Cell Structure and Function Introduction
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Questions and Answers

What is the smallest structural and functional unit of life?

A cell

Who coined the term 'cell' after observing dead cells in cork?

Robert Hooke

Who was the first to observe living cells in pond water?

Antony Van Leeuwenhoek

What is the living matter present inside the cell?

<p>Protoplasm</p> Signup and view all the answers

Who discovered the nucleus in a cell?

<p>Robert Brown</p> Signup and view all the answers

What is the principle that states that all cells arise from pre-existing cells?

<p>Omnis cellula e cellula</p> Signup and view all the answers

Describe the process of how a single cell develops into a fully formed organism.

<p>A single cell divides and redivides, then differentiates into different types, forming tissues, which then form organs, and eventually, the individual takes shape.</p> Signup and view all the answers

What was Robert Hooke's observation that led to his discovery of cells?

<p>He observed dead cells that resembled honeycomb-like structures in cork.</p> Signup and view all the answers

What was the significance of Antony Van Leeuwenhoek's discovery?

<p>He was the first to observe living cells in pond water.</p> Signup and view all the answers

What is the importance of the discovery of the nucleus in a cell?

<p>The discovery of the nucleus helped in understanding the cell's internal structure and function.</p> Signup and view all the answers

What is the term used to describe the living matter present inside a cell?

<p>Protoplasm.</p> Signup and view all the answers

What is the significance of Rudolf Virchow's discovery?

<p>He established that all cells arise from pre-existing cells.</p> Signup and view all the answers

What is the significance of the observation made by Robert Hooke in cork cells?

<p>Hooke's observation led to the discovery of cells and paved the way for further research in cell biology.</p> Signup and view all the answers

How did the discovery of the nucleus contribute to our understanding of cellular structure?

<p>The discovery of the nucleus by Robert Brown revealed the presence of a control center in cells, which is responsible for regulating cellular activities.</p> Signup and view all the answers

What is the importance of the concept that 'all cells arise from pre-existing cells' in understanding cellular development?

<p>The concept highlights the continuity of life and underscores the idea that cells give rise to cells, forming a continuous chain of life.</p> Signup and view all the answers

What role do cells play in the formation of tissues and organs?

<p>Cells differentiate and specialize to form tissues, which in turn form organs, ultimately giving rise to a fully formed organism.</p> Signup and view all the answers

What is the significance of J.E.Purkinje's contribution to the field of cell biology?

<p>Purkinje introduced the term 'protoplasm' to describe the living matter inside cells, highlighting the dynamic and living nature of cellular content.</p> Signup and view all the answers

What was the significance of Antony Van Leeuwenhoek's observation of living cells in pond water?

<p>Van Leeuwenhoek's observation marked the first time living cells were observed, revealing the diversity of cellular life.</p> Signup and view all the answers

Who formulated the cell theory?

<p>M. Schleiden and T. Schwann</p> Signup and view all the answers

What is the significance of the cell theory?

<p>The cell is the basic structural and functional unit of life; all organisms are composed of cells.</p> Signup and view all the answers

What is the process of observing plant cells?

<p>Observing onion peel cells under a compound microscope</p> Signup and view all the answers

What is the significance of the discovery of the electron microscope?

<p>Made it possible to observe and understand the complex structure of cells and their organelles</p> Signup and view all the answers

What is the shape of epidermal cells of onion peel?

<p>Regularly arranged linear or rectangular compartments</p> Signup and view all the answers

What is the effect of the central vacuole on the nucleus?

<p>Pushed towards the periphery</p> Signup and view all the answers

Who expanded the cell theory?

<p>Rudolf Virchow</p> Signup and view all the answers

What is the significance of the cell as the basic unit of life?

<p>All organisms are composed of cells</p> Signup and view all the answers

What is the purpose of staining onion peel cells with safranin?

<p>To visualize the cells under a microscope</p> Signup and view all the answers

What is the significance of observing onion peel cells?

<p>To study the structure and function of cells</p> Signup and view all the answers

What is the significance of the cell theory in understanding the structure and function of living organisms?

<p>The cell theory is significant because it states that all living organisms are composed of cells, which are the basic structural and functional units of life, and that all cells arise from pre-existing cells.</p> Signup and view all the answers

What is the purpose of using a compound microscope to observe onion peel cells?

<p>The purpose of using a compound microscope to observe onion peel cells is to examine the structure of the cells, including the cell walls and nucleus, in detail.</p> Signup and view all the answers

How did the discovery of the electron microscope contribute to our understanding of cellular structure?

<p>The discovery of the electron microscope made it possible to observe and understand the complex structure of cells and their organelles at the ultrastructural level.</p> Signup and view all the answers

What is the role of the central vacuole in the structure of epidermal cells of onion peel?

<p>The central vacuole pushes the nucleus towards the periphery of the cell.</p> Signup and view all the answers

Why is it necessary to stain onion peel cells with safranin before observing them under a microscope?

<p>Safranin is used to stain onion peel cells to make their structures more visible under the microscope.</p> Signup and view all the answers

What is the significance of the observation that epidermal cells of onion peel are arranged in a regular, linear or rectangular pattern?

<p>The regular arrangement of epidermal cells of onion peel suggests that they are organized in a specific pattern to form the epidermal tissue.</p> Signup and view all the answers

What is the importance of M. Schleiden and T. Schwann's contributions to the field of cell biology?

<p>M. Schleiden and T. Schwann formulated the cell theory, which states that cells are the basic structural and functional units of life, and that all cells arise from pre-existing cells.</p> Signup and view all the answers

What is the purpose of using glycerine to mount onion peel cells on a microscope slide?

<p>Glycerine is used to mount onion peel cells on a microscope slide to preserve the cells and prevent them from drying out.</p> Signup and view all the answers

How did the discovery of the cell theory impact our understanding of the development and organization of living organisms?

<p>The cell theory provided a fundamental understanding of the development and organization of living organisms, and revealed that cells are the basic units of life.</p> Signup and view all the answers

What is the significance of the observation that the nucleus is pushed towards the periphery of the epidermal cells of onion peel?

<p>The observation that the nucleus is pushed towards the periphery of the epidermal cells of onion peel suggests that the central vacuole is large and occupies a significant portion of the cell volume.</p> Signup and view all the answers

What is the significance of the cell theory in understanding the structure and function of living organisms, and how does it relate to the discovery of the electron microscope?

<p>The cell theory is significant in understanding the structure and function of living organisms as it provides a fundamental understanding of the basic unit of life. The discovery of the electron microscope further expanded our understanding of cellular structure and function by enabling us to observe and study the complex structure of cells and their organelles.</p> Signup and view all the answers

How does the arrangement of epidermal cells of onion peel reflect the cell theory, and what does it reveal about the structure of these cells?

<p>The regular, linear or rectangular arrangement of epidermal cells of onion peel reflects the cell theory, which states that cells are the basic structural and functional units of life. This arrangement reveals that these cells are composed of rigid cell walls and have a central vacuole that pushes the nucleus towards the periphery.</p> Signup and view all the answers

What is the significance of staining onion peel cells with safranin, and how does it facilitate the observation of these cells under a microscope?

<p>Staining onion peel cells with safranin is significant because it enhances the visibility of the cell structures, allowing for better observation under a microscope. This facilitates the study of the morphology and arrangement of cells, which is essential for understanding cellular structure and function.</p> Signup and view all the answers

How does the central vacuole influence the position of the nucleus in epidermal cells of onion peel, and what does this reveal about the organization of cellular structures?

<p>The central vacuole in epidermal cells of onion peel pushes the nucleus towards the periphery, revealing the dynamic organization of cellular structures. This arrangement highlights the importance of cellular compartments in maintaining cellular function and structure.</p> Signup and view all the answers

What is the significance of the discovery of the electron microscope in expanding our understanding of cellular structure and function, and how does it relate to the cell theory?

<p>The discovery of the electron microscope enabled the observation of complex cellular structures and organelles, expanding our understanding of cellular structure and function. This discovery further supports the cell theory, which states that cells are the basic structural and functional units of life.</p> Signup and view all the answers

How does the observation of onion peel cells under a microscope demonstrate the principles of the cell theory, and what does it reveal about the structure and function of cells?

<p>The observation of onion peel cells under a microscope demonstrates the principles of the cell theory by showing that cells are the basic structural and functional units of life. This observation reveals the organization of cells, their composition, and their functional structures, such as the central vacuole and nucleus.</p> Signup and view all the answers

What is the significance of the cell theory in understanding the development and organization of living organisms, and how does it relate to the concept of cellular differentiation?

<p>The cell theory is significant in understanding the development and organization of living organisms because it provides a foundation for understanding cellular differentiation and the organization of tissues and organs. The cell theory highlights the importance of cells in development and organization, and how they differentiate to form specialized structures and functions.</p> Signup and view all the answers

How does the process of observing plant cells, as described in the text, demonstrate the principles of scientific inquiry, and what does it reveal about the nature of scientific investigation?

<p>The process of observing plant cells demonstrates the principles of scientific inquiry by involving systematic observation, experimentation, and data analysis. This process reveals the importance of careful observation, experimentation, and critical thinking in scientific investigation, as well as the need for controlled conditions and precise techniques.</p> Signup and view all the answers

What is the significance of the contributions of M. Schleiden and T. Schwann to the field of cell biology, and how did their work lay the foundation for modern cellular biology?

<p>The contributions of M. Schleiden and T. Schwann were significant in establishing the cell theory, which laid the foundation for modern cellular biology. Their work recognized the importance of cells as the basic structural and functional units of life, and paved the way for further research into cellular structure and function.</p> Signup and view all the answers

How does the structure of epidermal cells of onion peel reflect the principles of cellular organization, and what does it reveal about the relationships between cellular components?

<p>The structure of epidermal cells of onion peel reflects the principles of cellular organization by demonstrating the arrangement of cellular components, such as the cell wall, central vacuole, and nucleus. This structure reveals the complex relationships between cellular components, highlighting the importance of cellular compartments and their interactions in maintaining cellular function.</p> Signup and view all the answers

What is the purpose of scraping the internal lining of the mouth with a clean toothpick or scapula?

<p>To obtain squamous epithelial cells.</p> Signup and view all the answers

What stain is used to stain the squamous epithelial cells?

<p>Methylene blue.</p> Signup and view all the answers

What is the shape of squamous epithelial cells of the cheek?

<p>Flat and polygonal.</p> Signup and view all the answers

What is the purpose of adding glycerine to the stained material?

<p>To mount the stained material on a microscope slide.</p> Signup and view all the answers

Why is it important not to scrape the cheek too hard?

<p>To avoid injuring the buccal mucosa.</p> Signup and view all the answers

What is the significance of observing squamous epithelial cells of the cheek?

<p>It confirms that the basic structural unit of life is the cell.</p> Signup and view all the answers

What is the importance of spreading the scrapped material uniformly on the slide?

<p>To ensure even staining and clear observation of the cells.</p> Signup and view all the answers

What is the significance of tapping the coverslip with the blunt end of a needle?

<p>To spread the cells evenly and remove air bubbles.</p> Signup and view all the answers

What is the purpose of using a clean toothpick or scapula to scrape the internal lining of the mouth?

<p>To collect squamous epithelial cells from the cheek for microscopic observation.</p> Signup and view all the answers

What is the function of methylene blue in the process of preparing a temporary stained slide?

<p>To stain the squamous epithelial cells.</p> Signup and view all the answers

Why is it necessary to wipe off the excess stain with a dropper or blotting paper?

<p>To prevent excessive staining and ensure clear visibility of the cells under the microscope.</p> Signup and view all the answers

What is the purpose of adding a drop of glycerine to the stained material?

<p>To mount the stained material on a microscope slide.</p> Signup and view all the answers

What is the significance of observing the cells under both low and high power of the microscope?

<p>To observe the cells at different magnifications and obtain a detailed understanding of their structure.</p> Signup and view all the answers

What is the shape of the squamous epithelial cells observed under the microscope?

<p>Flat and polygonal.</p> Signup and view all the answers

What is the importance of spreading the scrapped material uniformly on the slide?

<p>To ensure that the cells are evenly distributed and can be observed clearly.</p> Signup and view all the answers

What is the significance of the experiment in confirming the cell theory?

<p>It confirms that the basic structural unit of life is the cell.</p> Signup and view all the answers

What is the size of a normal human cell in diameter?

<p>20 um to 30 um</p> Signup and view all the answers

Which cell is the largest in animals?

<p>Ostrich egg</p> Signup and view all the answers

What is the shape of nerve cells?

<p>Elongated and branched</p> Signup and view all the answers

What is the diameter of the largest human cell, the female ovum?

<p>0.01 mm</p> Signup and view all the answers

What is the shape of red blood cells?

<p>Discoidal or saucer-shaped</p> Signup and view all the answers

What is the diameter of red blood cells?

<p>7.5 um</p> Signup and view all the answers

What is the range of diameter of a normal human cell?

<p>20 um to 30 um</p> Signup and view all the answers

What is the shape of a nerve cell?

<p>Elongated and branched</p> Signup and view all the answers

What is the largest cell in animals?

<p>Ostrich egg</p> Signup and view all the answers

What is the smallest cell in the human body?

<p>Red blood cell</p> Signup and view all the answers

What is the purpose of the shape of a cell?

<p>To perform a specific function</p> Signup and view all the answers

What is the unit of measurement used to measure the size of cells?

<p>Micrometers or microns (μm)</p> Signup and view all the answers

What is the relationship between the shape of cells and their functions?

<p>The shape of cells is often related to the different functions they perform.</p> Signup and view all the answers

What is the shape of human white blood cells and why is it important?

<p>Human white blood cells are amoeboid, which allows them to squeeze out through capillary walls.</p> Signup and view all the answers

What is the significance of the shape of red blood cells?

<p>Red blood cells are circular and biconcave, which allows them to move easily through small spaces and transport oxygen.</p> Signup and view all the answers

What is the shape of nerve cells and why is it important?

<p>Nerve cells are long, which allows them to conduct impulses from distant parts of the body to the brain and vice-versa.</p> Signup and view all the answers

What is the shape of muscle cells and why is it important?

<p>Muscle cells are long and contractile, which helps in the movement of bones.</p> Signup and view all the answers

What is the significance of the shape of xylem vessels?

<p>Xylem vessels are long and elongated, which helps in the conduction of water and minerals.</p> Signup and view all the answers

What determines the size of an organism?

<p>The size of an organism is dependent upon the number of cells, not on the size of the cell.</p> Signup and view all the answers

What is the shape of guard cells in plant leaves and why is it important?

<p>Guard cells are kidney-shaped, which allows them to open and close stomata to allow exchange of gases.</p> Signup and view all the answers

What shape are human white blood cells, and how does their shape relate to their function?

<p>Amoeboid; their amoeba-like movement with pseudopodia enables them to squeeze out through capillary walls.</p> Signup and view all the answers

What is the significance of the shape of red blood cells, and how does it enable them to perform their function?

<p>Circular and biconcave; this shape allows them to move easily through small spaces and transport oxygen.</p> Signup and view all the answers

What is the relationship between the shape of nerve cells and their function?

<p>Long; this shape enables them to conduct impulses from distant parts of the body to the brain and vice-versa.</p> Signup and view all the answers

How does the shape of muscle cells relate to their function, and what is the significance of this relationship?

<p>Long and contractile; this shape enables them to help in the movement of bones.</p> Signup and view all the answers

What is the significance of the shape of xylem vessels, and how does it enable them to perform their function?

<p>Long and elongated; this shape enables them to conduct water and minerals.</p> Signup and view all the answers

What is the relationship between the shape of guard cells and their function in plants?

<p>Kidney-shaped; this shape enables them to open and close stomata to allow exchange of gases.</p> Signup and view all the answers

What is the main difference between unicellular and multicellular organisms?

<p>Unicellular organisms consist of a single cell that performs all life processes, whereas multicellular organisms consist of multiple cells.</p> Signup and view all the answers

How does the size of an organism relate to the number of cells it has?

<p>The size of an organism is dependent upon the number of cells, not the size of the cell.</p> Signup and view all the answers

What is the term used to describe organisms made up of more than one cell?

<p>Multicellular organisms</p> Signup and view all the answers

What is the term used to describe the concept that cells in multicellular organisms are specialized to perform different functions?

<p>Division of labour</p> Signup and view all the answers

What is the basic structural and functional unit of life?

<p>Cell</p> Signup and view all the answers

What are the three main parts of a plant or animal cell?

<p>Cell membrane, cytoplasm, and nucleus</p> Signup and view all the answers

What is the purpose of cell specialization in multicellular organisms?

<p>To perform different functions in the body</p> Signup and view all the answers

What does the term 'cellula' refer to?

<p>A small box-like structure</p> Signup and view all the answers

What is the significance of the discovery of cells in understanding life?

<p>Cells are the basic structural and functional units of life</p> Signup and view all the answers

What is the main characteristic that differentiates multicellular organisms from unicellular organisms?

<p>Specialization of cells to perform different functions due to division of labor.</p> Signup and view all the answers

What is the structure that Robert Hooke observed in cork and named 'cellula'?

<p>Box-like structures</p> Signup and view all the answers

What are the three main parts of plant and animal cells?

<p>Cell membrane, Cytoplasm, and Nucleus</p> Signup and view all the answers

What is the significance of cell specialization in multicellular organisms?

<p>It allows different cells to perform different functions of the body.</p> Signup and view all the answers

What is the functional unit of life?

