Cell biology - lect. 1 A - 24.pdf

‫ﺑﺴﻢ ﷲ اﻟﺮﺣﻤﻦ اﻟﺮﺣﯿﻢ‬ ‫ﻋﺎم دراﺳﻲ ھﯿﻦ ﻟﯿﻦ ﻳﺎ رب اﻟﻌﺎﻟﻤﯿﻦ‬ ‫‪Ass.Prof. Hanaa Elbadawy‬‬ ‫‪1‬‬  Dr. Hanaa Elbadawy Botany and Microbiology Deprt....

‫ﺑﺴﻢ ﷲ اﻟﺮﺣﻤﻦ اﻟﺮﺣﯿﻢ‬ ‫ﻋﺎم دراﺳﻲ ھﯿﻦ ﻟﯿﻦ ﻳﺎ رب اﻟﻌﺎﻟﻤﯿﻦ‬ ‫‪Ass.Prof. Hanaa Elbadawy‬‬ ‫‪1‬‬  Dr. Hanaa Elbadawy Botany and Microbiology Deprt. [email protected] u Course title: Cell biology u Course coordinator and instructors: Dr. Hanaa and Dr. Amira Course code: BTBio 111 u Credit hours: 3 hours (theoretical + practical ) u Lecture: (alternate topics weekly) u Lab : ( Plant cell biology) u – (Animal cell biology) u Total Marks: 100 ( 50 + 50) mid term: 10 (5+5) # may be at week 7 Practical exam: 30 (15 + 15) Final Exam 30 + 30 Ass.Prof. Hanaa Elbadawy 2  Course book u FOURTH EDITION u ESSENTIAL CELL BIOLOGY u © 2014 by Bruce Alberts, Dennis Bray, Karen Hopkin, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, and Peter Walter Ass.Prof. Hanaa Elbadawy 3  Course contents u Plant cell components 1 u Plant cell components 2 u Plant tissues u Enzymes and biological cell u Plant hormones and growth regulation u ------------------------------------------------------------- u Animal cell Chemistry and components u Endomembrane system and Cytoskeleton u Different types of animal tissues u Cell cycle and cell differentiation u Apoptosis and cancer Ass.Prof. Hanaa Elbadawy 4 Introduction Cell biology u This topic is dealing with the study of cells and their structure, function, and behavior (cell to cell communication)—that we must look for an answer to the question of what life is and how it works. u Biologists estimate that there may be up to 100 million distinct species of living things on our planet. All living things (or organisms) are built from cells: small, membrane enclosed units filled with a concentrated aqueous solution of chemicals u These cells have the ability to create copies of themselves by growing and then dividing in two. The simplest forms of life are solitary cells. Higher organisms, including ourselves, are communities of cells derived by growth and division from a single cell. some plant is a vast colony of individual cells, each of which performs a specialized function that is regulated by intricate systems of cell-to-cell communication. u Higher plants formed of systems (root, shoot) -----different organs (stem, leaves, flowers , fruits) ----- vast number of cells. Ass.Prof. Hanaa Elbadawy 5 The Prokaryotic Cell u Of all the types of cells revealed by the microscope, bacteria have the simplest u structure and come closest to showing us life stripped down to its essentials. Indeed, a bacterium do not contain a nucleus to hold its DNA. u This property—the presence or absence of a nucleus—is used as the basis for a simple but fundamental classification of all living things. u Organisms whose cells have a nucleus are called eukaryotes (from the Greek words eu, meaning “well” or “truly,” and karyon, a “nucleus”). u Organisms whose cells do not have a nucleus are called prokaryotes (from pro, meaning “before”). Ass.Prof. Hanaa Elbadawy 6 Differences between Prokaryotes and Eukaryotes https://www.brainkart.com/article/Different-Between-Prokaryotic-and-Eukaryotic-Cell 7 Ass.Prof. Hanaa Elbadawy  Flagellum This Photo by Unknown Author is licensed under CC BY 8 Ass.Prof. Hanaa Elbadawy  100 μm 25 μm 10 μm 5 μm 1 μm A B C D E u (A) photo of a single nerve cell from a mammalian brain. u (B) This protozoan—a single giant cell—swims by means of the beating cilia that cover its surface. u (C) Chlamydomonas. This type of single-celled green algae is found all over the world—in soil, fresh water, oceans, and even in the snow at the top of mountains. The cell makes its food like plants do—via photosynthesis—and it pulls itself through the water using its paired flagella to do the breaststroke. u (D) Saccharomyces cerevisiae. This yeast cell, used in baking bread, reproduces itself by a process called budding. u (E) Helicobacter pylori. This bacterium—a causative agent of stomach ulcers Ass.Prof. Hanaa Elbadawy 9 Characteristics of plant cell https://www.brainkart.com/article/ Ass.Prof. Hanaa Elbadawy 10 Plasmodesma This Photo by Unknown This Photo Author by Unknown is licensed Author underisCC licensed BY-SA-NC under CC BY-SA-NC 11 Ass.Prof. Hanaa Elbadawy  All living organisms are constructed from cells. A colony of bacteria, a butterfly, a rose, and a dolphin are all made of cells that have a fundamentally similar chemistry and operate according to the same basic principles. Cells