NCERT Solutions Class 11 Biology Chapter 8 Cell – The Unit of Life Syllabus 2022-23 - Oswal Publishers (2023)

Chapter 8 Cell – The Unit of Life

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1. Which of the following is not correct?

(a) Robert Brown discovered the cell.

(b) Schleiden and Schwann formulated the cell theory.

(c) Virchow explained that cells are formed from pre-existing cells.

(d) A unicellular organism carries out its life activities within a single cell.

Ans. (a) Robert Brown discovered the cell.

2. New cells generate from:

(a) bacterial fermentation

(b) regeneration of old cells

(c) pre-existing cells

(d) abiotic materials

Ans. (c) pre-existing cells

3. Match the following:

(Video) NCERT/Chapter 8/Cell:-The Unit Of Life/Class 11/Quick Revision Series/NEET/AIIMS/Biology/2019

Column I Column II
(a) Cristae (i) Flat membranous sacs in stroma
(b) Cisternae (ii) Infoldings in mitochondria
(c) Thylakoids (iii) Disc-shaped sacs in Golgi apparatus

Ans. The correct match is as follows:

Column I Column II
(a) Cristae (ii) Infoldings in mitochondria
(b) Cisternae (iii) Disc-shaped sacs in Golgi apparatus
(c) Thylakoids (i) Flat membranous sacs in stroma

4. Which of the following is correct:

(a) Cells of all living organisms have a nucleus.

(b) Both animal and plant cells have a well defined cell wall.

(c) In prokaryotes, there are no membrane bound organelles.

(d) Cells are formed de novo from abiotic materials.

Ans. (c) In prokaryotes, there are no membrane bound organelles.

5. What is a mesosome in a prokaryotic cell? Mention the functions that it performs.

Ans. Mesosome is a special membrane bound structure, which is formed by the extension of the plasma membrane in a prokaryotic cell.

Functions of Mesosome:

(a) It helps in cell wall formation, DNA replication and its distribution to the daughter cells.

(b) It also helps in respiration, secretion possesses, increases the surface area of the plasma membrane and enzymatic content.

6. How do neutral solutes move across the plasma membrane? Can the polar molecules also move across it in the same way? If not, then how are
these transported across the membrane?

Ans. Neutral solutes may move across the membrane by the process of simple diffusion along the concentration gradient.

(Video) Abnormal cells division #celldivison

The polar molecules cannot pass through the non-polar lipid bilayer of the membrane, they require a carrier protein to facilitate their transportation across the membrane. A few ions or molecules are transported across the membrane against their concentration gradient, i.e., from lower to the higher concentration. Such
a transport is an energy dependent process, in which ATP is utilised and is known as active transport, e.g., Na+/K+ pump.

7. Name two cell-organelles that are double membrane bound. What are the characteristics of these two organelles? State their functions
and draw labelled diagrams of both.

Ans. Chloroplasts and mitochondria are double membrane bound organelles.

Characteristics of Mitochondria:

(a) The mitochondria are sausage-shaped or cylindrical in shape having a diameter of 0.2-1.0 μm, average diameter of about 0.5 μm and length of 1.0-4.1 μm.

(b) The inner compartment is called the matrix and the outer membrane of mitochondria forms the continuous limiting boundary of the organelle.

(c) The inner membrane forms a number of infoldings called the cristae (single crista) towards the matrix. The cristae increases the surface area for absorption.

(d) The two membranes have their own specific enzymes associated with the mitochondrial function. The matrix of mitochonrdria also possesses single circular DNA molecule, a few RNA molecules, ribosomes (70 S) and the components required for the synthesis of proteins.

Functions of Mitochondria:

(a) Mitochondria are sites of aerobic respiration.

(b) They produce cellular energy in the form of ATP hence, they are called as power house of the cell.

NCERT Solutions Class 11 Biology Chapter 8 Cell – The Unit of Life Syllabus 2022-23 - Oswal Publishers (1)

Characteristics of chloroplasts:

(a) A number of organized flattened membranous sacs called thylakoids are present in the stroma.

(b) The space bounded by the inner membrane of the chloroplast is called the stroma.

(c) Thylakoids are arranged in stacks-like the piles of coins called grana.

(d) In addition, there are flat membranous tubules called the stroma lamellae connecting the thylakoids of the different grana.

(e) The stroma of the thy lakoids enclose a space called a lumen.

Functions of Chloroplasts:

(a) Chloroplasts are plant cell organelles that convert light energy into chemical energy via the process of photosynthesis. By doing so, they sustain life on Earth.

(b) Chloroplasts also provide diverse metabolic activities for plant cells, including the synthesis of fatty acids, lipids, etc.

