life Intext questions as well as end exercise question answers are given below for new academic session 2020-21. To solve your doubts, please join the Discussion Forum and ask the questions. Current users as well as our experts will reply you very soon. Download NCERT Solutions Offline Apps 2020-21 for offline use.

Why are stem cell used in treatment of severe immunodeficiency disorder (SCID) in the children? Give three reasons.

(i) These are capable of dividing for long periods to generate replacement for the cell which that cannot produce adenosine deaminase.
(ii) Stem cells can trigger immune response.
(iii) Stem cells can differentiate into white blood cells against the infectious diseases.

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

A cell is a smallest part of the living organisms which is fully alive and is capable of performing basic processes of life like, reproduction and respiration, therefore, it is called the structural and functional unit of life.

Name a single cell which may constitute a whole organism. What are they called?

Amoeba, They are called Unicellular organism.

Every multi-cellular organism has come from a single cell. Justify the statement.

Single cell forms a zygote which is first cell formed after fertilization. It further leads to the formation of large number of cells by cell division.

Which functions are performed by a single cell organism like amoeba?

A single cell takes in food, excrete waste, move, grow and reproduce.

Who discovered the cell and how?

Robert Hooke saw the cork which resembled the structure of a honey comb consisting of many little compartments. He observed these through a microscope. He called these boxes as cell.

Why is plasma membrane called a selective permeable membrane?

It is because it allows only certain material to pass through it and not all the materials.

Can you name the two organelles which contains their own genetic material?

(i) Mitochondria
(ii) Chloroplast

Questions for Practice on 9th Science Chapter 5

Question 1:
How do substances like carbon dioxide and water moves in and out of the cell? Discuss.
Answer 1:
It takes place through diffusion from higher concentration to lower concentration across a cell membrane.

Question 2:
Where are proteins synthesized inside the cell?
Answer 2:
Packaging, storage and dispatching of the materials, synthesized inside the cell will not take place.

Question 3:
What will happen when a human red blood cells is placed in hypertonic salt/sugar solution?
Answer 3:
It will shrink, i.e., plasmolysis will take place.

Important Questions on 9th Science Chapter 5

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

Plasma membrane is a selectively permeable membrane of the cell that maintains its homeostasis, i.e., constant internal composition of the cell. If it ruptures or breaks down the constant internal chemical composition of the cell will be lost and it will not be able to perform its basic functions. Such a cell with ruptured plasma membrane is killed.

कोशिका की खोज किसने और कैसे की?

कोशिका की खोज सर्वप्रथम राबर्ट हुक ने की। उन्होंने 1665 में कॉर्क की पतली छीलन को अपने बनाए गए सूक्ष्मदर्शी में देखा जिसमें मधुमखी के छत्ते जैसे छोटी छोटी कोठरियाँ दिखायी दी जिन्हे उन्होंने (सेल) कोशिका नाम दिया।

What would happen to the life of a cell if there is no Golgi apparatus?

The materials synthesized in the ER are stored, sorted, modified, packaged and dispatched to various targets inside and outside the cell through the Golgi apparatus packs products in vesicles, the secretary vesicles. In some cases complex sugars e.g. cellulose, may be made from simple sugars in Golgi apparatus. The Golgi apparatus is also involved in the formation of the cells which will not be possible if Golgi apparatus is not there.

Which organelle is known as the powerhouse of the cell? Why?

Mitochondria are known as the powerhouse of the cell because they contain enzymes that are needed for stepwise oxidation of food stuffs (carbohydrate, fats and lipids) present in the cells to CO2 and water. Oxidation of food releases energy which is used to form high-energy ATP (adenosine triphosphate) molecules. ATP is known as Energy Currency of the cell and it is used as cellular fuel. Energy stored in ATP is used to bring about energy requiring activities of the cell such as photosynthesis, protein synthesis and muscle contraction.

Where do the lipids and proteins constituting the cell membrane get synthesised?

