Chapter: 03. The Cell
Fill in the blanks.
A cell is the basic unit of structure and functions of all living organisms. The term ‘cell’ was coined by Robert Hooke. The shape of cells is related to the functions they perform. An egg of ostrich is about 15-20 cm in diameter. Organisms formed of one cell only are called unicellular organisms. A. Multiple Choice Questions
Which organelle is surrounded by two membranes? The smallest cells of human body are Animal cell differs from the plant cell in the absence of B. Assertion-Reason Type Questions
Assertion [A]: Mitochondria are described as powerhouse of the cell.
Reason [R]: Mitochondria provide energy to the cell by the oxidation of glucose. (a) Both Assertion [A] and Reason [R] are true. Assertion [A]: Chloroplasts are yellow in colour due to the presence of chlorophyll.
Reason [R]: Chromoplasts help to trap energy from sunlight for photosynthesis. (b) Both Assertion [A] and Reason [R] are false. Assertion [A]: Unicellular organisms are microscopic animals.
Reason [R]: Unicellular organisms are formed of single cell only. (d) Assertion [A] is false but Reason [R] is true. Assertion [A]: Vacuole pushes the nucleus towards periphery of the cell.
Reason [R]: Vacuole is present only in animal cells. (c) Assertion [A] is true but Reason [R] is false. C. Fill in the blanks with suitable words.
Red blood cells are the smallest cells in our body. Microscope is used to study structure of cell. All life processes of the cell take place in cytoplasm. The cavity of vacuole is filled with cell sap. Nucleus is the control centre of the cell. D. State whether the following statements are true or false. If false, rewrite the correct form of statements.
Nucleus contains chromatin net and nucleoplasm. The cells observed by Robert Hooke in a slice of cork were living cells. False. The cells observed by Robert Hooke in a slice of cork were dead cells, which were actually empty spaces surrounded by cellulose walls. The cheek cells are rectangular in shape. False. The cheek cells are polygonal or irregular in shape. Anton van Leeuwenhoek gave the cell theory. False. Schleiden and Schwann gave the cell theory. Cell wall is found in animal cells only. False. Cell wall is found in plant cells only. Leucoplasts give colour to the fruits. False. Chromoplasts give colour to the fruits. E. Give one word for the following.
The nonliving covering around plasma membrane in a plant cell The scientist who coined the term ‘cell’ The process of colouring the cells Plastids that give colour to flowers and fruits The control centre of the cell Rounded body present in the nucleoplasm The network of chromatin material Organelle that traps solar energy for photosynthesis F. Give reasons for the following.
Cells have different shapes. Cells have different shapes because their shape is directly related to the specific functions they perform. For example, nerve cells are long and branched to transmit signals over long distances, while red blood cells are biconcave discs to maximize oxygen transport. Plasma membrane is described as selectively permeable membrane. Plasma membrane is described as a selectively permeable membrane because it allows only certain substances (like oxygen, water, and nutrients) to enter and leave the cell, while preventing other substances from passing through freely. This controlled movement is essential for maintaining the cell’s internal environment. G. Encircle the odd one out and give reasons for your choice.
Chloroplasts, chromoplasts, chromatin, leucoplasts Chromatin is the odd one out because it is a component of the nucleus (genetic material), whereas chloroplasts, chromoplasts, and leucoplasts are types of plastids (organelles involved in photosynthesis or storage) found in the cytoplasm of plant cells. Nucleoplasm, cytoplasm, chromatin, nucleolus Chromatin is the odd one out because it is a component within the nucleus (genetic material), while nucleoplasm and nucleolus are other parts of the nucleus, and cytoplasm is the jelly-like substance outside the nucleus but within the cell membrane. All others are fluid or structural components of the main cellular compartments, while chromatin is the genetic material. Yeast, bacteria, fish, Amoeba Fish is the odd one out because it is a multicellular organism, whereas Yeast, bacteria, and Amoeba are all unicellular organisms. Nerve cells, muscle cells, guard cells, blood cells Blood cells is the odd one out because it is a general term encompassing both red blood cells and white blood cells, which have very different shapes and functions (RBCs are disc-shaped, WBCs are amoeboid). The other options (nerve cells, muscle cells, guard cells) describe specific cell types with distinct, relatively uniform shapes. (Alternatively, one could argue ‘guard cells’ as the odd one out because they are plant cells, while the others are animal cells, but “blood cells” as a category is broader than the specific cell types listed for animals). Based on shape and function, nerve, muscle, and guard cells are specific types with characteristic shapes, while blood cells are a broader category. H. Differentiate between the following.