NCERT Solutions Class 11 Biology Chapter 8 Cell – The Unit of Life Syllabus 2022-23 - Oswal Publishers (2)

(Video) Science Chapter-5 Fundamental Unit of Life - Cell | Important Notes of Class 9 Chapterwise |

8. What are the characteristics of prokaryotic cells?

Ans. Characteristics of prokaryotic cells:

(a) A prokaryotic cell is surrounded by a cell membrane. The cell wall in turn is surrounded by a slimy layer.

(b) It lacks membrane bound cell organelles such as chloroplast, mitochondria and golgi apparatus.

(c) The true nucleus with nuclear membrane and nucleolus are absent.

(d) The cytoplasm is filled with dense granules. Most of these granules are ribosomes.

9. Multicellular organisms have division of labour. Explain.

Ans. In multicellular organisms, cell is the basic structural and functional unit. The cells are organised to form tissues of blood, bone, etc. These tissues are further organised to form organs like heart, kidney, etc. The organs then organise to form organ systems such as digestive system, reproductive system and respiratory system, and the various organ systems of organism get arranged to form a complete individual. Hence, a specific group of cells performs the specific functions. Similarly, there are different functions that are carried out by different groups of cells and this is known as division of labour in multicellular organisms.

10. Cell is the basic unit of life. Discuss in brief.

Ans. The cell is the structural and functional unit of life because certain organisms complete their life cycle as a single cell. They are called unicellular or acellular organisms, e.g., Amoeba, Chlamydomonas, bacteria and yeast. In other organisms, the single cell undergoes divisions to form multicellular body. Body of human being, is made up of trillion of cells. All the cells of an organism carry the same genetic material, develop from same pre-existing cells and possess several organelles to perform various life activities. Thus the cells are therefore, basic unit of life.

11. What are nuclear pores? State their function.

Ans. Nuclear pores are tiny holes present in the nuclear membrane of the nucleus. They are formed by the fusion of two nuclear membranes.
These nuclear pores allow specific substances to be transferred into a cell and out from it. They allow molecules such as RNA and proteins to move in both directions, between the nucleus and the cytoplasm.

12. Both lysosomes and vacuoles are endomembrane structures, yet they differ in terms of their functions. Comment.

Ans. Both lysosomes and vacuoles are covered by a single membrane. Both of them perform different types of functions. Lysosomes contain hydrolysing enzymes and can hydrolyse all types of organic substances, except cellulose.

They perform phagocytic function. Therefore, they are also known as suicidal bags. The vacuoles are non-cytoplasmic sacs which are also covered by a membrane. The sap vacuoles store sap or water with dissolved organic and inorganic substances. They maintain osmotic pressure or turgidity of the cell. Thus, both lysosomes and vacuoles are endomembranous structures but differ from each other in the functions which, they perform.

(Video) Class 9 Biology Chapter 1 | The Fundamental Unit of Life Full Chapter Explanation

13. Describe the structure of the following with the help of labelled diagrams.

(a) Nucleus

(b) Centrosome

Ans. (a) Nucleus: The nucleus is a double membrane bound structure. It regulates the cellular activities of the cell. It constitutes the following parts:
1. Nuclear membrane: It is a double membrane separating the contents of the nucleus from the cytoplasm. The narrow space between the two membranes is called the perinuclear space. The nuclear membrane has tiny holes called nuclear pores. These holes allow specific substances to be transferred into the nucleus and out of it.

2. Nucleoplasm/Nuclear matrix: It is a homogenous granular fluid present inside the nucleus. It contains the nucleolus and chromatin. The nucleolus is a spherical structure that is not bound by any membrane. It is rich in protein and RNA molecules and is the site of ribosome formation. Chromatin is thread-like structures containing DNA and some basic proteins called histones.

NCERT Solutions Class 11 Biology Chapter 8 Cell – The Unit of Life Syllabus 2022-23 - Oswal Publishers (3)

(b) Centrosome: It is an organelle usually containing two cylindrical structures called centrioles. They are surrounded by amorphous pericentriolar materials. Both the centrioles in a centrosome lie perpendicular to each other in which each has an organisation like that of the cartwheel. They are made up of nine evenly spaced peripheral fibrils of tubulin. There is a proteinaceous hub in the central part of a centriole which is connected with tubules of the peripheral triplet by radial spokes made of protein. The centriole form the basal bodies of cilia or flagella and spindle fibres that give rise to spindle apparatus during cell division in animal life.

NCERT Solutions Class 11 Biology Chapter 8 Cell – The Unit of Life Syllabus 2022-23 - Oswal Publishers (4)

14. What is a centromere? How does the position of centromere form the basis of classification of chromosomes. Support your answer with a diagram showing the position of centromere on different types of chromosomes.