Rough Endoplasmic Reticulum (RER) – synthesizes proteins constituting cell membrane.
Smooth Endoplasmic Reticulum (SER) – synthesizes lipids constituting cell membrane.

कोशिका को जीवन की संरचनात्मक व क्रियात्मक इकाई क्यों कहते हैं?

सभी जीवों का शरीर अत्यंत छोटी- छोटी कोशिकाओं से बना होता है, इसलिए इसे जीवों की संरचनात्मक इकाई कहते हैं। एक जीवित कोशिका वो सभी मूलभूत क्रिया (श्वसन, पाचन, उत्सर्जन) कर सकती है जो जीवन के लिए आवश्यक होती हैं, इसीलिए कोशिका को क्रियात्मक इकाई कहते है।

CO2 तथा पानी जैसे पदार्थ कोशिका से कैसे अंदर तथा बहार जाते हैं? इस पर चर्चा करें।

CO2 तथा पानी जैसे पदार्थ सामान्यतः विसरण द्वारा प्रकार कोशिका झिल्ली से अंदर बाहर आते जाते रहते है। जैसे: जब CO2 की सांद्रता कोशिका के अंदर बढ़ जाती है तो बाह्य पर्यावरण में CO2 की सांद्रता कोशिका में स्थित CO2 की सांद्रता की अपेक्षा कम होती है। उसी समय उच्च सांद्रता से निम्न सांद्रता की ओर विसरण द्वारा CO2 कोशिका से बाहर निकल जाती है। इसी प्रकार जब कोशिका में ऑक्सीजन की सांद्रता कम हो जाती है तो बाहर से O2 कोशिका में विसरण द्वारा अंदर चली जाती है।

प्लैज़्मा झिल्ली को वर्णात्मक पारगम्य झिल्ली क्यों कहते हैं?

प्लैज़्मा झिल्ली का एक विशिष्ट गुण होता है जिसके कारण वह कुछ चुने हुए पदार्थ को कोशिका के अंदर बाहर आने जाने देती है। इस तरह प्लाज्मा अवांछित पदार्थ को रोक देती है, इसीलिए इसे वर्णात्मक पारगम्य झिल्ली कहते हैं।

How does Amoeba obtain its food?

Amoeba has flexible cell membrane. It enables amoeba to engulf in food by the process called endocytosis.

What is osmosis?

The diffusion of water or solvent through a semi-permeable membrane from a solution of lower concentration of solutes to a solution of higher concentration of solutes, to which the membrane is relatively impermeable, is called osmosis.

यदि किसी कोशिका का संगठन किसी भौतिक अथवा रासायनिक प्रभाव के कारण नष्ट हो जाता है, तो क्या होगा?

कोशिका जीवन की सबसे छोटी इकाई है, जो सभी जीवित कार्यों में सक्षम है। अगर किसी भौतिक या रासायनिक प्रभाव के कारण कोशिका का संगठन नष्ट हो जाता है, तो कोशिका के सभी जीवित कार्यों जैसे श्वसन, पोषण, उत्सर्जन आदि प्रभावित होंगे। कोशिका अपना कार्य नहीं कर पायेगी और नष्ट हो जाएगी।

लाइसोसोम को आत्मघाती थैली क्यों कहते हैं?

लाइसोसोम के अंदर अत्यंत शक्तिशाली पाचक रस होते है जो कोशिका के अंदर प्रवेश करने वाले विषाक्त, विजातीय पदार्थो को तो नष्ट करते ही है, कोशिका के ठीक से कार्य न करने वाले अंगको को भी नष्ट करके उसे साफ करने का कार्य करते है। कभी-कभी पूरी कोशिका ही बीमार हो जाती है और ठीक से कार्य नहीं करती, तब पूरी कोशिका को ही नष्ट करने के लिए, लाइसोसोम फट जाते हैं और एंजाइम अपनी ही कोशिकाओं को पाचित कर देते हैं। इसलिए लाइसोसोम को कोशिका की आत्मघाती थैली भी कहते हैं।