<p>The cell</p> Signup and view all the answers

What is the role of cells in multicellular organisms?

<p>They perform different functions due to specialization.</p> Signup and view all the answers

Why are cells important in understanding the structure and function of living organisms?

<p>Because cells are the basic structural and functional units of life.</p> Signup and view all the answers

What is the living substance of a cell?

<p>Protoplasm</p> Signup and view all the answers

What is the function of the plasma membrane?

<p>It protects the internal components of the cell, provides shape to the cell, and allows materials to enter and leave the cell.</p> Signup and view all the answers

What is the cell wall?

<p>An outer, non-living, and freely permeable layer found in plant cells.</p> Signup and view all the answers

What is the difference between nucleoplasm and cytoplasm?

<p>Nucleoplasm is the protoplasm found in the nucleus, while cytoplasm is the protoplasm found outside the nucleus.</p> Signup and view all the answers

What is the function of the cell membrane in regulating the movement of molecules?

<p>It allows certain molecules to pass through while regulating the passage of others.</p> Signup and view all the answers

What is the composition of the plasma membrane?

<p>It is made up of organic molecules called lipids and proteins.</p> Signup and view all the answers

What is the difference between the cell membrane and the cell wall?

<p>The cell membrane is a living, semi-permeable layer, while the cell wall is a non-living, freely permeable layer.</p> Signup and view all the answers

What is the function of the cell membrane in protecting the cell?

<p>It protects the internal components of the cell from the outside environment.</p> Signup and view all the answers

What is the significance of the cell membrane in providing shape to the cell?

<p>It helps maintain the cell's shape and structure.</p> Signup and view all the answers

What is the importance of the cell membrane in regulating the movement of molecules?

<p>It allows nutrients and essential elements to enter the cell, while waste materials leave the cell.</p> Signup and view all the answers

What is the functional unit of the cell where specific functions are performed?

<p>Cell organelle</p> Signup and view all the answers

What is the outer layer surrounding the plasma membrane in plant cells?

<p>Cell wall</p> Signup and view all the answers

What is the function of the plasma membrane in a cell?

<p>Protects the cell, provides shape, and regulates the movement of materials in and out of the cell</p> Signup and view all the answers

What is the name given to the portion of protoplasm found in the nucleus?

<p>Nucleoplasm</p> Signup and view all the answers

What is the term used to describe the living matter present inside a cell?

<p>Protoplasm</p> Signup and view all the answers

What is the function of the cytoplasm in a cell?

<p>Performs specific functions, provides shape, and supports the cell's metabolic activities</p> Signup and view all the answers

What is the role of the plasma membrane in regulating the movement of materials in and out of the cell?

<p>Allows nutrients to enter and waste materials to leave the cell</p> Signup and view all the answers

What is the composition of the plasma membrane?

<p>Organic molecules called lipids and proteins</p> Signup and view all the answers

What is the purpose of the cell wall in plant cells?

<p>Provides additional protection and support to the plant cell</p> Signup and view all the answers

What is the difference between nucleoplasm and cytoplasm?

<p>Nucleoplasm is found in the nucleus, while cytoplasm is found outside the nucleus</p> Signup and view all the answers

What is the function of cell organelles in the cytoplasm?

<p>Perform specific functions necessary for the cell's survival</p> Signup and view all the answers

What is the outer thick, protective layer of the cell found in bacterial and plant cells?

<p>Cell wall</p> Signup and view all the answers

What is the outer covering of the protoplasm found in plant and animal cells?

<p>Cell membrane</p> Signup and view all the answers

What is the fluid content inside the cell, excluding the nucleus, composed of?

<p>Matrix, organelles, and non-living inclusions like vacuoles and granules</p> Signup and view all the answers

What is the most important part of the living cell that controls all vital functions?

<p>Nucleus</p> Signup and view all the answers

What is the part of the protoplasm enclosed by the nuclear membrane?

<p>Nucleoplasm</p> Signup and view all the answers

What is the spherical body in the nucleus rich in proteins and RNA?

<p>Nucleolus</p> Signup and view all the answers

What is the darkly stained network of long and fine threads called?

<p>Chromatin threads</p> Signup and view all the answers

What is the function of the nuclear membrane?

<p>It controls the passage of materials between cytoplasm and nucleoplasm</p> Signup and view all the answers

What is the characteristic of the cell wall?

<p>Non-living and freely permeable</p> Signup and view all the answers

What is the characteristic of the cell membrane?

<p>Living and selectively permeable</p> Signup and view all the answers

What type of cells have a cell wall?

<p>bacterial and plant cells</p> Signup and view all the answers

What is the function of the cell membrane?

<p>to control the passage of materials</p> Signup and view all the answers

What is the fluid content of the cell called?

<p>cytoplasm</p> Signup and view all the answers

What is the most important part of the living cell?

<p>nucleus</p> Signup and view all the answers

What are the four components of the nucleus?

<p>nuclear membrane, nucleoplasm, nucleolus, and chromatin material</p> Signup and view all the answers

What is the function of the nuclear membrane?

<p>to control the passage of materials between cytoplasm and nucleoplasm</p> Signup and view all the answers

What is the part of the protoplasm inside the nuclear membrane called?

<p>nucleoplasm</p> Signup and view all the answers

What is the function of the nucleolus?

<p>to produce ribosomes</p> Signup and view all the answers

What is the term for the darkly stained network of threads in the nucleus?

<p>chromatin reticulum</p> Signup and view all the answers

What is the main difference between the cell wall and cell membrane?

<p>the cell wall is non-living and freely permeable, while the cell membrane is living and selectively permeable</p> Signup and view all the answers

What is the outer thick, protective layer of the cell found in bacterial and plant cells?

<p>Cell wall</p> Signup and view all the answers

What is the fluid content of the cell inner to the plasma membrane, excluding the nucleus?

<p>Cytoplasm</p> Signup and view all the answers

What is the most important part of the living cell that controls all vital functions?

<p>Nucleus</p> Signup and view all the answers

What is the part of protoplasm enclosed by the nuclear membrane?

<p>Nucleoplasm</p> Signup and view all the answers

What is the function of the nuclear membrane?

<p>It surrounds the nucleus and separates it from the cytoplasm, controlling the passage of materials.</p> Signup and view all the answers

What is the term for the darkly stained network of long and fine threads in the nucleus?

<p>Chromatin reticulum</p> Signup and view all the answers

What is the outer covering of the protoplasm?

<p>Cell membrane</p> Signup and view all the answers

What is the component of the nucleus that produces ribosomes?

<p>Nucleolus</p> Signup and view all the answers

What is the purpose of the nuclear membrane?

<p>To control the passage of materials between the cytoplasm and nucleoplasm.</p> Signup and view all the answers

What is the term for the fluid content of the cell inner to the plasma membrane, excluding the nucleus?

<p>Cytoplasm</p> Signup and view all the answers

What is the main function of the cell wall in plant and bacterial cells?

<p>To provide a thick, protective layer</p> Signup and view all the answers

What is the main difference between the cell wall and cell membrane?

<p>The cell wall is non-living and freely permeable, while the cell membrane is living and selectively permeable.</p> Signup and view all the answers

What is the composition of cytoplasm?

<p>Matrix, organelles, and non-living inclusions like vacuoles and granules</p> Signup and view all the answers

What are the four components of the nucleus?

<p>Nuclear membrane, nucleoplasm, nucleolus, and chromatin material</p> Signup and view all the answers

What is the function of the nuclear membrane?

<p>To separate the nucleus from the cytoplasm and control the passage of materials</p> Signup and view all the answers

What is the role of the nucleolus?

<p>To produce ribosomes</p> Signup and view all the answers

What is chromatin material composed of?

<p>Darkly stained network of long and fine threads called chromatin threads</p> Signup and view all the answers

What is the function of the cell membrane?

<p>To serve as the outer covering of the protoplasm</p> Signup and view all the answers

What is the difference between nucleoplasm and cytoplasm?

<p>Nucleoplasm is the part of protoplasm within the nucleus, while cytoplasm is the fluid content of the cell excluding the nucleus</p> Signup and view all the answers

What is the significance of the nucleus in a cell?

<p>It controls all the vital functions of the cell</p> Signup and view all the answers

What is the function of nucleopore?

<p>exchange of different substances between nucleoplasm and cytoplasm</p> Signup and view all the answers

What is the composition of chromosomes?

<p>DNA and proteins</p> Signup and view all the answers

What is the function of plastids in plant cells?

<p>manufacture and storage of important chemical compounds</p> Signup and view all the answers

What type of plastid is responsible for pigment synthesis and storage?

<p>chromoplasts</p> Signup and view all the answers

What is the main function of leucoplasts?

<p>storage of starch, proteins, and fats</p> Signup and view all the answers

Why do plant cells have a lower distribution of mitochondria compared to animal cells?