Ans. The centromere is a constriction present on the chromosomes where the chromatids are held together. Chromosomes are divided into four types based on the position of the centromere.

(a) Metacentric chromosome: The chromosomes in which the centromere is present in the middle and divides the chromosome into two equal arms is known as a metacentric chromosome. During anaphase, they appear V-shaped.

(b) Sub-metacentric chromosome: The chromosome in which the centromere is slightly away from the middle region is known as a sub-metacentric chromosome. In this, one arm is slightly longer than the other. During anaphase, they appear L-shaped.

(c) Acrocentric chromosome: The chromosome in which the centromere is located close to one of the terminal ends is known as an acrocentric chromosome. In this, one arm is extremely long and the other is extremely short. During anaphase, they appear J-shaped.

(d) Telocentric chromosome: The chromosome in which the centromere is located at one of the terminal ends is known as a telocentric chromosome. During anaphase, they appear I-shaped.

NCERT Solutions Class 11 Biology Chapter 8 Cell – The Unit of Life Syllabus 2022-23 - Oswal Publishers (5)


Which is the hardest chapter in biology class 11? ›

The chapters related to cells and cell division are most difficult because its very hard to remember the differece between miosis and mitosis,g-phase otherwise, everything is quite interesting and easily understandable.

Which is the most important chapter in biology class 11? ›

The cell division and cell cycle, plant kingdom, animal kingdom, locomotion and movement, anatomy of flowering plants, and the structural organisation in plants are the most important ones.

What is the name of Chapter 8 in Class 11 biology? ›

NCERT Solutions Class 11 Biology Chapter 8 Cell The Unit of Life.

What is cell unit of life class 11 notes? ›

A cell is a unit of living that can live by itself and includes all living organisms and tissues of the body. It consists of three major parts: the cell membrane, nucleus, and cytoplasm. In addition to surrounding the cell, the cell membrane is in charge of deciding which substances can get into and leave the cell.

Is science harder 11 and 12? ›

11th is very different in terms of the course content as compared to what you have studied till 10th. Difficulty level is higher if you have chosen the science stream as now it is no more general science. 11th grade will teach you concepts of fundamental physics, chemistry, biology, maths etc.

Which class is harder class 11 or 12? ›

You will find class 12th syllabus easier as compare to class 11th. And, entrances exams also contains about 60% weightage from class 11th.

Is 11th Biology hard? ›

Is Biology 11 difficult? Ans. Many students choose Biology because they believe it is a simple and engaging topic. However, after students examine the extensive curriculum for class 11, they know that getting decent grades in this subject would take some effort.

What is the hardest chapter in Biology? ›

I think photosynthesis, food, respiration, sexual reproduction in plants and humans are the longest and/or hardest. Enzymes has a lot of info that is included in other chapters such as monera. I personally find biochemistry (photosynthesis and respiration) the most difficult.

Is there 97 chapters in NEET? ›

There are altogether 97 topics in NEET Physics, Chemistry & Biology syllabus. Divide them according to the complexity and make your study-plan.

Which chapters are deleted biology class 11? ›

Biology Deleted Syllabus for Class 11 Practical

Study of osmosis by potato osmometer. Study of plasmolysis in epidermal peels (e.g. Rhoeo/lily leaves or flashy scale leaves of onion bulb). Comparative study of the rates of transpiration in the upper and lower surface of leaves.

Which chapter should I start first in class 11 biology? ›

The Living World is an important introductory chapter in Class 11 Biology. It covers very basic yet important concepts that will be repeatedly mentioned in the upcoming chapters as well. It touches upon topics like what is living, the diversity in living organisms and also explains taxonomy and taxonomical aids.

How many types of cells are there? ›

There are about 200 different types of cells in the body. Here are just a few examples: red blood cells (erythrocytes) skin cells.

What is unit cell very short answer? ›

The unit cell is defined as the smallest repeated unit with full crystal structure symmetry. The unit cell geometry is known as a parallelepiped, providing six lattice parameters taken as the lengths of the edges of the cells (a, b , c) and the angles between them (α, β, ÿ).

What is cell the structural and functional unit of life class 11? ›

A cell is capable of carrying out all life processes, such as nutrition, excretion, respiration, etc. Hence it is called as the functional unit of life. The cell is the smallest unit of life and all the living beings are made up of cells. Hence a cell is called the structural unit of life.

