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Chapter Analysis
Intermediate16 pages • EnglishQuick Summary
In Chapter 8, 'Cell: The Unit of Life', the focus is on understanding cells as the fundamental units of life. It provides a historical overview of cell theory and examines the differences between prokaryotic and eukaryotic cells. Key cellular components such as cell membranes, organelles, and the nucleus are comprehensively described. The chapter emphasizes the structural and functional organization of cells in living organisms and promotes understanding of cell division and related processes.
Key Topics
- •Cell theory and its historical development
- •Structure and function of prokaryotic and eukaryotic cells
- •Cell membrane and the fluid mosaic model
- •Organelles and their roles in cells
- •Differences between plant and animal cells
- •Cell division and genetic material
- •Mechanisms of cellular transport
- •Endomembrane system and its functions
Learning Objectives
- ✓Understand the basic principles of cell theory.
- ✓Differentiate between prokaryotic and eukaryotic cells.
- ✓Identify the structure and function of cellular organelles.
- ✓Explain the organization of plants and animal cells.
- ✓Comprehend the processes involved in cellular transport.
- ✓Appreciate the significance of the structural unit of life, the cell.
Questions in Chapter
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.
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New cells generate from (a) bacterial fermentation (b) regeneration of old cells (c) pre-existing cells (d) abiotic materials
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Match the following Column I: (a) Cristae (b) Cisternae (c) Thylakoids with Column II: (i) Flat membranous sacs in stroma (ii) Infoldings in mitochondria (iii) Disc-shaped sacs in Golgi apparatus
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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.
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What is a mesosome in a prokaryotic cell? Mention the functions that it performs.
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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?
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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.
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What are the characteristics of prokaryotic cells?
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Multicellular organisms have division of labour. Explain.
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Cell is the basic unit of life. Discuss in brief.
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What are nuclear pores? State their function.
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Both lysosomes and vacuoles are endomembrane structures, yet they differ in terms of their functions. Comment.
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Describe the structure of the following with the help of labelled diagrams. (i) Nucleus (ii) Centrosome
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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.
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Additional Practice Questions
Describe the differences between prokaryotic and eukaryotic cells with examples.
mediumAnswer: Prokaryotic cells are typically smaller and lack a true nucleus and membrane-bound organelles, while eukaryotic cells have a defined nucleus and organelles. Examples of prokaryotes include bacteria and archaea, while plants, animals, and fungi are eukaryotes.
Explain the structure and function of the plasma membrane.
mediumAnswer: The plasma membrane is composed of a phospholipid bilayer with embedded proteins. It functions to protect the cell and regulate the movement of substances in and out, providing sites for chemical reactions and cell recognition.
How do mitochondria contribute to cellular respiration?
mediumAnswer: Mitochondria are the powerhouse of the cell where aerobic respiration occurs. They convert energy stored in glucose into ATP through processes like the Krebs cycle and electron transport chain, essential for cellular activities.
Discuss the role of the endoplasmic reticulum in cells.
mediumAnswer: The endoplasmic reticulum (ER) is crucial for protein and lipid synthesis. Rough ER has ribosomes for protein synthesis, while Smooth ER is involved in lipid production and detoxification.
Illustrate the fluid mosaic model of cell membranes.
easyAnswer: The fluid mosaic model describes the cell membrane as a dynamic structure with a lipid bilayer hosting various proteins, which float freely, allowing for flexibility and interactions with the environment.
What is the significance of the Golgi apparatus in cells?
mediumAnswer: The Golgi apparatus modifies, sorts, and packages proteins and lipids for storage or transport out of the cell. It is crucial for processing cellular products.
Explain the structural differences between plant and animal cells.
mediumAnswer: Plant cells have a rigid cell wall, chloroplasts, and large central vacuoles, whereas animal cells have centrioles and lysosomes and lack a cell wall and chloroplasts.
What are ribosomes, and why are they important?
easyAnswer: Ribosomes are molecular machines made of RNA and protein found in all cells, crucial for synthesizing proteins according to genetic instructions.
How do lysosomes function in cellular digestion?
mediumAnswer: Lysosomes contain enzymes that break down waste materials, cellular debris, and foreign invaders like bacteria through phagocytosis.
Describe the role of chloroplasts in photosynthesis.
mediumAnswer: Chloroplasts are the site of photosynthesis in plant cells, converting light energy into chemical energy stored in glucose, with chlorophyll playing a key role in the capture of light energy.
NCERT Exemplar
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