<p>energy is produced during photosynthesis</p> Signup and view all the answers

What is the role of chromoplasts in plant cells?

<p>involved in pigment synthesis and storage</p> Signup and view all the answers

What is the difference between prokaryotes and eukaryotes?

<p>presence or absence of a nucleus</p> Signup and view all the answers

What is the function of the cell wall in plant cells?

<p>provides structural support and protection</p> Signup and view all the answers

What is the primary function of plastids in plant cells?

<p>photosynthesis</p> Signup and view all the answers

What is the function of nucleopore?

<p>exchange of different substances between nucleoplasm and cytoplasm</p> Signup and view all the answers

What is the composition of chromosomes?

<p>DNA and proteins</p> Signup and view all the answers

What is the function of plastids?

<p>manufacture and storage of important chemical compounds</p> Signup and view all the answers

What is the characteristic of chromoplasts?

<p>red, yellow, or orange in color and involved in pigment synthesis and storage</p> Signup and view all the answers

What is the function of leucoplasts?

<p>store food prepared in the plant in the form of starch, proteins, and fats</p> Signup and view all the answers

Why do plant cells have a greater distribution of plastids than mitochondria?

<p>because energy is also produced during photosynthesis</p> Signup and view all the answers

What is the role of plastids in photosynthesis?

<p>responsible for pigment synthesis and storage and photosynthesis</p> Signup and view all the answers

What is the difference between prokaryotes and eukaryotes?

<p>presence or absence of a true nucleus</p> Signup and view all the answers

What is the function of the plasma membrane?

<p>selectively permeable, regulating the movement of substances in and out of the cell</p> Signup and view all the answers

What is the role of the cell wall in plant cells?

<p>provides structural support and protection to the cell</p> Signup and view all the answers

What is the significance of nucleopores in the nucleus?

<p>Nucleopores facilitate the exchange of different substances between the nucleoplasm and cytoplasm.</p> Signup and view all the answers

What is the main function of plastids in plant cells?

<p>Plastids are responsible for photosynthesis, storage of products like starch, and the synthesis and storage of pigments.</p> Signup and view all the answers

What is the difference between chromoplasts and leucoplasts?

<p>Chromoplasts are pigmented, whereas leucoplasts are colourless or white.</p> Signup and view all the answers

Why do plant cells have a greater distribution of plastids compared to mitochondria?

<p>Plant cells have a greater distribution of plastids because they produce energy through photosynthesis, whereas animal cells rely on mitochondria for energy production.</p> Signup and view all the answers

What is the role of DNA in the cell?

<p>DNA carries all genetic information, which is passed on to the next generation.</p> Signup and view all the answers

What is the significance of the nucleus in the cell?

<p>The nucleus contains most of the cell's genetic material, in the form of DNA.</p> Signup and view all the answers

What is the main difference between prokaryotes and eukaryotes?

<p>Prokaryotes lack a true nucleus, whereas eukaryotes have a true nucleus.</p> Signup and view all the answers

What is the function of the cell wall in plant cells?

<p>The cell wall provides support, shape, and protection to the cell.</p> Signup and view all the answers

What is the significance of selectively permeable membranes in cells?

<p>Selectively permeable membranes allow certain substances to pass through while blocking others.</p> Signup and view all the answers

What is the difference between the nuclear region and the cytoplasm?

<p>The nuclear region contains the genetic material, whereas the cytoplasm is the region outside the nucleus where metabolic processes occur.</p> Signup and view all the answers

What is the shape of chloroplasts?

<p>Disc-shaped</p> Signup and view all the answers

What is the function of the stroma in chloroplasts?

<p>Contains photosynthetic enzymes and starch grains</p> Signup and view all the answers

What is the purpose of the cell wall in plant cells?

<p>Provides protection</p> Signup and view all the answers

What is the function of ribosomes in cells?

<p>Protein synthesis</p> Signup and view all the answers

What is the main difference between prokaryotes and eukaryotes?

<p>Presence of a nuclear membrane</p> Signup and view all the answers

What is the purpose of the plasma membrane in cells?

<p>Regulates the movement of materials in and out of the cell</p> Signup and view all the answers

What are thylakoids in chloroplasts?

<p>Membrane-bound vesicles that contain chlorophyll</p> Signup and view all the answers

What is the function of the intergranal frets or lamellae in chloroplasts?

<p>Interconnects grana</p> Signup and view all the answers

What is the function of ribosomes in the cell?

<p>Ribosomes synthesize proteins</p> Signup and view all the answers

What is the term used to describe the ribosome?

<p>Protein factory of the cell or Engine of the cell</p> Signup and view all the answers

What is the function of the sap vacuole in plant cells?

<p>It stores food, salts, sugar, amino acids, and organic acids, and helps in maintaining turgidity and rigidity of the cell</p> Signup and view all the answers

What is the covering membrane of the sap vacuole called?

<p>Tonoplast</p> Signup and view all the answers

Where are proteins synthesized inside the cell?

<p>In the ribosomes</p> Signup and view all the answers

What is the function of the central vacuole in mature plant cells?

<p>It occupies 50-90% of the cell volume and helps in maintaining turgidity and rigidity of the cell</p> Signup and view all the answers

What is the fluid content of the vacuole called?

<p>Cell sap</p> Signup and view all the answers

What is the purpose of the sap vacuole in plant cells?

<p>It stores nutrients, helps in maintaining turgidity and rigidity of the cell, and is a dump for waste products</p> Signup and view all the answers

What is the function of ribosomes in a cell?

<p>Ribosomes function as enzymes or provide support for other cell functions, and are also known as the 'Engine of the cell'. They are responsible for protein synthesis.</p> Signup and view all the answers

What is the main function of sap vacuoles in plant cells?

<p>Sap vacuoles store salts, sugars, amino acids, organic acids, and some proteins, and also help in maintaining turgidity and rigidity of the cell.</p> Signup and view all the answers

What is the difference between free and bound ribosomes?

<p>Free ribosomes are found floating in the cytoplasm, while bound ribosomes are attached to the endoplasmic reticulum.</p> Signup and view all the answers

What is the function of the tonoplast in a sap vacuole?

<p>The tonoplast is the membrane that surrounds the sap vacuole and regulates the flow of materials in and out of the vacuole.</p> Signup and view all the answers

What is the name of the fluid content of a sap vacuole?

<p>The fluid content of a sap vacuole is called cell sap.</p> Signup and view all the answers

Where are proteins synthesized inside the cell?

<p>Proteins are synthesized inside the cell at the ribosomes.</p> Signup and view all the answers

What is the function of sap vacuoles in osmotic absorption of water?

<p>Sap vacuoles help in osmotic absorption of water by regulating the amount of water in the cell.</p> Signup and view all the answers

What is the term used to describe ribosomes?

<p>Ribosomes are often referred to as the 'protein factory' of the cell or the 'engine of the cell'.</p> Signup and view all the answers

What is the shape of chloroplasts and what is the function of the stroma in chloroplasts?

<p>Chloroplasts are usually disc-shaped, and the stroma contains a variety of photosynthetic enzymes and starch grains.</p> Signup and view all the answers

What is the difference between prokaryotes and eukaryotes?

<p>Prokaryotes are organisms whose cells lack a nuclear membrane and the genetic material lies freely in the form of nucleoid, whereas eukaryotes are organisms whose cells have a well-organized nucleus with a nuclear membrane.</p> Signup and view all the answers

What is the function of the cell wall in plant cells?

<p>The cell wall provides protection to the plant cell.</p> Signup and view all the answers

What is the function of ribosomes in the cell?

<p>Ribosomes are the protein builders or protein synthesizers of the cell.</p> Signup and view all the answers

What is the significance of the selective permeability of the plasma membrane?

<p>The selective permeability of the plasma membrane allows certain substances to pass through while keeping others out, which is essential for maintaining cellular homeostasis.</p> Signup and view all the answers

What is the structure of thylakoids in chloroplasts?

<p>Thylakoids are membrane-bound vesicles that are usually stacked in grana and contain the photosynthetic pigment chlorophyll.</p> Signup and view all the answers

What is the function of the intergranal frets or lamellae in chloroplasts?

<p>The intergranal frets or lamellae are tubular membranes that connect the grana and allow for the exchange of substances between them.</p> Signup and view all the answers

What is the difference between active and passive transport across the plasma membrane?

<p>Passive transport occurs through diffusion, whereas active transport requires energy and involves the movement of ions, sugars, amino acids, etc. across the plasma membrane.</p> Signup and view all the answers

What is the function of contractile vacuole in unicellular freshwater organisms?

<p>osmoregulation and excretion</p> Signup and view all the answers

What is the process by which a cell divides to form two new cells called?

<p>cell division</p> Signup and view all the answers

What is the term used to describe the specialization of cells to carry out particular functions in an organism?

<p>division of labour</p> Signup and view all the answers

What is the role of cell division in the growth of multicellular organisms?

<p>necessary for growth</p> Signup and view all the answers

What is the purpose of cell division in replacement of old cells?

<p>helps in replacement of old and worn-out cells</p> Signup and view all the answers

What is the importance of cell division in reproduction?

<p>essential for reproduction and birth of young ones</p> Signup and view all the answers

What is the role of cell division in repair?

<p>replaces damaged or worn-out cells</p> Signup and view all the answers

What is the concept where cells specialize to carry out particular functions within an organism?

<p>division of labour</p> Signup and view all the answers

What is the purpose of contractile vacuoles in unicellular freshwater organisms?

<p>Osmoregulation and excretion</p> Signup and view all the answers

What is the process by which a cell divides to form two new cells?

<p>Cell division</p> Signup and view all the answers

What is the importance of cell division in multicellular organisms?

<p>For growth, replacement of old cells, reproduction, and repair</p> Signup and view all the answers

What is the term used to describe the specialization of cells to carry out particular functions?

<p>Division of labour</p> Signup and view all the answers

What is the role of cell division in repairing damaged tissues?

<p>Replacement of old and worn-out cells</p> Signup and view all the answers

What is the significance of cell division in reproduction?

<p>Essential for reproduction and birth of young ones</p> Signup and view all the answers

What is the importance of cell division in replacing old cells?

<p>Helps in replacement of old and worn-out cells</p> Signup and view all the answers

How does cell division contribute to the growth of an organism?

<p>Necessary for growth</p> Signup and view all the answers

Study Notes

Cell-Structure and Function

  • Every organism starts life as a single cell, which divides and redivides to form tissues and eventually, organs.
  • Cells are the smallest structural and functional unit of life, visible only with a microscope.

Discovery of Cell

  • Robert Hooke (1665) observed dead cells resembling honeycomb-like structures in cork, and termed them as "cells".
  • Antony Van Leeuwenhoek (1674) was the first to observe living cells in pond water.
  • Robert Brown (1831) discovered the nucleus.
  • J.E.Purkinje (1839) coined the term "protoplasm" to describe the living matter present inside cells.
  • Rudolf Virchow (1855) established that all cells arise from pre-existing cells, stating "omnis cellula e cellula".

Cell-Structure and Function

  • Every organism starts life as a single cell, which divides and redivides to form tissues and eventually, organs.
  • Cells are the smallest structural and functional unit of life, visible only with a microscope.

Discovery of Cell

  • Robert Hooke (1665) observed dead cells resembling honeycomb-like structures in cork, and termed them as "cells".
  • Antony Van Leeuwenhoek (1674) was the first to observe living cells in pond water.
  • Robert Brown (1831) discovered the nucleus.
  • J.E.Purkinje (1839) coined the term "protoplasm" to describe the living matter present inside cells.
  • Rudolf Virchow (1855) established that all cells arise from pre-existing cells, stating "omnis cellula e cellula".

Cell-Structure and Function

  • Every organism starts life as a single cell, which divides and redivides to form tissues and eventually, organs.
  • Cells are the smallest structural and functional unit of life, visible only with a microscope.

Discovery of Cell

  • Robert Hooke (1665) observed dead cells resembling honeycomb-like structures in cork, and termed them as "cells".
  • Antony Van Leeuwenhoek (1674) was the first to observe living cells in pond water.
  • Robert Brown (1831) discovered the nucleus.
  • J.E.Purkinje (1839) coined the term "protoplasm" to describe the living matter present inside cells.
  • Rudolf Virchow (1855) established that all cells arise from pre-existing cells, stating "omnis cellula e cellula".

Cell Theory

  • Formulated by German biologists Matthias Schleiden (1838) and Theodor Schwann (1839)
  • States that the cell is the structural and functional unit of all living beings

Cell Theory Principles

  • The cell is the basic structural and functional unit of life
  • All organisms are composed of cells
  • All cells are produced by the division of pre-existing cells

Observing Plant Cells: Onion Peel Experiment

  • Peel a thin onion scale from the concave side to get a transparent, thin, and membranous onion peel piece (epidermis)
  • Place the peel in a watch glass containing water
  • Cut out a small portion of the peel and place it flat on a glass slide with a drop of water and a few brush strokes
  • Add a drop of safranin stain
  • Drain excess stain and mount the onion peel in a drop of glycerine under a coverslip
  • Examine the slide under low and high powers of a compound microscope

Observations of Onion Peel Cells

  • Epidermal cells are regularly arranged in linear or rectangular compartments with rigid cell walls
  • Nucleus is pushed towards the periphery due to the presence of a central vacuole

Discovery of Electron Microscope

  • Made it possible to observe and understand the complex structure of cells and their organelles (Knoll and Ruska, 1939)

Precautions for the Experiment

  • Immediately place the onion peel in a water-containing petri-dish to avoid folding and drying
  • Spread the peel uniformly on the slide
  • Drain excess stain
  • Ensure no air bubbles form under the coverslip

Cell Theory

  • Formulated by German biologists Matthias Schleiden (1838) and Theodor Schwann (1839)
  • States that the cell is the structural and functional unit of all living beings

Cell Theory Principles

  • The cell is the basic structural and functional unit of life
  • All organisms are composed of cells
  • All cells are produced by the division of pre-existing cells

Observing Plant Cells: Onion Peel Experiment

  • Peel a thin onion scale from the concave side to get a transparent, thin, and membranous onion peel piece (epidermis)
  • Place the peel in a watch glass containing water
  • Cut out a small portion of the peel and place it flat on a glass slide with a drop of water and a few brush strokes
  • Add a drop of safranin stain
  • Drain excess stain and mount the onion peel in a drop of glycerine under a coverslip
  • Examine the slide under low and high powers of a compound microscope

Observations of Onion Peel Cells

  • Epidermal cells are regularly arranged in linear or rectangular compartments with rigid cell walls
  • Nucleus is pushed towards the periphery due to the presence of a central vacuole

Discovery of Electron Microscope

  • Made it possible to observe and understand the complex structure of cells and their organelles (Knoll and Ruska, 1939)

Precautions for the Experiment

  • Immediately place the onion peel in a water-containing petri-dish to avoid folding and drying
  • Spread the peel uniformly on the slide
  • Drain excess stain
  • Ensure no air bubbles form under the coverslip

Cell Theory

  • Formulated by German biologists Matthias Schleiden (1838) and Theodor Schwann (1839)
  • States that the cell is the structural and functional unit of all living beings

Cell Theory Principles

  • The cell is the basic structural and functional unit of life
  • All organisms are composed of cells
  • All cells are produced by the division of pre-existing cells

Observing Plant Cells: Onion Peel Experiment

  • Peel a thin onion scale from the concave side to get a transparent, thin, and membranous onion peel piece (epidermis)
  • Place the peel in a watch glass containing water
  • Cut out a small portion of the peel and place it flat on a glass slide with a drop of water and a few brush strokes
  • Add a drop of safranin stain
  • Drain excess stain and mount the onion peel in a drop of glycerine under a coverslip
  • Examine the slide under low and high powers of a compound microscope

Observations of Onion Peel Cells

  • Epidermal cells are regularly arranged in linear or rectangular compartments with rigid cell walls
  • Nucleus is pushed towards the periphery due to the presence of a central vacuole

Discovery of Electron Microscope

  • Made it possible to observe and understand the complex structure of cells and their organelles (Knoll and Ruska, 1939)

Precautions for the Experiment

  • Immediately place the onion peel in a water-containing petri-dish to avoid folding and drying
  • Spread the peel uniformly on the slide
  • Drain excess stain
  • Ensure no air bubbles form under the coverslip

Preparing a Temporary Stained Slide of Squamous Epithelial Cells

  • To prepare a temporary stained slide, wash your mouth and scrape a little of the internal lining of your mouth with a clean toothpick or scapula or ice-cream spoon.
  • Place the scraping in a watch glass containing a small quantity of normal saline with the help of a needle.
  • Transfer the material to a glass slide after cleaning.

Staining the Cells

  • Add a drop of methylene blue to the slide and wait for a couple of minutes.
  • Wipe off the extra stain with a dropper or blotting paper.
  • Put a drop of glycerine on the stained material.

Mounting the Slide

  • Place a coverslip on the slide and tap it gently with the blunt end of a needle to spread the cells.
  • Observe the temporary mount under low and high power of a microscope.

Characteristics of Squamous Epithelial Cells

  • The cells are flat and polygonal in shape with a distinct rounded nucleus in the middle.
  • Each cell is bounded by a thin cell membrane.
  • The cytoplasm is lightly stained.

Precautions

  • Avoid scraping the cheek too hard, as it may injure the buccal mucosa.
  • Ensure the scrapped material is spread uniformly on the slide.
  • Drain off excess stain.
  • Prevent air-bubbles from forming under the coverslip.

