This document describes the structures found within plant cells. It discusses the two main types of cells - prokaryotes and eukaryotes. Eukaryotic plant cells contain organelles such as the cell wall, chloroplasts, mitochondria, vacuoles, and a nucleus. The nucleus contains the cell's genetic material. Other structures in the plant cell include the endoplasmic reticulum, Golgi bodies, lysosomes, peroxisomes, microtubules, and ribosomes. Plastids like chloroplasts, leucoplasts, and chromoplasts are also described. The three main types of cells in plants are parenchyma, collenchyma, and sclerenchyma cells.
Cells are the basic units of life and come in two main types - prokaryotic and eukaryotic. Prokaryotic cells were the first to evolve and are much smaller, containing a cell membrane, cytoplasm, genetic material, and some organelles. Eukaryotic cells are larger and more complex, containing a nucleus surrounded by a nuclear envelope and specialized organelles that carry out different functions. The organelles work together through the transport of vesicles to synthesize proteins and carry out other processes necessary for cellular function.
Ultra structure of Plant Cell by Salman Saeed Lecturer Botany UCMS KhanewalSalman Saeed
This document provides an overview of a cell biology, genetics, and evolution course taught by Salman Saeed at the University College of Management & Sciences in Khanewal, Pakistan. It includes definitions and descriptions of key cellular organelles such as the cell membrane, nucleus, mitochondria, chloroplasts, endoplasmic reticulum, Golgi apparatus, lysosomes, ribosomes, cytoskeleton, and vacuoles. Their functions in processes like cellular respiration, protein synthesis, transport, and waste disposal are discussed at a basic level. Plant cell walls and their chemical composition are also reviewed.
This document provides information on cell structure and organization. It describes typical animal and plant cell structures as seen under light and electron microscopes. Key structures discussed include the nucleus, endoplasmic reticulum, Golgi apparatus, mitochondria, chloroplasts, cell wall, and vacuoles. It also covers tissues, organs, organ systems, and the differences between prokaryotic and eukaryotic cells.
Cell Structure and Function outlines key concepts in cell biology. It discusses that cells are the basic unit of life and were first observed by Robert Hooke in the 1600s. Theodor Schwann and Matthias Schleiden established cell theory in 1839, stating that all living things are made of cells, and Rudolf Virchow later added that all cells come from preexisting cells. All cells have a plasma membrane, cytoplasm, and organelles like the nucleus. Prokaryotic cells lack organelles while eukaryotic cells have organelles like the nucleus. The document then describes various organelle structures and functions like the endoplasmic reticulum, Golgi apparatus, mitochondria, and chloroplasts. It also covers
The document provides an overview of cell structure and function. It discusses the key discoveries and principles of cell theory. The main components of cells are then described, including the plasma membrane, cytoplasm, cytoskeleton, organelles, and cell walls. Specific organelles like the nucleus, mitochondria, chloroplasts, and Golgi apparatus are explained. The processes of passive transport, active transport, endocytosis, and exocytosis are also summarized.
This document describes the key components and steps of gel electrophoresis. It explains that gel electrophoresis uses an electric field to separate biomolecules like proteins, carbohydrates, and nucleic acids based on their size and charge. The document outlines the main parts of the gel electrophoresis process, including preparing the gel and samples, running the gel, and staining the gel to visualize the separated biomolecules.
1. Before microscopes, people believed diseases were caused by curses or spirits and had no idea cells existed. Scientists began studying cells using microscopes in the 1600s.
2. Robert Hooke used an early microscope to observe "cells" in plant material in 1665, helping establish the cell theory that organisms are made of basic unit(s) called cells.
3. The development of electron microscopes in the 1930s-1940s allowed scientists to view cell structures at much higher magnifications, revealing internal structures like organelles that carry out key functions.
This document summarizes various cell structures and their functions. It discusses ribosomes, which synthesize proteins, and polyribosomes, the components of which include DNA, mRNA, tRNA and rRNA. It describes the endoplasmic reticulum, where proteins are synthesized and modified, and the Golgi apparatus, where proteins and carbohydrates are further processed and sorted. Lysosomes aid digestion, while peroxisomes contain oxidative enzymes and aid in protein degradation. Mitochondria perform oxidative phosphorylation and lipid synthesis. The cytoskeleton, comprising actin filaments, intermediate filaments and microtubules, maintains cell shape and enables intracellular movement.
Cells are the basic units of life and come in two main types - prokaryotic and eukaryotic. Prokaryotic cells were the first to evolve and are much smaller, containing a cell membrane, cytoplasm, genetic material, and some organelles. Eukaryotic cells are larger and more complex, containing a nucleus surrounded by a nuclear envelope and specialized organelles that carry out different functions. The organelles work together through the transport of vesicles to synthesize proteins and carry out other processes necessary for cellular function.
Ultra structure of Plant Cell by Salman Saeed Lecturer Botany UCMS KhanewalSalman Saeed
This document provides an overview of a cell biology, genetics, and evolution course taught by Salman Saeed at the University College of Management & Sciences in Khanewal, Pakistan. It includes definitions and descriptions of key cellular organelles such as the cell membrane, nucleus, mitochondria, chloroplasts, endoplasmic reticulum, Golgi apparatus, lysosomes, ribosomes, cytoskeleton, and vacuoles. Their functions in processes like cellular respiration, protein synthesis, transport, and waste disposal are discussed at a basic level. Plant cell walls and their chemical composition are also reviewed.
This document provides information on cell structure and organization. It describes typical animal and plant cell structures as seen under light and electron microscopes. Key structures discussed include the nucleus, endoplasmic reticulum, Golgi apparatus, mitochondria, chloroplasts, cell wall, and vacuoles. It also covers tissues, organs, organ systems, and the differences between prokaryotic and eukaryotic cells.
Cell Structure and Function outlines key concepts in cell biology. It discusses that cells are the basic unit of life and were first observed by Robert Hooke in the 1600s. Theodor Schwann and Matthias Schleiden established cell theory in 1839, stating that all living things are made of cells, and Rudolf Virchow later added that all cells come from preexisting cells. All cells have a plasma membrane, cytoplasm, and organelles like the nucleus. Prokaryotic cells lack organelles while eukaryotic cells have organelles like the nucleus. The document then describes various organelle structures and functions like the endoplasmic reticulum, Golgi apparatus, mitochondria, and chloroplasts. It also covers
The document provides an overview of cell structure and function. It discusses the key discoveries and principles of cell theory. The main components of cells are then described, including the plasma membrane, cytoplasm, cytoskeleton, organelles, and cell walls. Specific organelles like the nucleus, mitochondria, chloroplasts, and Golgi apparatus are explained. The processes of passive transport, active transport, endocytosis, and exocytosis are also summarized.
This document describes the key components and steps of gel electrophoresis. It explains that gel electrophoresis uses an electric field to separate biomolecules like proteins, carbohydrates, and nucleic acids based on their size and charge. The document outlines the main parts of the gel electrophoresis process, including preparing the gel and samples, running the gel, and staining the gel to visualize the separated biomolecules.
1. Before microscopes, people believed diseases were caused by curses or spirits and had no idea cells existed. Scientists began studying cells using microscopes in the 1600s.
2. Robert Hooke used an early microscope to observe "cells" in plant material in 1665, helping establish the cell theory that organisms are made of basic unit(s) called cells.
3. The development of electron microscopes in the 1930s-1940s allowed scientists to view cell structures at much higher magnifications, revealing internal structures like organelles that carry out key functions.
This document summarizes various cell structures and their functions. It discusses ribosomes, which synthesize proteins, and polyribosomes, the components of which include DNA, mRNA, tRNA and rRNA. It describes the endoplasmic reticulum, where proteins are synthesized and modified, and the Golgi apparatus, where proteins and carbohydrates are further processed and sorted. Lysosomes aid digestion, while peroxisomes contain oxidative enzymes and aid in protein degradation. Mitochondria perform oxidative phosphorylation and lipid synthesis. The cytoskeleton, comprising actin filaments, intermediate filaments and microtubules, maintains cell shape and enables intracellular movement.
- Cells are the smallest living units that make up all living things. All cells come from pre-existing cells.
- Cells can be either prokaryotic or eukaryotic. Eukaryotic cells contain a nucleus and membrane-bound organelles, while prokaryotic cells do not have a nucleus or membrane-bound organelles.
- Organelles such as the nucleus, mitochondria, chloroplasts, endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles allow cells to carry out specialized functions and processes like respiration, photosynthesis, protein transport, and waste removal.
- Cells are the smallest living units that make up all living things. All cells come from pre-existing cells.
- Cells can be either prokaryotic or eukaryotic. Eukaryotic cells contain membrane-bound organelles and a nucleus, while prokaryotic cells do not.
- Organelles such as the nucleus, mitochondria, chloroplasts, endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles allow cells to carry out specialized functions and processes like respiration, photosynthesis, protein transport, and waste removal.
- Molecules can move across the cell membrane through passive transport mechanisms like diffusion, osmosis, and facilitated diffusion which do not require
The document discusses the parts of an animal cell and their functions. It aims to teach students to identify and draw the major organelles of an animal cell, including the nucleus, nucleolus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, cytoskeleton, cell membrane, ribosomes, vesicles, and cytosol. Understanding the structure and role of each organelle is important for studying biology at a cellular level.
The cell wall, endomembrane system, and vacuoles are important organelles in plant and fungal cells. The cell wall provides structure, protection, and allows for cell-to-cell interaction. It consists of cellulose, hemicellulose, and pectins in plants. The endomembrane system, including the endoplasmic reticulum, Golgi apparatus, lysosomes coordinates functions like protein transport and modification. The endoplasmic reticulum synthesizes lipids and proteins. The Golgi apparatus packages and modifies proteins and lipids. Lysosomes contain enzymes for digestion. Vacuoles store waste and regulate the cell's internal environment.
This document provides an overview of cell structure and function. It begins by defining key terms like cell membrane, cytoplasm, organelles, and nucleus. It then describes the characteristics of prokaryotic and eukaryotic cells, including their differences. The majority of the document details the structures and functions of various organelles found in eukaryotic cells, such as the nucleus, endoplasmic reticulum, Golgi apparatus, mitochondria, chloroplasts, and vacuoles. It also explains cellular processes like transport across the cell membrane, photosynthesis, and protein synthesis.
General Introduction of Plant Cell & its Organelles by Salman Saeed Lecturer ...Salman Saeed
Cell Biology for Master,s Level Students
Best notes for Biology/Botany/Zoology/Chemistry/Molecular Biology/Biotechnology and Biochemistry Students
Genetics
UCMS Khanewal
The document summarizes key aspects of prokaryotic and eukaryotic cell structure. It describes the three layered cell envelope of most prokaryotic cells, consisting of an outer glycocalyx, middle cell wall, and inner plasma membrane. It also discusses how bacteria can be classified as Gram-positive or Gram-negative based on differences in their cell envelopes and staining. The document then covers additional structures like flagella, pili, and inclusion bodies in prokaryotes, as well as organelles and cytoskeletal elements in eukaryotic cells. It concludes by outlining the fluid mosaic model of the cell membrane and different transport mechanisms like diffusion, osmosis, facilitated transport, and active transport
独中高一生物 2.2.2 nucleus UEC Senior 1 Biology Yee Sing Ong
The document provides information about the structure and function of the nucleus in eukaryotic cells. It discusses that:
1) Most eukaryotic cells contain a single nucleus, though some contain multiple nuclei like muscle and liver cells. The nuclei contain genetic material and can be seen under light microscopes after staining.
2) The nucleus functions to compartmentalize the cell, store and replicate genetic material, and control gene expression and cell metabolism. Cells without a nucleus cannot replicate, grow, or survive for long.
3) The main nuclear structures are the nuclear envelope, nuclear pores, nucleolus, and chromatin. The nuclear envelope separates the nucleus from the cytoplasm, and nuclear pores allow transport between them
The document discusses the cellular level of organization. It defines the cell as the basic structural and functional unit of life. It outlines the cell theory and describes the main components of prokaryotic and eukaryotic cells. The key components of cells discussed include the cell membrane, cytoplasm, and nucleus. The cell membrane is selectively permeable and regulates what passes in and out of the cell. The cytoplasm contains organelles and cytosol. The nucleus contains genetic material and directs the cell's activities.
The document summarizes cell theory and the key discoveries leading to its development. It describes the three main tenets of cell theory proposed by Schleiden, Schwann, and Virchow: 1) all organisms are composed of one or more cells, 2) the cell is the basic unit of life, and 3) all cells come from preexisting cells. It also discusses techniques like cell fractionation and chromatography used to isolate and study cellular components like organelles and proteins.
The plasma membrane acts as a gatekeeper that regulates what enters and exits the cell. It uses both passive and active transport. Passive transport relies on diffusion and moves substances along concentration gradients, while active transport requires energy and can move substances against concentration gradients using mechanisms like the sodium-potassium pump. The plasma membrane is a lipid bilayer with embedded proteins that gives cells structure and allows for selective permeability and transport of molecules in and out of the cell.
Structure and function of cell membraneBlancoScience
The cell membrane is made of a phospholipid bilayer that is selectively permeable. It controls what enters and leaves the cell. The fluid mosaic model describes the cell membrane as being made up of phospholipids, proteins, and cholesterol that move fluidly within the bilayer. The membrane contains transport proteins that allow substances to pass through, including ion channels, carrier proteins, receptor proteins, and enzymes. Carrier proteins can facilitate diffusion or active transport of molecules in or out of the cell.