Unicellular organism and multicellular organism
Chloroplast and chromoplast
Plant cell and animal cell
I. Match the columns.
J. Answer these questions.
Why does our body need new cells? Our body needs new cells for growth, to repair wounded tissues, and to replace old and worn out cells. This continuous process, known as cell division, is vital for maintaining the body’s health and functions. Why is the cell called the basic unit of structure and function of living organisms? The cell is called the basic unit of structure because all living organisms are made up of cells, much like a building is made of bricks. It is the basic unit of function because all essential life processes such as growth, metabolism, and reproduction occur within cells. Give salient features of the cell theory. The salient features of the cell theory are: Cells are the structural and functional units of all living organisms. New cells arise by the division of pre-existing cells. What is cell sap? What does it contain? Cell sap is the liquid that fills the cavity of the large central vacuole in plant cells. It contains water, dissolved sugars, salts, amino acids, pigments, and waste products. What are plastids? Name different types of plastids and their functions. Plastids are a type of organelle found only in plant cells. The different types of plastids and their functions are: Chloroplasts: Green-coloured plastids containing chlorophyll, responsible for photosynthesis (making food). Chromoplasts: Coloured plastids (red, yellow, orange) that give colours to flowers and fruits. Leucoplasts: Colourless plastids that store starch, proteins, and fats. Why are chloroplasts found only in plant cells? Explain. Chloroplasts are found only in plant cells because they contain chlorophyll, the pigment essential for photosynthesis. Photosynthesis is the process by which plants convert light energy into chemical energy (food). Animals do not perform photosynthesis and therefore do not require chloroplasts. Why is the nucleus called the control centre of the cell? The nucleus is called the control centre of the cell because it directs and regulates all the activities of the cell. It contains the cell’s genetic material (DNA in chromatin), which carries the instructions for cell growth, metabolism, protein synthesis, and reproduction. Give functions of vacuole in plant cell. In plant cells, the vacuole has several important functions: It stores water, organic compounds, pigments, and waste products. It helps maintain turgor pressure against the cell wall, which provides rigidity and mechanical support to the plant cell, helping the plant stand upright. Why is cell division essential? Cell division is essential for all living organisms because new cells are formed by this process to: Aid in the growth and development of the body. Repair wounded or damaged tissues. Replace old and worn-out cells, ensuring the continuous functioning of tissues and organs. Draw the cells of onion peel as seen under microscope. What are their features? (Drawing would show rectangular, brick-shaped cells arranged side-by-side, each with a distinct cell wall, a large central vacuole, a thin layer of cytoplasm, and a nucleus often pushed to one side.) Features of onion peel cells: They are typically brick-shaped or rectangular. They have a rigid cell wall surrounding the cell membrane. A large, prominent central vacuole is usually present, occupying most of the cell volume. The cytoplasm forms a thin lining between the cell wall and the vacuole. A nucleus is present, often located towards the periphery due to the large vacuole. K. Diagram-based Questions
Look at the following diagram and answer the questions.
(a) Label the parts marked A to F.
* A: Plasma membrane (or Cell membrane)
* B: Rough endoplasmic reticulum
* C: Nucleus
* D: Smooth endoplasmic reticulum
* E: Lysosome (or Peroxisome)
* F: Mitochondrion
(b) How do you identify whether this is a plant cell or an animal cell?
* This is an animal cell because it lacks a cell wall, plastids (like chloroplasts), and a large central vacuole, which are characteristic features of plant cells. It also shows centrioles and lysosomes, typically found in animal cells.
© Name the part which acts as the control centre of the cell.
* C (Nucleus) acts as the control centre of the cell. L. Subject Integration-Chemistry
Cellulose, found in the plant cell wall is organic compound composed of as many as 677 glucose units strung together. More than half carbon in plants is in the form of cellulose, cotton is over 90 per cent cellulose. Infer whin physical property you think makes cellulose 1080 for helping plants survive on land.
The physical property of cellulose that makes it ideal for helping plants survive on land is its rigidity and strength. Cellulose forms strong, rigid fibers that provide structural support to plant cells, allowing them to withstand gravity and maintain their upright shape on land. This rigidity also helps protect the plant cell from physical stress and prevents it from bursting due to excessive water uptake, which is crucial for terrestrial environments. M. Wordsearch
Find the names of six cell organelles from th word maze given below:
The six cell organelles found are: NUCLEUS (though often considered a main part of the cell, it is also referred to as a “major organelle” in some contexts, and it is present in the word search). 
Answers to textbook exercises
The six cell organelles found are: