Cell The Unit Of Life Class 11 Ncert Pdf 2021 Download

Every plant and animal cells are made of organ systems, and organ systems are made up of organs. Organs are constructed by tissues, and tissues are made up of a cluster of cells. Since cells are autonomous structures capable of carrying out functions on their own, it is said that the cell is the basic unit of life.

The cell is a structural and functional unit of a living entity. This chapter provides details about cells, the composition of cells, etc. Some organisms possess a single cell, known as unicellular organisms, while some others are composed of multiple cells, referred to as multicellular organisms.

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Cells form the structure of an entity. A group of cells form a tissue, further an organ and ultimately an organ system. They perform fundamental functions and life processes such as respiration, digestion, excretion etc., in both unicellular and multicellular entities. They perform all the activities independently. Hence, cells are referred to as structural and fundamental units of life.

Question 8.

What is active transport?

Answer:

The movement of molecules across a membrane in cells against a concentration gradient with the help of ATP units is called active transport.

All living organisms are made up of basic building blocks that form the fundamental unit of life called cells. Be it plants, animals, or microorganisms; these simple biological units define all their structural and functional abilities. An in-depth analysis of the discovery of cells, who discovered cells and how, their types, components, functions, and much more is given in the 5th Chapter- The Fundamental Unit of Life in the CBSE class 9 syllabus of science. To make your learning experience wonderful, here are our fundamental unit of life class 9 notes.

Cells form the basic structure of an organism and a collection of similar cells that perform an organized function from a Tissue. Each tissue serves a particular purpose and can be combined with other tissues to form organs. These carry out essential life processes like metabolism, growth, reproduction, etc. in unicellular and multicellular organisms. Here are some examples of tissues and organs in plants and animals:

Regardless of the complexity as well as the type of organism, cells are mainly divided into two categories. Mentioned below is a distinction between the 2 major types of cells in our fundamental unit of life class 9 notes:

Now that you are through with the aforementioned components of the cell, let us now study the last one in detail in our fundamental unit of life class 9 notes. The cell organelles play a very important role in the functioning of the human body. Have a look at their explanations-

Hopefully, through this fundamental unit of life class 9 notes, you are well versed in this chapter of biology. Consult Leverage Edu experts for career counselling and have a better understanding of which career path to choose.

Cells constitute various components of plants and animals. A cell is the smallest unit of life and is capable of all living functions. Cells are the building blocks of life. This is the reason why cells are referred to as the basic structural and functional units of life. All cells vary in their shape, size, and activity they perform. In fact, the shape and size of the cell is related to the specific functions they perform.

Cell is the smallest unit of life, which is capable of all living functions. If the organisation of a cell is destroyed due to some physical or chemical influence, then the ability of the cell to perform all living functions such as respiration, nutrition, excretion, etc. would be affected.

Mitochondriaare known as the powerhouse of cells. Mitochondria create energy for the cell, and this process of creating energy for the cell is known as cellular respiration. Most chemical reactions involved in cellular respiration occur in the mitochondria. The energy required for various chemical activities needed for life is released by the mitochondria in the form of ATP (Adenosine triphosphate) molecules. For this reason, mitochondria are known as the powerhouse of cells.

Question 10.

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

Answer:

The cells are not only the building blocks of the body but also the functional units of life. In fact, the activities of an organism are the sum total of coordinated activities of its constituent cells. All new cells of an organism arise from the pre-existing ones and hence each cell has the same genetic information and is capable of giving rise to a complete individual. This potential of the cell is termed as totipotency. Each cell has several organelles and the cell performs all functions through these organelles present in the cytoplasm. Since most of the activities of an organism are present in miniature form in each and every cell, the cell can be called a functional unit of life.

Question 14.

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

Answer:

Each chromosome bears genes the units of hereditary information and shows a constricted part called the centromere. Every chromosome essentially has a primary constriction of the centromere on the sides of which disc-shaped structures called kinetochores are present. Based on the position of the centromere the chromosomes can be classified into four types: The metacentric chromosome has a middle centromere forming two equal arms of the chromosome.