BIOLOGY FORM 4 CHAPTER 3 - MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANENirmala Josephine
The document discusses the movement of substances across cell membranes. It begins by outlining the key topics and learning outcomes, which include explaining passive transport mechanisms like diffusion and osmosis. Diffusion is defined as the passive movement of substances from high to low concentration down a gradient. Facilitated diffusion also occurs passively with the help of channel and carrier proteins. Osmosis is specifically the diffusion of water across membranes to equalize its concentration. The document then details these processes and provides examples to illustrate passive transport in organisms.
The cell membrane is composed of a phospholipid bilayer with embedded proteins. It follows the fluid mosaic model, with phospholipids able to freely move and change places. Membrane proteins come in two types - integral proteins that insert into the membrane and peripheral proteins that attach to surfaces. The membrane controls movement of materials into and out of the cell through passive transport mechanisms like diffusion and facilitated diffusion, as well as active transport powered by protein pumps. It maintains an electrical potential through selective ion transport that powers cellular signaling.
This document provides an introduction to cell structure and function. It defines what cells are and how they were first discovered using microscopes in the 17th century. The three main points of the cell theory are outlined. Cell diversity is discussed in terms of size, shape, and internal organization. The main organelles of animal and plant cells are defined, including their locations and functions. The key differences between plant and animal cells are that plant cells contain cell walls, vacuoles, and plastids.
Eukaryotic and prokaryotic cells differ in their nuclear structure and cell division processes. Eukaryotic cells have a membrane-bound nucleus containing chromosomes and a nucleolus, while prokaryotic cells lack a membrane-bound nucleus and nucleolus. Eukaryotic cells divide their nucleus through mitosis and may undergo meiosis, whereas prokaryotic cells usually divide their nucleoid through binary fission without mitosis or meiosis.
Here are the main parts of the cell labeled:
1. Cell membrane - The outer boundary of the cell that regulates what enters and exits.
2. Nucleus - Contains genetic material (DNA) and directs cell activities.
3. Cytoplasm - Jelly-like material inside the cell that contains organelles and allows cell processes.
4. Mitochondria - Produces energy (ATP) for cell activities through cellular respiration.
5. Endoplasmic reticulum - Modifies and transports molecules within the cell.
6. Golgi apparatus - Modifies and packages proteins and lipids for export from the cell.
7. Ribosomes - Site of protein synthesis using
The cell membrane is a complex 3D structure that encircles the cell. It is composed of a phospholipid bilayer with proteins embedded within it. The phospholipid bilayer forms spontaneously, with the hydrophobic tails facing each other and the hydrophilic heads facing outwards towards the extracellular fluid and cytoplasm. This structure allows the membrane to be selectively permeable. Membrane proteins perform important functions like transport, signaling, and identity. Together, the lipid bilayer and embedded proteins create a dynamic structure that is essential for cell integrity and function.
The plasma membrane separates the cell from its environment and regulates the transport of substances into and out of the cell. It has a fluid mosaic structure consisting of a phospholipid bilayer with embedded proteins. Membrane proteins function as ion channels, carriers, receptors, linkers, and cell identity markers. The membrane is selectively permeable and can transport substances via passive diffusion, facilitated diffusion, active transport, osmosis, and bulk transport using vesicles. Active transport requires energy to move molecules against their concentration gradient.
This document provides information on cells at both the prokaryotic and eukaryotic levels. It discusses cell theory and key aspects of prokaryotic cells including their shape, structures like plasmids and mesosomes, and cell envelopes. For eukaryotic cells, it describes the membrane-bound organelles like the nucleus, mitochondria, plastids, Golgi apparatus, endoplasmic reticulum, lysosomes and vacuoles. It also discusses cytoskeletal elements and membrane properties.
Ch 08 - Cell : The unit of Life || Class 11 ||SAQIB AHMED
- Robert Hooke first observed cells in 1665 when examining a slice of cork under a microscope. He saw small compartments separated by walls, which he called cells.
- The Cell Theory, developed by Schleiden and Schwann, states that the cell is the basic unit of structure and function of living things, new cells arise from existing cells, and all organisms are composed of one or more cells.
- Cells come in two main types - prokaryotic cells which lack a nucleus and membrane-bound organelles, and eukaryotic cells which have a nucleus surrounded by a nuclear membrane and other membrane-bound structures.
- Cells are the smallest living units that make up all living things. All cells come from pre-existing cells.
- Cells can be either prokaryotic or eukaryotic. Eukaryotic cells contain a nucleus and membrane-bound organelles, while prokaryotic cells do not have a nucleus or membrane-bound organelles.
- Organelles such as the nucleus, mitochondria, chloroplasts, endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles allow cells to carry out specialized functions and processes like respiration, photosynthesis, protein transport, and waste removal.
- Cells are the smallest living units that make up all living things. All cells come from pre-existing cells.
- Cells can be either prokaryotic or eukaryotic. Eukaryotic cells contain membrane-bound organelles and a nucleus, while prokaryotic cells do not.
- Organelles such as the nucleus, mitochondria, chloroplasts, endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles allow cells to carry out specialized functions and processes like respiration, photosynthesis, protein transport, and waste removal.
- Molecules can move across the cell membrane through passive transport mechanisms like diffusion, osmosis, and facilitated diffusion which do not require
The document discusses the parts of an animal cell and their functions. It aims to teach students to identify and draw the major organelles of an animal cell, including the nucleus, nucleolus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, cytoskeleton, cell membrane, ribosomes, vesicles, and cytosol. Understanding the structure and role of each organelle is important for studying biology at a cellular level.
The cell wall, endomembrane system, and vacuoles are important organelles in plant and fungal cells. The cell wall provides structure, protection, and allows for cell-to-cell interaction. It consists of cellulose, hemicellulose, and pectins in plants. The endomembrane system, including the endoplasmic reticulum, Golgi apparatus, lysosomes coordinates functions like protein transport and modification. The endoplasmic reticulum synthesizes lipids and proteins. The Golgi apparatus packages and modifies proteins and lipids. Lysosomes contain enzymes for digestion. Vacuoles store waste and regulate the cell's internal environment.
This document provides an overview of cell structure and function. It begins by defining key terms like cell membrane, cytoplasm, organelles, and nucleus. It then describes the characteristics of prokaryotic and eukaryotic cells, including their differences. The majority of the document details the structures and functions of various organelles found in eukaryotic cells, such as the nucleus, endoplasmic reticulum, Golgi apparatus, mitochondria, chloroplasts, and vacuoles. It also explains cellular processes like transport across the cell membrane, photosynthesis, and protein synthesis.