Significance of the Activity

  • This activity confirms that cells are the basic structural unit of life.
  • It demonstrates that not only human cheek cells but also all organisms are made up of cells.

Preparing a Temporary Stained Slide of Squamous Epithelial Cells

  • To prepare a temporary stained slide, wash your mouth and scrape a little of the internal lining of your mouth with a clean toothpick or scapula or ice-cream spoon.
  • Place the scraping in a watch glass containing a small quantity of normal saline with the help of a needle.
  • Transfer the material to a glass slide after cleaning.

Staining the Cells

  • Add a drop of methylene blue to the slide and wait for a couple of minutes.
  • Wipe off the extra stain with a dropper or blotting paper.
  • Put a drop of glycerine on the stained material.

Mounting the Slide

  • Place a coverslip on the slide and tap it gently with the blunt end of a needle to spread the cells.
  • Observe the temporary mount under low and high power of a microscope.

Characteristics of Squamous Epithelial Cells

  • The cells are flat and polygonal in shape with a distinct rounded nucleus in the middle.
  • Each cell is bounded by a thin cell membrane.
  • The cytoplasm is lightly stained.

Precautions

  • Avoid scraping the cheek too hard, as it may injure the buccal mucosa.
  • Ensure the scrapped material is spread uniformly on the slide.
  • Drain off excess stain.
  • Prevent air-bubbles from forming under the coverslip.

Significance of the Activity

  • This activity confirms that cells are the basic structural unit of life.
  • It demonstrates that not only human cheek cells but also all organisms are made up of cells.

Cell Size

  • Normal size of human cells: 20-30 μm in diameter
  • Largest cell in animals: Ostrich egg, 15 cm in diameter
  • Largest cell in plants: Acetabularia, 6-10 cm in diameter
  • Longest cell in animals: Nerve cell, up to 1 meter in length
  • Longest cell in plants: Hemp fiber
  • Smallest cell: PPLO (Pleuro Pneumoniae Like Organism, also known as Mycoplasma), 0.1-0.5 μm in diameter
  • Largest human cell: Female ovum, 0.01 mm in diameter
  • Smallest human cell: Red blood cell, 7.5 μm in diameter

Cell Shape

  • Shape of cell depends on its specific function
  • Examples of cell shapes:
    • Elongated and branched: Nerve cell
    • Discoidal/saucer: Red blood cell
    • Spindle: Muscle cell
    • Spherical: Eggs
    • Branched: Pigment cell of the skin
    • Slipper-shaped: Paramecium
    • Cuboidal: Germ cells of gonads
    • Polygonal: Liver cells

Cell Organelles

  • All cells have the same organelles, regardless of function and location in an organism

Cell Size

  • Normal size of human cells: 20-30 μm in diameter
  • Largest cell in animals: Ostrich egg, 15 cm in diameter
  • Largest cell in plants: Acetabularia, 6-10 cm in diameter
  • Longest cell in animals: Nerve cell, up to 1 meter in length
  • Longest cell in plants: Hemp fiber
  • Smallest cell: PPLO (Pleuro Pneumoniae Like Organism, also known as Mycoplasma), 0.1-0.5 μm in diameter
  • Largest human cell: Female ovum, 0.01 mm in diameter
  • Smallest human cell: Red blood cell, 7.5 μm in diameter

Cell Shape

  • Shape of cell depends on its specific function
  • Examples of cell shapes:
    • Elongated and branched: Nerve cell
    • Discoidal/saucer: Red blood cell
    • Spindle: Muscle cell
    • Spherical: Eggs
    • Branched: Pigment cell of the skin
    • Slipper-shaped: Paramecium
    • Cuboidal: Germ cells of gonads
    • Polygonal: Liver cells

Cell Organelles

  • All cells have the same organelles, regardless of function and location in an organism

Cell Shapes and Functions

  • Cells exhibit a great variation in shape, including spherical, oval, rounded, elongated, cuboidal, cylindrical, tubular, discoidal, and irregular.
  • The shape of cells is often related to the different functions they perform.

Examples of Cell Shapes and Functions

  • Human white blood cells are amoeboid, allowing them to squeeze out through capillary walls.
  • Red blood cells are circular and biconcave, enabling them to move easily through small spaces and transport oxygen.
  • Nerve cells are long, facilitating the conduction of impulses from distant parts of the body to the brain and vice versa.
  • Muscle cells are long and contractile, helping in the movement of bones.
  • Xylem vessels are long and elongated, aiding in the conduction of water and minerals.
  • Guard cells in plant leaves are kidney-shaped, allowing them to open and close stomata to facilitate gas exchange.

Cell Size and Number

  • The size of an organism is dependent on the number of cells, not on the size of the cells.
  • Unicellular organisms, such as bacteria, Amoeba, Paramecium, and Chlamydomonas, are composed of a single cell that performs all life processes, including obtaining food, respiration, excretion, growth, and reproduction.
  • Multicellular organisms, on the other hand, are composed of multiple cells that work together to perform various functions.

Cell Shapes and Functions

  • Cells exhibit a great variation in shape, including spherical, oval, rounded, elongated, cuboidal, cylindrical, tubular, discoidal, and irregular.
  • The shape of cells is often related to the different functions they perform.

Examples of Cell Shapes and Functions

  • Human white blood cells are amoeboid, allowing them to squeeze out through capillary walls.
  • Red blood cells are circular and biconcave, enabling them to move easily through small spaces and transport oxygen.
  • Nerve cells are long, facilitating the conduction of impulses from distant parts of the body to the brain and vice versa.
  • Muscle cells are long and contractile, helping in the movement of bones.
  • Xylem vessels are long and elongated, aiding in the conduction of water and minerals.
  • Guard cells in plant leaves are kidney-shaped, allowing them to open and close stomata to facilitate gas exchange.

Cell Size and Number

  • The size of an organism is dependent on the number of cells, not on the size of the cells.
  • Unicellular organisms, such as bacteria, Amoeba, Paramecium, and Chlamydomonas, are composed of a single cell that performs all life processes, including obtaining food, respiration, excretion, growth, and reproduction.
  • Multicellular organisms, on the other hand, are composed of multiple cells that work together to perform various functions.

Characteristics of Multicellular Organisms

  • Multicellular organisms are made up of more than one cell, e.g. Fungi (except yeast), plants, and animals.
  • Cells in multicellular organisms have similar basic structure and undertake similar basic functions.

Division of Labour

  • In multicellular organisms, cells are specialized to perform different functions of the body due to division of labour.
  • In unicellular organisms, a single cell performs all activities.

Discovery of Cells

  • Robert Hooke discovered small box-like structures in cork and named them "cellula" (later abbreviated to "cell") in 1665.
  • His work was published in the book "Micrographia".

Cell: The Unit of Life

  • A living organism is made up of one or more cells.
  • The cell is the structural and functional unit of life.
  • All life functions of an organism reside in its cells.

Cell Specialization

  • Cells can become specialized to perform specific functions, e.g. contraction in muscle cells or impulse transmission in nerve cells.
  • Therefore, cells are functional units of life.

Basic Structure of a Cell

  • Plant and animal cells have three main parts:
    • Cell membrane
    • Cytoplasm
    • Nucleus

Characteristics of Multicellular Organisms

  • Multicellular organisms are made up of more than one cell, e.g. Fungi (except yeast), plants, and animals.
  • Cells in multicellular organisms have similar basic structure and undertake similar basic functions.

Division of Labour

  • In multicellular organisms, cells are specialized to perform different functions of the body due to division of labour.
  • In unicellular organisms, a single cell performs all activities.

Discovery of Cells

  • Robert Hooke discovered small box-like structures in cork and named them "cellula" (later abbreviated to "cell") in 1665.
  • His work was published in the book "Micrographia".

Cell: The Unit of Life

  • A living organism is made up of one or more cells.
  • The cell is the structural and functional unit of life.
  • All life functions of an organism reside in its cells.

Cell Specialization

  • Cells can become specialized to perform specific functions, e.g. contraction in muscle cells or impulse transmission in nerve cells.
  • Therefore, cells are functional units of life.