How to score 90 percent in class 11 science? ›

Strategies you should follow to score above 90% in CBSE Board Exams 2022
  1. Make a good study plan. ...
  2. Small-scale study. ...
  3. Prepare notes. ...
  4. Categorize the important areas. ...
  5. Revise your work daily. ...
  6. Textbooks study. ...
  7. Practice mock papers and previous years' papers. ...
  8. Eat healthy and nutritious food.
Feb 2, 2023

How can I become topper in class 11? ›

11 Habits to Become a Topper
  1. Regularly Attending Classes. ...
  2. “If you fail to plan, you are planning to fail.” ...
  3. Understand More and Cram Less. ...
  4. Regular Revision. ...
  5. “Practise Makes a Man Perfect.” ...
  6. Say No to Last Moment Exam Preparations. ...
  7. Get Interested in What You Are Studying. ...
  8. Learn From Your Mistakes.

Which subject is hardest in class 11? ›

Which is the hardest subject in 11th?
  • 1 Physics. For the majority of people, physics is very tough because it is applying numbers to concepts that can be very abstract. ...
  • 2 Foreign Language. ...
  • 3 Chemistry. ...
  • 4 Calculus. ...
  • 5 Math. ...
  • 6 English. ...
  • 7 Biology. ...
  • 8 Trigonometry.

Can you get failed in class 11? ›

If if you get fail in your 11th standard science stream exam then you will have to give the supplementary exam of of the specific subject in which you have filled and then you will pass then after you will appear for class 12th but you have to give the supplementary exam after failing, you have to study the failed ...

Is Class 12 is easier than class 11 in NEET? ›

Weightage of Class 11 and 12 in NEET

According to some teachers and previous years NEET papers, class 12 has slightly higher weightage than class 11 in NEET as the number of questions asked from 12th syllabus are more than 11th. But it's not always the case with every NEET exam.

How many hours should I study in class 11? ›

So, starting in 11th grade, 4 to 5 hours of study will be beneficial for JEE.

Is biology the hardest major? ›

Broadly speaking, biology is a comparatively simple science major to get into without a huge amount of training or expertise in the subject. One advantage students and professors will point out is that there is less complex mathematics to do in biology compared to your average science class in another subject.

How to score full marks in Biology Class 11? ›

Read the concepts in detail from the NCERT Class 11 books of Physics, Chemistry, and Biology. Write down the crucial terms, short descriptions, diagrams, flow charts, scientific names, etc. Practice them regularly so that you don't forget them till exams.

How to pass in class 11? ›

Although the basic criteria to pass class 11 in each subjects of the science stream is about to score at least 21 in all of the subjects out of 70, as per the state board marking rules. However in other boards as well in class 11 you need to score at least 30% marks in each and every subjects.

What is the hardest chapter in biology? ›

I think photosynthesis, food, respiration, sexual reproduction in plants and humans are the longest and/or hardest. Enzymes has a lot of info that is included in other chapters such as monera. I personally find biochemistry (photosynthesis and respiration) the most difficult.

Is class 11 biology tough? ›

Is Biology 11 difficult? Ans. Many students choose Biology because they believe it is a simple and engaging topic. However, after students examine the extensive curriculum for class 11, they know that getting decent grades in this subject would take some effort.

Which topic is hard in biology? ›

Protista, Monera, and Virus were the first, second, and third most difficult topics in X grade. Genetics, Immune System, and Metabolism also selected into three topics of all grades that were considered most difficult by undergraduate students majoring in Biology.

What are the most difficult topics in biology? ›

Some concepts and topics in biology that are considered difficult by students include protein synthesis, respiration and photosynthesis, cell division (mitosis and meiosis), hormone regulation, oxygen transport, nervous system, and genetic manipulation.

Is biology easy or hard? ›

Biology can be complicated, but it is also very interesting if you take a step back to think about what you're studying. Having the right attitude can make it more fun to study. It will still be difficult, but if you're interested in what you're learning, it won't feel like such a burden.

Is biology so easy? ›

Anyone can learn biology, but it's not always easy. Biology doesn't require as much math as physics or astronomy, but it can still be challenging to understand biological systems and processes. One of the keys to effective learning of biology is to master general concepts before tackling specific ones.

Is math or biology harder? ›

But in comparison between both of them,maths is harder than biology because to solve the question of maths,an person have to do good practice of questions..

Why is biology so hard? ›

The difficulty in learning biology is because there are concepts that are abstract, complex, and use concepts that are based on memorization (Cimer, 2012) . Even though learning biology requires thinking high levels such as HOTS and metacognitive (Madang, et al., 2019). ...

Is biology very hard? ›

So college biology classes may be more difficult than your average high school class. But, according to Draft, biology is a highly accessible subject, especially if you're really interested in it. You don't need to come into an introductory biology class with a specific knowledge base or level of talent.

What is the most difficult science to study? ›

Chemistry is famous for being one of the hardest subjects ever, so it's no surprise that a Chemistry degree is fiercely challenging. Just one topic in Chemistry (for example, organic chemistry) is incredibly complex.


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