General Introduction of Plant Cell & its Organelles by Salman Saeed Lecturer ...Salman Saeed
Cell Biology for Master,s Level Students
Best notes for Biology/Botany/Zoology/Chemistry/Molecular Biology/Biotechnology and Biochemistry Students
Genetics
UCMS Khanewal
The document summarizes key aspects of prokaryotic and eukaryotic cell structure. It describes the three layered cell envelope of most prokaryotic cells, consisting of an outer glycocalyx, middle cell wall, and inner plasma membrane. It also discusses how bacteria can be classified as Gram-positive or Gram-negative based on differences in their cell envelopes and staining. The document then covers additional structures like flagella, pili, and inclusion bodies in prokaryotes, as well as organelles and cytoskeletal elements in eukaryotic cells. It concludes by outlining the fluid mosaic model of the cell membrane and different transport mechanisms like diffusion, osmosis, facilitated transport, and active transport
独中高一生物 2.2.2 nucleus UEC Senior 1 Biology Yee Sing Ong
The document provides information about the structure and function of the nucleus in eukaryotic cells. It discusses that:
1) Most eukaryotic cells contain a single nucleus, though some contain multiple nuclei like muscle and liver cells. The nuclei contain genetic material and can be seen under light microscopes after staining.
2) The nucleus functions to compartmentalize the cell, store and replicate genetic material, and control gene expression and cell metabolism. Cells without a nucleus cannot replicate, grow, or survive for long.
3) The main nuclear structures are the nuclear envelope, nuclear pores, nucleolus, and chromatin. The nuclear envelope separates the nucleus from the cytoplasm, and nuclear pores allow transport between them
The document discusses the cellular level of organization. It defines the cell as the basic structural and functional unit of life. It outlines the cell theory and describes the main components of prokaryotic and eukaryotic cells. The key components of cells discussed include the cell membrane, cytoplasm, and nucleus. The cell membrane is selectively permeable and regulates what passes in and out of the cell. The cytoplasm contains organelles and cytosol. The nucleus contains genetic material and directs the cell's activities.
The document summarizes cell theory and the key discoveries leading to its development. It describes the three main tenets of cell theory proposed by Schleiden, Schwann, and Virchow: 1) all organisms are composed of one or more cells, 2) the cell is the basic unit of life, and 3) all cells come from preexisting cells. It also discusses techniques like cell fractionation and chromatography used to isolate and study cellular components like organelles and proteins.
The plasma membrane acts as a gatekeeper that regulates what enters and exits the cell. It uses both passive and active transport. Passive transport relies on diffusion and moves substances along concentration gradients, while active transport requires energy and can move substances against concentration gradients using mechanisms like the sodium-potassium pump. The plasma membrane is a lipid bilayer with embedded proteins that gives cells structure and allows for selective permeability and transport of molecules in and out of the cell.
Structure and function of cell membraneBlancoScience
The cell membrane is made of a phospholipid bilayer that is selectively permeable. It controls what enters and leaves the cell. The fluid mosaic model describes the cell membrane as being made up of phospholipids, proteins, and cholesterol that move fluidly within the bilayer. The membrane contains transport proteins that allow substances to pass through, including ion channels, carrier proteins, receptor proteins, and enzymes. Carrier proteins can facilitate diffusion or active transport of molecules in or out of the cell.
BIOLOGY FORM 4 CHAPTER 3 - MOVEMENT OF SUBSTANCES ACROSS THE PLASMA MEMBRANENirmala Josephine
The document discusses the movement of substances across cell membranes. It begins by outlining the key topics and learning outcomes, which include explaining passive transport mechanisms like diffusion and osmosis. Diffusion is defined as the passive movement of substances from high to low concentration down a gradient. Facilitated diffusion also occurs passively with the help of channel and carrier proteins. Osmosis is specifically the diffusion of water across membranes to equalize its concentration. The document then details these processes and provides examples to illustrate passive transport in organisms.
The cell membrane is composed of a phospholipid bilayer with embedded proteins. It follows the fluid mosaic model, with phospholipids able to freely move and change places. Membrane proteins come in two types - integral proteins that insert into the membrane and peripheral proteins that attach to surfaces. The membrane controls movement of materials into and out of the cell through passive transport mechanisms like diffusion and facilitated diffusion, as well as active transport powered by protein pumps. It maintains an electrical potential through selective ion transport that powers cellular signaling.
This document provides an introduction to cell structure and function. It defines what cells are and how they were first discovered using microscopes in the 17th century. The three main points of the cell theory are outlined. Cell diversity is discussed in terms of size, shape, and internal organization. The main organelles of animal and plant cells are defined, including their locations and functions. The key differences between plant and animal cells are that plant cells contain cell walls, vacuoles, and plastids.
Eukaryotic and prokaryotic cells differ in their nuclear structure and cell division processes. Eukaryotic cells have a membrane-bound nucleus containing chromosomes and a nucleolus, while prokaryotic cells lack a membrane-bound nucleus and nucleolus. Eukaryotic cells divide their nucleus through mitosis and may undergo meiosis, whereas prokaryotic cells usually divide their nucleoid through binary fission without mitosis or meiosis.
Here are the main parts of the cell labeled:
1. Cell membrane - The outer boundary of the cell that regulates what enters and exits.
2. Nucleus - Contains genetic material (DNA) and directs cell activities.
3. Cytoplasm - Jelly-like material inside the cell that contains organelles and allows cell processes.
4. Mitochondria - Produces energy (ATP) for cell activities through cellular respiration.
5. Endoplasmic reticulum - Modifies and transports molecules within the cell.
6. Golgi apparatus - Modifies and packages proteins and lipids for export from the cell.
7. Ribosomes - Site of protein synthesis using
The cell membrane is a complex 3D structure that encircles the cell. It is composed of a phospholipid bilayer with proteins embedded within it. The phospholipid bilayer forms spontaneously, with the hydrophobic tails facing each other and the hydrophilic heads facing outwards towards the extracellular fluid and cytoplasm. This structure allows the membrane to be selectively permeable. Membrane proteins perform important functions like transport, signaling, and identity. Together, the lipid bilayer and embedded proteins create a dynamic structure that is essential for cell integrity and function.
The plasma membrane separates the cell from its environment and regulates the transport of substances into and out of the cell. It has a fluid mosaic structure consisting of a phospholipid bilayer with embedded proteins. Membrane proteins function as ion channels, carriers, receptors, linkers, and cell identity markers. The membrane is selectively permeable and can transport substances via passive diffusion, facilitated diffusion, active transport, osmosis, and bulk transport using vesicles. Active transport requires energy to move molecules against their concentration gradient.
This document provides information on cells at both the prokaryotic and eukaryotic levels. It discusses cell theory and key aspects of prokaryotic cells including their shape, structures like plasmids and mesosomes, and cell envelopes. For eukaryotic cells, it describes the membrane-bound organelles like the nucleus, mitochondria, plastids, Golgi apparatus, endoplasmic reticulum, lysosomes and vacuoles. It also discusses cytoskeletal elements and membrane properties.
Ch 08 - Cell : The unit of Life || Class 11 ||SAQIB AHMED
- Robert Hooke first observed cells in 1665 when examining a slice of cork under a microscope. He saw small compartments separated by walls, which he called cells.