Basic Structure of a Cell

  • Plant and animal cells have three main parts:
    • Cell membrane
    • Cytoplasm
    • Nucleus

Protoplasm

  • Protoplasm is the living substance of a cell
  • It is divided into two parts: nucleoplasm (found in the nucleus) and cytoplasm (found outside the nucleus)

Cell Organelles

  • Cell organelles are structures found in the cytoplasm of a cell
  • Each organelle performs a specific function

Plasma Membrane

  • Also known as cell membrane
  • Found in all living cells, including prokaryotic and eukaryotic cells
  • Semi-permeable or selectively permeable barrier to the outside environment
  • Allows nutrients and essential elements to enter the cell and waste materials to leave
  • Permeable to small molecules such as oxygen, carbon dioxide, and water
  • Regulates the passage of larger molecules such as amino acids and sugars
  • Flexible and composed of lipids and proteins
  • Performs the following functions:
    • Protects the internal components of the cell
    • Provides shape to the cell
    • Allows materials to enter and leave the cell through tiny holes

Cell Wall

  • Found in plant cells, bacterial cells, and fungal cells
  • Non-living and freely permeable
  • Provides protection against variations in temperature, high wind speed, and atmospheric moisture
  • Composed of cellulose in plant cells
  • Functions:
    • Gives a definite shape to the cell
    • Provides strength and rigidity to the cell

Protoplasm

  • Protoplasm is the living substance of a cell
  • It is divided into two parts: nucleoplasm (found in the nucleus) and cytoplasm (found outside the nucleus)

Cell Organelles

  • Cell organelles are structures found in the cytoplasm of a cell
  • Each organelle performs a specific function

Plasma Membrane

  • Also known as cell membrane
  • Found in all living cells, including prokaryotic and eukaryotic cells
  • Semi-permeable or selectively permeable barrier to the outside environment
  • Allows nutrients and essential elements to enter the cell and waste materials to leave
  • Permeable to small molecules such as oxygen, carbon dioxide, and water
  • Regulates the passage of larger molecules such as amino acids and sugars
  • Flexible and composed of lipids and proteins
  • Performs the following functions:
    • Protects the internal components of the cell
    • Provides shape to the cell
    • Allows materials to enter and leave the cell through tiny holes

Cell Wall

  • Found in plant cells, bacterial cells, and fungal cells
  • Non-living and freely permeable
  • Provides protection against variations in temperature, high wind speed, and atmospheric moisture
  • Composed of cellulose in plant cells
  • Functions:
    • Gives a definite shape to the cell
    • Provides strength and rigidity to the cell

Cell Wall vs Cell Membrane

  • Cell wall is the outer thick, protective layer of the cell found only in bacterial and plant cells, non-living and freely permeable.
  • Cell membrane is the outer covering of the protoplasm found in plant and animal cells, living and selectively permeable.

Cytoplasm

  • Cytoplasm is the fluid content/protoplasmic mass of the cell inner to plasma membrane, excluding the nucleus.
  • Composed of matrix, organelles, and non-living inclusions like vacuoles and granules.

Nucleus

  • Most important part of the living cell, usually spherical or oval in shape.
  • Controls all vital functions of the cell.
  • Four components: Nuclear Membrane, Nucleoplasm, Nucleolus, and Chromatin material.

Nuclear Components

  • Nuclear Membrane: surrounds the nucleus, separates it from cytoplasm, and is permeable.
  • Nucleoplasm: part of protoplasm enclosed by nuclear membrane, contains chromatin threads and nucleolus.
  • Nucleolus: spherical body in the nucleus, rich in proteins and RNA, produces ribosomes.
  • Chromatin material: darkly stained network of long and fine threads, forms a network called chromatin reticulum.

Cell Classification

  • Prokaryotes: organisms whose cells lack a nuclear membrane, genetic material lies freely in the form of nucleoid (e.g. Bacteria, blue green algae).
  • Eukaryotes: organisms whose cells have a well-organized nucleus with a nuclear membrane (e.g. all plant and animal cells).

Cell Wall vs Cell Membrane

  • Cell wall is the outer thick, protective layer of the cell found only in bacterial and plant cells, non-living and freely permeable.
  • Cell membrane is the outer covering of the protoplasm found in plant and animal cells, living and selectively permeable.

Cytoplasm

  • Cytoplasm is the fluid content/protoplasmic mass of the cell inner to plasma membrane, excluding the nucleus.
  • Composed of matrix, organelles, and non-living inclusions like vacuoles and granules.

Nucleus

  • Most important part of the living cell, usually spherical or oval in shape.
  • Controls all vital functions of the cell.
  • Four components: Nuclear Membrane, Nucleoplasm, Nucleolus, and Chromatin material.

Nuclear Components

  • Nuclear Membrane: surrounds the nucleus, separates it from cytoplasm, and is permeable.
  • Nucleoplasm: part of protoplasm enclosed by nuclear membrane, contains chromatin threads and nucleolus.
  • Nucleolus: spherical body in the nucleus, rich in proteins and RNA, produces ribosomes.
  • Chromatin material: darkly stained network of long and fine threads, forms a network called chromatin reticulum.

Cell Classification

  • Prokaryotes: organisms whose cells lack a nuclear membrane, genetic material lies freely in the form of nucleoid (e.g. Bacteria, blue green algae).
  • Eukaryotes: organisms whose cells have a well-organized nucleus with a nuclear membrane (e.g. all plant and animal cells).

Cell Wall vs Cell Membrane

  • Cell wall is the outer thick, protective layer of the cell found only in bacterial and plant cells, non-living and freely permeable.
  • Cell membrane is the outer covering of the protoplasm found in plant and animal cells, living and selectively permeable.

Cytoplasm

  • Cytoplasm is the fluid content/protoplasmic mass of the cell inner to plasma membrane, excluding the nucleus.
  • Composed of matrix, organelles, and non-living inclusions like vacuoles and granules.

Nucleus

  • Most important part of the living cell, usually spherical or oval in shape.
  • Controls all vital functions of the cell.
  • Four components: Nuclear Membrane, Nucleoplasm, Nucleolus, and Chromatin material.

Nuclear Components

  • Nuclear Membrane: surrounds the nucleus, separates it from cytoplasm, and is permeable.
  • Nucleoplasm: part of protoplasm enclosed by nuclear membrane, contains chromatin threads and nucleolus.
  • Nucleolus: spherical body in the nucleus, rich in proteins and RNA, produces ribosomes.
  • Chromatin material: darkly stained network of long and fine threads, forms a network called chromatin reticulum.

Cell Classification

  • Prokaryotes: organisms whose cells lack a nuclear membrane, genetic material lies freely in the form of nucleoid (e.g. Bacteria, blue green algae).
  • Eukaryotes: organisms whose cells have a well-organized nucleus with a nuclear membrane (e.g. all plant and animal cells).

Cell Wall vs Cell Membrane

  • Cell wall is the outer thick, protective layer of the cell found only in bacterial and plant cells, non-living and freely permeable.
  • Cell membrane is the outer covering of the protoplasm found in plant and animal cells, living and selectively permeable.

Cytoplasm

  • Cytoplasm is the fluid content/protoplasmic mass of the cell inner to plasma membrane, excluding the nucleus.
  • Composed of matrix, organelles, and non-living inclusions like vacuoles and granules.

Nucleus

  • Most important part of the living cell, usually spherical or oval in shape.
  • Controls all vital functions of the cell.
  • Four components: Nuclear Membrane, Nucleoplasm, Nucleolus, and Chromatin material.

Nuclear Components

  • Nuclear Membrane: surrounds the nucleus, separates it from cytoplasm, and is permeable.
  • Nucleoplasm: part of protoplasm enclosed by nuclear membrane, contains chromatin threads and nucleolus.
  • Nucleolus: spherical body in the nucleus, rich in proteins and RNA, produces ribosomes.
  • Chromatin material: darkly stained network of long and fine threads, forms a network called chromatin reticulum.

Cell Classification

  • Prokaryotes: organisms whose cells lack a nuclear membrane, genetic material lies freely in the form of nucleoid (e.g. Bacteria, blue green algae).
  • Eukaryotes: organisms whose cells have a well-organized nucleus with a nuclear membrane (e.g. all plant and animal cells).

Cell Structure and Function

  • Sieve tube cells in plants and mature mammalian red blood cells lack a nucleus.
  • Nucleopores facilitate exchange of substances between nucleoplasm and cytoplasm.
  • Chromosomes are composed of DNA and proteins.
  • DNA carries genetic information passed on to the next generation.
  • Functional segments of DNA are called genes.

Prokaryotes and Eukaryotes

  • Prokaryotes are cells without a nucleus, whereas eukaryotes have a nucleus.

Cell Wall

  • Cell wall is a structural component of cells.

Plastids

  • Plastids are major organelles found in plant and green alga cells.
  • They are responsible for manufacturing and storing important chemical compounds.
  • Plastids contain pigments used in photosynthesis, determining the cell's color.
  • They are double membrane-bound organelles.
  • Types of plastids include:
    • Chromoplasts: red, yellow, or orange in color, found in petals and fruits, involved in pigment synthesis and storage.
    • Leucoplasts: colorless or white, found in plant cells not exposed to light, such as roots and seeds, store food in the form of starch, proteins, and fats.
    • Chloroplasts: directly involved in photosynthesis, green in color due to chlorophyll, probably the most important type of plastid.

Cell Structure and Function

  • Sieve tube cells in plants and mature mammalian red blood cells lack a nucleus.
  • Nucleopores facilitate exchange of substances between nucleoplasm and cytoplasm.
  • Chromosomes are composed of DNA and proteins.
  • DNA carries genetic information passed on to the next generation.
  • Functional segments of DNA are called genes.