NCERT SolutionsImportant Questions NotesMCQ Sample Questions Sample Papers Class IX Science

NCERT Solutions for Fundamental unit of life1. Who discovered cells and how? (page 59) Answer- Cell was discovered by an English Botanist, Robert Hooke in 1665. He used self-designed microscope to observe cells in a cork slice back then.2. Why the cell is called the structural and functional unit of life? (Page 59) Answer- Cells are called the structural and functional unit of life because all the living organisms are made up of cells and all the functions that take place inside the organisms are performed by cells.1. How do substances like CO2 and water move in and out of the cell? Discuss. (page-61) Answer- The substances like CO2and water move in and out of a cell through the process called diffusion from the region of concentrated region to low concentrated one. When the concentration of carbon di-oxide and water is higher in external environment than that inside the cell, CO2and water moves inside the cell. When the concentration outside the cell is low but it is high inside the cell, they move outwards.2. Why the plasma membrane is called a selectively permeable membrane? (page 61) Answer- Plasma membrane called a selectively permeable membrane because it regulates the movement of substances from within to outside of the cell. This means that the plasma membrane allows the entry of some substances while preventing the movement of some other substance.1. Can you name the two organelles we have studied that contain their own genetic material? (page-65) Answer- Mitochondria and plastids their own genetic material2. If the organization of a cell is destroyed due to some physical or chemical influence, what will happen? (page 65) Answer- If the organization of a cell is destroyed due to some physical or chemical influence then cell will not be able to perform its basic functions like digestion, excretion, respiration etc. This may stop all the life activities and the life of an individual may come to an end.3. Why are lysosomes known as suicide bags? (page 65) Answer- Lysosomes are called suicide bags because in case of any disturbance of their cellular metabolism they release their own enzymes to digest their own cell.4. Where are proteins synthesized inside the cell? (page 65) Answer- The proteins are synthesized in the Ribosome EXERCISE (page 66)1. Make a comparison and write down ways in which plant cells are different from animal cells.Answer Animal cell Plant cellHas a cell wall.Has cell wall made up of cellulose.It does not contain chloroplast.It contains chloroplast.It has centrosome.It does not has centrosome.Vacuoles are smaller in size.Vacuoles are larger in size.Lysosomes are larger in number.Lysosomes are absent or very few in numberProminent Golgi bodies are present.Subunits of Golgi bodies are present.2. How is a prokaryotic cell different from a eukaryotic cell?Answer Prokaryotic cell Eukaryotic cellMost prokaryotes are unicellular.Most eukaryotes are multi-cellular.Size of the cell - (0.5- 5 ).Size of the cell - (50- 100 ).It contains a single chromosome.It contains more than one chromosome.Nucleolus is absent.Nucleolus is present.Membrane-bound cell organelles such as plastids, mitochondria, endoplasmic reticulum, Golgi apparatus, etc. are absent.Cell organelles such as mitochondria, plastids, endoplasmic reticulum, Golgi apparatus, lysosomes, etc. are present.Cell division occurs through binary fissionCell division occurs by mitosis.3. What would happen if the plasma membrane ruptures or breaks down? Answer- If ever the plasma membrane ruptures or breakdown then the cell will not be able to exchange material from its surroundings by diffusion. As a result of it the protoplasmic material will disappear and the cell will die.4. What would happen to the life of a cell if there was no Golgi apparatus? Answer- Golgi apparatus performs the function of a storage modification and packaging of products. If Golgi apparatus is not there then materials synthesized by cell will not be packaged and transported.5. Which organelle is known as the powerhouse of the cell? Why? Answer- Mitochondria are known as the powerhouse of cells because energy required for various chemical activities needed to support life is released by mitochondria in the form of ATP (Adenosine triphosphate) molecules.6. Where do the lipids and proteins constituting the cell membrane get synthesized? Answer- Lipids are synthesized in Smooth endoplasmic reticulum and the proteins are synthesized in endoplasmic reticulum.7. How does an Amoeba obtain its food? Answer- Amoeba obtains food using temporary finger-like extensions on the cell surface which fuse over the food particle forming a food-vacuole. Complex substances are broken down into simpler ones inside the food vacuole which then diffuse into the cytoplasm. The remaining undigested material is moved to the surface of the cell and thrown out resulting in excretion.8. What is osmosis? Answer- Osmosis is the process in which water molecules moves from the region of high concentration to a region of low concentration through a semi permeable membrane.