- The Cell Theory, developed by Schleiden and Schwann, states that the cell is the basic unit of structure and function of living things, new cells arise from existing cells, and all organisms are composed of one or more cells.
- Cells come in two main types - prokaryotic cells which lack a nucleus and membrane-bound organelles, and eukaryotic cells which have a nucleus surrounded by a nuclear membrane and other membrane-bound structures.
This document summarizes several key organelles and structures found in plant cells, including dictyosomes (Golgi apparatus), lysosomes, microbodies, vacuoles, the nucleus, chloroplasts, and cell walls. It also compares plant and animal cells, noting that while they share some similar organelles, plant cells are generally larger, have cell walls, chloroplasts, central vacuoles, and can synthesize all amino acids. The main functions of plant cell organelles are described, such as protein modification in dictyosomes and waste degradation in lysosomes.
Biology Class 11 Chapter 8
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Eukaryotic Cell Structure and Function.pptxEzekielGreen2
Eukaryotic cells are larger and more complex than prokaryotic cells. They contain membrane-bound organelles and have a cytoskeleton that provides structure and aids transport. Key organelles include the nucleus, which houses genetic material, and mitochondria, which generate energy. The endomembrane system includes the endoplasmic reticulum, Golgi apparatus and lysosomes, and facilitates protein transport and modification. Other structures are chloroplasts for photosynthesis and cilia or flagella for motility. Eukaryotic cells have a more complex organization than prokaryotes and can perform more specialized processes and functions.
This document provides a glossary of terms related to plant and animal cell anatomy and organelles. It defines key cellular structures such as the cell membrane, nucleus, mitochondria, chloroplasts, endoplasmic reticulum, Golgi bodies, vacuoles, lysosomes, and ribosomes. It explains their locations within the cell and basic functions. For plant cells specifically, it also defines the cell wall, chloroplasts, and large central vacuole. The summary concludes that plant and animal cells are eukaryotic cells that contain membrane-bound organelles and a nucleus, while prokaryotic cells like bacteria lack these structures.
- The cell is the smallest structural and functional unit of living organisms, generally microscopic and consisting of cytoplasm and a nucleus.
- Robert Hooke first observed cells in 1665 by examining cork under a microscope. Later, van Leeuwenhoek observed living cells using a more powerful microscope.
- Cells contain various organelles that carry out specific functions, including the endoplasmic reticulum, Golgi bodies, mitochondria, ribosomes, lysosomes, centrosomes, plastids, and nucleus. Each organelle has a distinct structure and role in the cell.
Plant cells contain organelles that allow them to carry out photosynthesis and other functions essential for plant growth and survival. The key organelles include chloroplasts for photosynthesis, mitochondria for cellular respiration, a cell wall for structure and support, and a vacuole for storage. Plant cells also have a nucleus, endoplasmic reticulum, Golgi apparatus and cytoskeleton similar to animal cells but adapted for plant functions. Angiosperms and gymnosperms are the two main types of plants differentiated by their reproductive structures.
The document discusses the structure and function of cells. It defines the cell as the basic structural and functional unit of living organisms. The modern cell theory states that all living things are made of cells, cells are the basic units of structure and function, all cells come from preexisting cells, and all cells contain DNA. The document then describes key aspects of cell structure, including the cell membrane, cytoplasm, organelles, cytoskeleton, and nucleus. It also summarizes several important cell functions such as transport, digestion, synthesis of cellular structures, energy production, and movement.
This document provides information on mitochondria, Golgi bodies, and plastids. It describes the key structures and functions of each organelle. Mitochondria are described as the powerhouses of the cell that produce ATP through cellular respiration. Golgi bodies function in transport, packaging, and modification of proteins and lipids. Plastids, such as chloroplasts, chromoplasts, and leucoplasts, play important roles in photosynthesis, pigment storage, and starch/protein storage in plants.
The document provides information about cells including:
1. It summarizes the cell theory which states that cells are the basic units of life, all living things are made of cells, and new cells come from existing cells.
2. It describes the two main types of cells - prokaryotic cells which lack a nucleus and organelles, and eukaryotic cells which have a nucleus and organelles.
3. It details several organelles found in eukaryotic cells and their functions including the nucleus, mitochondria, chloroplasts, endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles.
Specially for Science students.
Understand cell completely with easy language. Easy language for students who are not good in English.
Students who are in high school just read it with conscious mind and grab the points which will help in understanding cell easily as well as it will help you to score good in tests/exams.
For students who are in universities colleges need to understand it completely by putting some efforts.
Human cells contain various organelles that carry out essential functions. The basic components of a cell include the cell membrane, cytoplasm, nucleus, and organelles like mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, and cytoskeleton. The cell membrane forms the boundary of the cell and regulates what enters and exits. The nucleus contains genetic material and influences cell activities. Mitochondria generate energy for cell processes through ATP production. Other organelles are involved in protein synthesis, modification and transport, waste breakdown, and maintaining cell structure.
Microscopes enabled the discovery of cells. Robert Hooke first observed plant and animal cells using a microscope in 1665. The Cell Theory, developed in the 19th century, stated that all organisms are composed of cells, cells are the basic unit of structure and organization, and new cells are produced from existing cells. Electron microscopes allowed observation of intracellular structures. Eukaryotic cells contain membrane-bound organelles that perform specialized functions, including the nucleus, which houses DNA, mitochondria and chloroplasts, which generate energy, and the endoplasmic reticulum and Golgi apparatus, which assemble and transport proteins.
8 105 fa13 inside the cell part 1 skelchristinev40
This document provides an overview of cell structure and function. It begins by outlining the cell theory and basic components of cells. It then distinguishes between prokaryotic and eukaryotic cells, noting that eukaryotes have membrane-bound organelles while prokaryotes do not. The document proceeds to describe various organelles and other structures found in cells, including their functions. It concludes by emphasizing how a cell's structure relates to its specific functions.
The document discusses cells, their structure and function. It explains that cells are the basic unit of life and consist of a nucleus, cytoplasm, organelles, and a plasma membrane. The key components and functions of plant and animal cells are described. Specialized cell types are adapted to their specific functions through differences in shape, structures, and components. Cells combine to form tissues, organs and organ systems that work together to carry out essential life functions.
Diseases can be caused by defects in the endoplasmic reticulum (ER) and Golgi apparatus. Some diseases are due to a lack of signal sequences that direct proteins to the ER, while others are caused by the ER's inability to properly fold proteins or defects in glycosylation. Vesicles are sacs that transport substances within the cell; different types include exosomes, endosomes, lysosomes, and vacuoles. A centrifuge can separate cell components - at 50,000g it can separate mitochondria and chloroplasts but not smaller organelles or ribosomes.
1. The cell is the fundamental unit of structure and function in all living organisms.
2. Cells come in a variety of shapes and sizes, and have a plasma membrane, cytoplasm, and organelles that allow them to carry out functions necessary for life.
3. Eukaryotic cells contain a nucleus and membrane-bound organelles, while prokaryotic cells like bacteria lack these structures.