Prokaryotes and Eukaryotes

  • Prokaryotes are cells without a nucleus, whereas eukaryotes have a nucleus.

Cell Wall

  • Cell wall is a structural component of cells.

Plastids

  • Plastids are major organelles found in plant and green alga cells.
  • They are responsible for manufacturing and storing important chemical compounds.
  • Plastids contain pigments used in photosynthesis, determining the cell's color.
  • They are double membrane-bound organelles.
  • Types of plastids include:
    • Chromoplasts: red, yellow, or orange in color, found in petals and fruits, involved in pigment synthesis and storage.
    • Leucoplasts: colorless or white, found in plant cells not exposed to light, such as roots and seeds, store food in the form of starch, proteins, and fats.
    • Chloroplasts: directly involved in photosynthesis, green in color due to chlorophyll, probably the most important type of plastid.

Cell Structure and Function

  • Sieve tube cells in plants and mature mammalian red blood cells lack a nucleus.
  • Nucleopores facilitate exchange of substances between nucleoplasm and cytoplasm.
  • Chromosomes are composed of DNA and proteins.
  • DNA carries genetic information passed on to the next generation.
  • Functional segments of DNA are called genes.

Prokaryotes and Eukaryotes

  • Prokaryotes are cells without a nucleus, whereas eukaryotes have a nucleus.

Cell Wall

  • Cell wall is a structural component of cells.

Plastids

  • Plastids are major organelles found in plant and green alga cells.
  • They are responsible for manufacturing and storing important chemical compounds.
  • Plastids contain pigments used in photosynthesis, determining the cell's color.
  • They are double membrane-bound organelles.
  • Types of plastids include:
    • Chromoplasts: red, yellow, or orange in color, found in petals and fruits, involved in pigment synthesis and storage.
    • Leucoplasts: colorless or white, found in plant cells not exposed to light, such as roots and seeds, store food in the form of starch, proteins, and fats.
    • Chloroplasts: directly involved in photosynthesis, green in color due to chlorophyll, probably the most important type of plastid.

Structure of Chloroplast

  • Chloroplasts are usually disc-shaped and surrounded by a double membrane.
  • Inside the inner membrane, there is a watery protein-rich ground substance called stroma.
  • Stroma contains various photosynthetic enzymes and starch grains.
  • Thylakoids, which are membrane-bound vesicles, are present in the stroma in a three-dimensional arrangement.
  • Thylakoids are stacked in grana and contain the photosynthetic pigment chlorophyll.
  • Grana are interconnected by tubular membranes called intergranal frets or lamellae.

Cell Membrane

  • The cell membrane is a semipermeable membrane that permits the entry of gases through diffusion.
  • Ions, sugar, amino acids, etc. pass through the plasma membrane by an active process.
  • The plasma membrane is selectively permeable, being impermeable to certain materials.

Prokaryotes and Eukaryotes

  • Prokaryotes are organisms whose cells lack a nuclear membrane, and the genetic material lies freely in the form of nucleoid.
  • Examples of prokaryotes include bacteria and blue-green algae.
  • Eukaryotes are organisms whose cells have a well-organized nucleus with a nuclear membrane.
  • Examples of eukaryotes include all plant and animal cells.

Cell Wall

  • The cell wall is a non-living, freely permeable outer layer in plant cells that provides protection.
  • It is an additional layer surrounding the cell membrane.

Ribosomes

  • Ribosomes are the protein builders or protein synthesizers of the cell.
  • They are responsible for synthesizing proteins that might be used as enzymes or for other cell functions.
  • Ribosomes consist of two subunits: a large subunit and a small subunit.
  • They can be either free or bound (attached).
  • Ribosomes are also known as the "Engine of the cell".

Vacuoles

  • Vacuoles are membrane-bound, non-cytoplasmic sacs that contain non-living liquid or solid contents.
  • They are common in both plant and animal cells.
  • In animal and young plant cells, sap vacuoles are small.
  • In mature plant cells, there is a large central vacuole occupying 50-90% of cell volume.
  • The covering membrane of the sap vacuole is called tonoplast.
  • The fluid content of the vacuole is called cell sap.
  • Sap vacuoles store salts, sugar, amino acid, organic acids, and some proteins.
  • They also act as a dump for waste products in plant cells.
  • Sap vacuoles help in maintaining turgidity and rigidity of the cell and are required for osmotic absorption of water.

Structure of Chloroplast

  • Chloroplasts are usually disc-shaped and surrounded by a double membrane.
  • Inside the inner membrane, there is a watery protein-rich ground substance called stroma.
  • Stroma contains various photosynthetic enzymes and starch grains.
  • Thylakoids, which are membrane-bound vesicles, are present in the stroma in a three-dimensional arrangement.
  • Thylakoids are stacked in grana and contain the photosynthetic pigment chlorophyll.
  • Grana are interconnected by tubular membranes called intergranal frets or lamellae.

Cell Membrane

  • The cell membrane is a semipermeable membrane that permits the entry of gases through diffusion.
  • Ions, sugar, amino acids, etc. pass through the plasma membrane by an active process.
  • The plasma membrane is selectively permeable, being impermeable to certain materials.

Prokaryotes and Eukaryotes

  • Prokaryotes are organisms whose cells lack a nuclear membrane, and the genetic material lies freely in the form of nucleoid.
  • Examples of prokaryotes include bacteria and blue-green algae.
  • Eukaryotes are organisms whose cells have a well-organized nucleus with a nuclear membrane.
  • Examples of eukaryotes include all plant and animal cells.

Cell Wall

  • The cell wall is a non-living, freely permeable outer layer in plant cells that provides protection.
  • It is an additional layer surrounding the cell membrane.

Ribosomes

  • Ribosomes are the protein builders or protein synthesizers of the cell.
  • They are responsible for synthesizing proteins that might be used as enzymes or for other cell functions.
  • Ribosomes consist of two subunits: a large subunit and a small subunit.
  • They can be either free or bound (attached).
  • Ribosomes are also known as the "Engine of the cell".

Vacuoles

  • Vacuoles are membrane-bound, non-cytoplasmic sacs that contain non-living liquid or solid contents.
  • They are common in both plant and animal cells.
  • In animal and young plant cells, sap vacuoles are small.
  • In mature plant cells, there is a large central vacuole occupying 50-90% of cell volume.
  • The covering membrane of the sap vacuole is called tonoplast.
  • The fluid content of the vacuole is called cell sap.
  • Sap vacuoles store salts, sugar, amino acid, organic acids, and some proteins.
  • They also act as a dump for waste products in plant cells.
  • Sap vacuoles help in maintaining turgidity and rigidity of the cell and are required for osmotic absorption of water.

Cell Division and Specialization

  • Cell division is the process by which a cell divides to form two new cells.
  • Importance of cell division:
    • For growth: necessary for multicellular organisms to grow from a single cell.
    • For replacement of old cells: helps replace old and worn-out cells.
    • For reproduction: essential for reproduction and birth of new individuals.
    • For repair: replaces damaged or worn-out cells with new ones.

Cell Organelles and Their Functions

  • Contractile vacuole: involved in osmoregulation and excretion in unicellular freshwater organisms.
  • Chloroplast: not mentioned in this context.
  • Nucleus: not mentioned in this context.
  • Leucoplasts: not mentioned in this context.
  • Ribosomes: involved in protein synthesis, found in free and bound forms.
  • Mitochondria: not mentioned in this context, but has a special function within the cell.
  • Cell specialization: similar to 'division of labour' within an organism, where cells carry out specific functions.
  • Organelle specialization: similar to 'division of labour' within a cell, where organelles have specific functions.

Cell Division and Specialization

  • Cell division is the process by which a cell divides to form two new cells.
  • Importance of cell division:
    • For growth: necessary for multicellular organisms to grow from a single cell.
    • For replacement of old cells: helps replace old and worn-out cells.
    • For reproduction: essential for reproduction and birth of new individuals.
    • For repair: replaces damaged or worn-out cells with new ones.

Cell Organelles and Their Functions

  • Contractile vacuole: involved in osmoregulation and excretion in unicellular freshwater organisms.
  • Chloroplast: not mentioned in this context.
  • Nucleus: not mentioned in this context.
  • Leucoplasts: not mentioned in this context.
  • Ribosomes: involved in protein synthesis, found in free and bound forms.
  • Mitochondria: not mentioned in this context, but has a special function within the cell.
  • Cell specialization: similar to 'division of labour' within an organism, where cells carry out specific functions.
  • Organelle specialization: similar to 'division of labour' within a cell, where organelles have specific functions.

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Learn about the basic structure and function of cells, the smallest units of life. Discover how cells divide, differentiate, and form tissues and organs. Explore the history of cell discovery and its significance in biology.

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