Eukaryotic cells contain organelles that carry out specialized functions. The organelles include the cell membrane, cytoplasm, nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, ribosomes, and in plant cells, a cell wall, chloroplasts, and central vacuole. The cell membrane forms the boundary of the cell and is selectively permeable. The nucleus houses DNA and controls the cell's activities. Mitochondria generate energy for the cell. The endoplasmic reticulum and Golgi apparatus help synthesize and transport proteins and lipids. Lysosomes break down materials and recycle cell components. Ribosomes produce proteins using instructions from DNA. Plant cells have a cell wall for structure and
1. The document discusses cells, which are the basic structural and functional units of living organisms.
2. It provides details on the history of cell discovery from Hooke to Virchow and outlines the three main principles of cell theory.
3. The document describes the key components of cells including the plasma membrane, nucleus, cytoplasm, and various organelles as well as their structure and functions. It provides examples of unicellular and multicellular organisms.
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Odoo 17 CRM allows us to track why we lose sales opportunities with "Lost Reasons." This helps analyze our sales process and identify areas for improvement. Here's how to configure lost reasons in Odoo 17 CRM
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Tags: Information Security, ISO/IEC 27001, ISO/IEC 42001, Artificial Intelligence, GDPR
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2. Cell Structure
In 1655, the English scientist Robert Hooke coined
the term “cellulae” for the small box-like structures
he saw while examining a thin slice of cork under a
microscope.
3. TWO TYPES OF CELLS
Prokaryotes
•single compartment and surrounded
by the plasma membrane
•lacks a defined nucleus
•simple internal organization
•ex. bacteria, blue-green algae
(cyanobacteria)
Eukaryotes
•
•contain a defined membrane-bound nucleus
• extensive internal membranes that enclose
compartments
main parts: plasma membrane, cytoplasm and nucleus
• ex. all members of the plant and animal kingdom, fungi
(molds* and yeasts**), protozoan*
5. The Structure of Eukaryotic Plant Cell
• A living plant cell is composed of three main parts
namely: cell wall, protoplast and inclusions
6. 1. The Cell
Wall
• The outermost part of the plant cell
• Non-living structure with main chemical
component cellullose (a polysaccharide)
• Other substances which may form part of the
cell wall are lignin, suberin and cutin
• Between neighboring cell walls is a
cementing intercellular layer composed of
pectin substance
• The nonliving layer is often referred to as the
middle lamella
7.
8. PROTOPLASM
a mass of proteins, lipids, nucleic acids,
and water within a cell; except for the
wall, everything in the
cell is protoplasm
• Portions of the protoplast is organized into
protoplasmic bodies with specific functions and
are generally referred to as ORGANELLES
• The protoplast is composed of two main regions,
namely: an outer region called as the
CYTOPLASM and an inner region as the
NUCLEUS
9.
10. • Is bounded by a protoplasmic membrane
called the plasma membrane,
plasmalemma or cell membrane
• The plasma membrane is a selectively
permeable protoplasmic membrane which
regulates the entry and exit of materials in
a cell
11. Other main cytoplasmic structures of plant cells:
1. Mitochondria
2. Ribosomes
3. Endoplasmic Reticulum (ER)
4. Golgi bodies or dictyosomes
5. Lysosomes
6. Plastids
7. Microtubules
12. Mitochondria
• Mitochondria are found in PLANT and animal cells.
• Sites of cellular respiration, ATP synthesis
• Bound by a double membrane surrounding fluid-filled matrix.
• The inner membranes of mitochondria are cristae
• The matrix contains enzymes that break down carbohydrates and
the cristae house protein complexes that produce ATP
THE POWER
HOUSE OF THE
CELL
ATP
13. Ribosomes
• Granular structures visible under electron
microscope
• Protein synthesis
• Ribosomes are composed of a large subunit
and a small subunit.
• Ribosomes can be found alone in the
cytoplasm, in groups called polyribosomes, or
attached to the endoplasmic reticulum.
• Ribosomes are RNA-protein complexes
composed of two subunits that join and
attach to messenger RNA.
– site of protein synthesis
– assembled in nucleoli
14. Endomembrane System
• Compartmentalizes cell, channeling
passage of molecules through cell’s interior.
– Endoplasmic reticulum
• Rough ER - studded with ribosomes
• Smooth ER - few ribosomes
15. Rough ER
• Rough ER is especially abundant in cells that secrete
proteins.
– As a polypeptide is synthesized on a ribosome
attached to rough ER, it is threaded into the
cisternal space through a pore formed by a protein
complex in the ER membrane.
– As it enters the cisternal space, the new protein
folds into its native conformation.
– Most secretory polypeptides are glycoproteins,
proteins to which a carbohydrate is attached.
– Secretory proteins are packaged in transport
vesicles that carry them to their next stage.
16. Smooth ER
• The smooth ER is rich in enzymes and plays a role in a variety of
metabolic processes.
17. The Golgi bodies/ dictyosomes
• The Golgi body is the shipping and receiving center for cell
products.
– Many transport vesicles from the ER travel to the Golgi apparatus
for modification of their contents.
– The Golgi is a center of manufacturing, warehousing, sorting, and
shipping.
– The Golgi apparatus consists of flattened membranous sacs—
cisternae—looking like a stack of pita bread.
– The Golgi sorts and packages materials into transport vesicles.
18. Functions Of The Golgi Bodies
TEM of Golgi apparatus
cis face
(“receiving” side of
Golgi apparatus)
Vesicles move
from ER to GolgiVesicles also
transport certain
proteins back to ER
Vesicles coalesce to
form new cis Golgi cisternae
Cisternal
maturation:
Golgi cisternae
move in a cis-
to-trans
direction
Vesicles form and
leave Golgi, carrying
specific proteins to
other locations or to
the plasma mem-
brane for secretion
Vesicles transport specific
proteins backward to newer
Golgi cisternae
Cisternae
trans face
(“shipping” side of
Golgi apparatus)
0.1 0 µm1
6
5
2
3
4
Golgi
apparatus
19. Lysosomes and Peroxisomes
• Lysosomes – vesicle containing hydrolytic or
digestive enzymes that break down food/foreign
particles
• Peroxisomes - contain enzymes that catalyze
the removal of electrons and associated
hydrogen atoms
20. Lysosome
• Rounded or iregularly-
shaped organelles
bounded by a single
membrane
• Said to play important
role in the destruction
of worn-out or
defective parts of the
cell
• Probably belong to a
group of structures like
microbodies (a) Phagocytosis: lysosome digesting food
1 µm
Lysosome contains
active hydrolytic
enzymes
Food vacuole
fuses with
lysosome
Hydrolytic
enzymes digest
food particles
Digestion
Food vacuole
Plasma membrane
Lysosome
Digestive
enzymes
Lysosome
Nucleus
21. Plastids
• Rounded, oval or irregularly-shaped
protoplasmic bodies of three main
parts:
• Leucoplast
• Chroloplast
• Chromoplast
22. Leucoplast
• Colorless plastids
• Some involved in food storage
• If associated with the starch storage, they
are referred to as amyloplasts
• if associated with oil storage= elaioplasts
• With protein storage = aleurone-plasts
24. Chloroplasts
• A chloroplast is bounded by two membranes enclosing a fluid-filled
stroma that contains enzymes.
• Membranes inside the stroma are organized into thylakoids that house
chlorophyll.
• Chlorophyll absorbs solar energy and carbohydrates are made in the
stroma.
27. • the thickest fibers, are hollow rods about 25
microns in diameter.
– are constructed of the globular protein,
tubulin, and they grow or shrink as more
tubulin molecules are added or removed.
• They move chromosomes
during cell division.
Fig. 7.21b
Microtubules
28. • long, hollow cylinders and made-up
of protein tubulin
• outer diameter of 25nm
• much more rigid
• long and straight and typically have
one end attached to a single
microtubule-organizing center
(MTOC) called a centrosome
29. The Nucleus
• Repository for genetic material
• Chromatin: DNA and proteins
• Nucleolus: Chromatin and ribosomal
subunits - region of intensive ribosomal RNA
synthesis. darkly staining rounded bodies rich
in ribosomal RNA, the type of RNA used in
the formation of ribosomes
• Nuclear envelope: Surface of nucleus bound
by two phospholipid bilayer membranes -
Double membrane with pores
• Nucleoplasm: semifluid medium inside the
nucleus
31. Nucleus
– Nickname: “The Control Center”
– Directs cell activities
• Separated from cytoplasm by nuclear
membrane
• Contains genetic material - DNA
33. Chromosomes
• DNA of eukaryotes is divided into linear chromosomes.
– Exist as strands of chromatin, except during cell division
– Histones associated packaging proteins
34. 3. The Inclusions
• Refer to the nonprotoplasmic structures found
within the protoplast
• Among these are the VACUOLES which are
fluid-filled structures
• The fluid vacuole commonly referred to as the
cell sap
• Contains various dissolved substances such
as anthocyanins (water-soluble pigments) and
various metabolites (e.g. Sugars, inorganic
salts, organic acids, alkaloids)
35. Cont...
• Other inclusions are waste products which may be in
a form of crystals
• The crystals may be contained in vacoules and in the
cytoplasm
• Plant cell may start with many but small vacuoles
• Upon maturity, the small vacuoles may coalesce to
form bigger but fewer vacuoles
• Eventually, a plant cell may have but a SINGLE
LARGE CENTRAL VACUOLE
• Some biologist would consider vacuole as an
oganelle. As such the membrane-bounded structure
containing the cell sap.
36. Crystals in Plant Cells
• Many plant cells contain crystals
which are a product of metabolism
• There are many forms
• Most common are composed of
calcium oxide and calcium carbonate
37. Calcium oxalate crystals
• Generally found in the vacuoles and are as follows:
1. Raphides – needle like crystals which occur singly
or in groups or bundles as in gabi and other succulent plants
2. Prismatic – prism-like or pyramid-like crystals found
in leaves of begonia and bangka-bangkaan
(Rhoeo discolor)
3. Rosette – aggregate of crystals which has
flower-like apperance in santan (Ixora sp.) and
stem of Kutsarita plant
41. Calcium carbonate crystals
• Cystotith- grape-like as seen in a hypodermal cell of the
leaf of Indian rubber tree or ampalaya-like plant.
42. BASIC TYPES OF CELLS
• Despite the diversity of types of stems that have
originated by natural selection, all share a basic, rather
simple organization.
• The same is true for leaves and roots.
• Although we might suspect that numerous types of cells
are present within a plant, actually the various kinds of
plant cells are customarily grouped into three classes
based on the nature of their walls:
Parenchyma, Collenchyma, and Sclerenchyma.
43. 1. PARENCHYMA
• Parenchyma cells have only primary walls that remain
thin.
• Parenchyma tissue is a mass of parenchyma cells. This is
the most common type of cell and tissue, constituting all soft
parts of a plant.
• Parenchyma cells are active metabolically and usually remain
alive once they mature.
• Numerous subtypes are specialized for particular tasks:
44. Parenchyma cells of Geranium
spp.; their walls (green) are thin,
and their vacuoles are large and
full of watery contents that did not
stain. Nuclei were present in all
cells,
45. Subtypes of Parenchyma Cells
A. Chlorenchyma cells
B. Glandular cells
C.Transfer cells
D.(Aerenchyma cells)
46. A. Chlorenchyma cells
• Chlorenchyma cells are parenchyma cells involved in
photosynthesis
• they have an abundance of chloroplasts, and the thinness
of the wall is advantageous for allowing light and carbon
dioxide to pass through to the chloroplasts.
• Other types of pigmented cells, as in flower petals and
fruits, also must be parenchyma cells with thin walls that
permit the pigments in the protoplasm to be seen.
47. Chlorenchyma cells from a
leaf of privet- Ligustrum
vulgare L.
-Intercellular spaces, permit
CO2 rapid diffusion in the
leaf
49. B. Glandular cells
• Glandular cells that secrete nectar, fragrances, mucilage,
resins, and oils are also parenchyma cells; they typically
contain few chloroplasts but have elevated amounts of
dictyosomes and endoplasmic reticulum.
• They must transport large quantities of sugar and
minerals into themselves, transform them metabolically,
then transport the product out.
51. C. Transfer cells
• Transfer cells are parenchyma cells that mediate the short-
distance transport of material by means of a large, extensive
plasma membrane capable of holding numerous molecular
pumps.
• Unlike animal cells, plant cells cannot form folds or
projections of their plasma membranes; instead, transfer
cells increase their surface area by having extensive knobs,
ridges, and other ingrowths on the inner surface of their walls
• Because the plasma membrane follows the contour of all
these, it is extensive and capable of large-scale molecular
pumping.
52. Transfer cells in the salt gland of
Frankenia grandifolia.
The wall ingrowths increase the
surface area of the cell membrane,
providing
more room for salt-pumping proteins in
the membrane.
W. W. Thomson
and R. Balsamo, University of
California, Riverside
53. D. (Aerenchyma cells)
• Parenchyma tissue with extensive connected air
spaces.
• refers to spaces or air channels in the leaves, stems
and roots of some plants, which allows exchange of
gases between the shoot and the root.
• The channels of air-filled cavities provide a low-
resistance internal pathway for the exchange of
gases such as oxygen and ethylene between the
plant above the water and the submerged tissues.
• Aerenchyma is widespread in aquatic and wetland
plants which must grow in hypoxic soils
54.
55. Stem cross-section of Peperomia. The inner
part of the stem is mostly parenchyma cells.
56. • Some parenchyma cells function by dying at maturity.
• Structures such as stamens and some fruits must open
and release pollen or seeds; the opening may be
formed by parenchyma cells that die and break down or
are torn apart.
• Large spaces may be necessary inside the plant body;
some of these are formed when the middle lamella
decomposes and cells are released from their
neighbors.
• In other cases, the space is formed by the degeneration
of parenchyma cells.
• In a few species, such as milkweeds, as parenchyma
cells die, their protoplasm is converted metabolically
into mucilage or a milky latex.
57. • Parenchyma tissue that conducts nutrients over long distances
is phloem
• Parenchyma cells are relatively inexpensive to build because
little glucose is expended in constructing the wall's cellulose
and hemicellulose.
• Each molecule incorporated into a wall polymer cannot be
used for other purposes such as the generation of ATP or the
synthesis of proteins.
• Consequently, it is disadvantageous to use a cell with thick
walls any time one with thin walls would be just as functional.
58. 2. COLLENCHYMA CELLS
• Collenchyma cells have a primary wall that
remains thin in some areas but becomes thickened
in other areas, most often in the corners.
• The nature of this wall is important in understanding
why it exists and how it functions in the plant.
• Like clay, the wall of collenchyma exhibits plasticity,
the ability to be deformed by pressure or tension and
to retain the new shape even if the pressure or tension
ceases.
59. • Collenchyma is present in elongating shoot tips
that must be long and flexible, such as those of
vining plants like grapes, as a layer just under the
epidermis or as bands located next to vascular
bundles, making the tips stronger and more resistant
to breaking.
• But the tips are still capable of elongating because
collenchyma can be stretched.
• In species whose shoot tips are composed only of
weak parenchyma, the tips are flexible and delicate
and often can be damaged by wind; the elongating
portion must be very short or it simply buckles under
its own weight.
60. Stem cross-section of Peperomia. Masses of collenchyma cells
often occur in the outer parts of stems and leaf stalks. The
collenchyma forms a band about 8 to 12 cells thick.
61. • It is important to think about the method by which
collenchyma provides support.
• If a vine or other collenchyma-rich tissue is cut off from
its water supply, it wilts and droops; the collenchyma is
unable to hold up the stem.
• Parenchyma cells are needed in the inner tissues for
support. Collenchyma and turgid parenchyma work
together like air pressure and a tire: The tire or inner
tube is extremely strong but is useless for support
without air pressure.
• Similarly, air pressure is useless unless it is confined by
a container.
• In stems, the tendency for parenchyma to expand is
counterbalanced by the resistance of the collenchyma,
and the stem becomes rigid.
62. The shoot tips
of long vines
need the plastic
support of
collenchyma
while their
stems are
elongating
63. • Because the walls of collenchyma cells are thick, they
require more glucose for their production.
• Collenchyma is usually produced only in shoot tips and
young petioles, where the need for extra strength justifies
the metabolic cost.
• Subterranean shoots and roots do not need collenchyma
because soil provides support, but the aerial roots of
epiphytes such as orchids and philodendrons have a
thick layer of collenchyma
64. 3. SCLERENCHYMA CELLS
• The third basic type of cell and tissue, sclerenchyma,
has both a primary wall and a thick secondary wall that
is almost always lignified.
• These walls have the property of elasticity: They can be
deformed, but they snap back to their original size and
shape when the pressure or tension is released.
• Sclerenchyma cells develop mainly in mature organs that
have stopped growing and have achieved their proper
size and shape.
65.
66. A stem of bamboo was treated with a mixture of nitric acid and chromic acid to
67. These are sclereids; they are more or less cuboidal, definitely not long like fibers.
These have remained alive at maturity, and nuclei & cytoplasm are visible in
68. astrosclereids (star-shaped sclereids), shines brightly because its cellulose molecules
are packed in a tight, crystalline form, giving the wall extra strength .
69. • Deforming forces such as wind, animals, or snow would
probably be detrimental.
• If mature organs had collenchyma for support, they would be
reshaped constantly by storms or animals, which of course
would not be optimal.
• For example, while growing and elongating, a young leaf
must be supported by collenchyma if it is to continue to grow.
• But once it has achieved its mature size and shape, some
cells of the leaf can mature into sclerenchyma and provide
elastic support that maintains the leaf's shape.
• Unlike collenchyma, sclerenchyma supports the plant by its
strength alone; if sclerenchyma-rich stems are allowed to wilt,
they remain upright and do not droop.
70. • Parenchyma and collenchyma cells can absorb water so
powerfully that they swell and stretch the wall, thereby
growing; sclerenchyma cell walls are strong enough to
prevent the protoplast from expanding.
• The rigidity of sclerenchyma makes it unusable for growing
• shoot tips because it would prevent further shoot elongation.
• Sclerenchyma cells are of two types—conducting
sclerenchyma and mechanical sclerenchyma.
• The mechanical sclerenchyma is subdivided into long fibers
and short sclereids , both of which have thick secondary
walls.
• Because fibers are long, they are flexible and are most often
found in areas where strength and elasticity are important.
71. • The wood of most flowering plants contains abundant
fibers, and their strength supports the tree while their
elasticity allows the trunk and branches to sway in the
wind without breaking (usually) or becoming permanently
bent .
• The fiber-rich bark is important not in holding up the tree
but in resisting insects, fungi, and other pests.
• Sclereids are short and more or less
isodiametric(cuboidal).
• Because sclereids have strong walls oriented in all three
dimensions, sclerenchyma tissue composed of sclereids
is brittle and inflexible.
74. Parenchyma
This tissue is composed of large,
thin walled cells having a single
large vacuole.
This tissue is found in the soft parts
of the plant like the cortex(outer
region) and pith(inner region) of the
roots and stems.
The cells present in these tissues
are living.
These cells store food for the plant,
and thus they also provide
temporary support for the plants.
When parenchymatous cells are
present in leaves, they sometimes
contain chlorophyll, and thus are
green in colour. This tissue is then
referred to as chlorenchyma.
Potatoes are made up of mainly
Parenchyma tissue cells.
75. Collenchyma
This tissue is made up of
cells from the parenchyma
tissue which become
elongated and have thick cell
walls at the corners. This
diagram illustrates the
difference between
parenchyma and
collenchyma cells. The
collenchyma cells are
elongated and thick at the
corners.
This tissue is found mainly in
the leaf stalks and below the
epidermis of stems.
It gives support for the parts
of a plant like leaves, stems,
branches.
76. Sclerenchyma
Sclerenchyma is made up of
thin, narrow and long cells
having very thick cell walls
due to deposition of lignin.
These cells are thin because
they are all dead cells, having
no functions to perform and so
no organelles inside the cell
require space.
They are thick at the cell walls
and thus these cells provide
rigid support for the plant as
they are hard and supportive.
That is why the tissue is
named "Sclerenchyma", as
scleros means hard.
Sclerenchyma tissue is
present in stems of plants and
the veins of leaves in plants. It
provides strength to plant
parts.