Under the Microscope The earliest cell biologists began by simply looking at tissues and cells, and later breaking them open or slicing them up, attempting to view their contents. Cells were not made visible until the seventeenth century, when the microscope was invented. Light microscopes use visible light to illuminate specimens. Electron microscopes, invented in the 1930s, using beams of electrons instead of beams of light as the source of illumination, making some of the larger molecules visible individually. These and other forms of microscopy remain vital tools in the modern cell biology laboratory. Ass.Prof. Hanaa Elbadawy 12 The Invention of the Light Microscope Led to the Discovery of Cells u The development of the light microscope depended on advances in the production of glass lenses. u By the seventeenth century, lenses were powerful enough to make out details invisible to the naked eye. u Using an instrument equipped with such a lens, Robert Hooke examined a piece of cork and in 1665 reported to the Royal Society of London that the cork was composed of a mass of minute chambers. He called these chambers “cells,”. u Later, Hooke and his Dutch contemporary Antoni van Leeuwenhoek were able to observe living cells, u The light microscope allows us to magnify cells up to 1000. u Three things are required for viewing cells in a light microscope. u First, a bright light must be focused onto the specimen by lenses in the condenser. u Second, the specimen n must be carefully prepared to allow light to pass through it. u Third, an appropriate set of lenses (objective and eyepiece) must be arranged to focus an image of the specimen in the eye Ass.Prof. Hanaa Elbadawy 13 Fluorescence microscope u Fluorescent dyes used for staining cells are detected with the aid of a fluorescence microscope. u Some such dyes bind specifically to particular molecules in cells and can reveal their location when examined with a fluorescence microscope. u An example is the stain for DNA shown here (green ) Ass.Prof. Hanaa Elbadawy 14 TRANSMISSION MICROSCOPY ELECTRON (TEM) v Micrograph below shows a small region of a cell. v The tissue has been chemically fixed, v Embedded in plastic, v Cut into very thin sections. v These sections have then been stained with salts of some metals. Ass.Prof. Hanaa Elbadawy 15  SCANNING ELECTRON TRANSMISSION MICROSCOPY SEM) u In the scanning electron microscope (SEM), the specimen, which has been coated with a very thin film of a heavy metal, u The surface of the specimen is measured by the detector, and is used to control the intensity of successive points in an image built up on a video screen. u The microscope creates striking images of three-dimensional u objects with great depth of focus and can resolve details down to somewhere between 3 nm and 20 nm, depending on the instrument. Ass.Prof. Hanaa Elbadawy 16 Prokaryotes u are typically spherical, rod-like, or spiral-shaped. u Prokaryotes often have a tough protective coat, or cell wall, surrounding the plasma membrane, which encloses a single compartment containing the cytoplasm and the DNA. u Many prokaryotic cells can duplicate themselves in as little as 20 minutes. u In 11 hours, by repeated divisions, a single prokaryote can give rise to more than 8 billion progeny (which exceeds the total number of humans presently on Earth). e.g., spherical cells rod-shaped cells spiral cells Streptococcus Salmonella Treponema Ass.Prof. Hanaa Elbadawy 17 u Most prokaryotes live as single-celled organisms, u although some join together to form chains, clusters, or other organized multicellular structures. u Members of this class exploit an enormous range of habitats, from hot puddles of volcanic mud to the interiors of other living cells. u Some are aerobic, using oxygen to oxidize food molecules; some are strictly anaerobic and are killed by the slightest exposure to oxygen. Ass.Prof. Hanaa Elbadawy 18 Plant cell u A typical plant cell has prominent cell wall, a large vacuole and plastids in addition to other organelles present in animal cell. Ass.Prof. Hanaa Elbadawy 19 Ass.Prof. Hanaa Elbadawy 20 Cell Wall u Cell wall is the outermost protective cover of the cell. u It is present in bacteria, fungi and plants whereas it is absent in animal cell. u It was first observed by Robert Hooke. u It is an actively growing portion. It is made up of different complex material in various organism. u In bacteria: it is composed of peptidoglycan, u in fungi: chitin and fungal cellulose, u in algae: cellulose, galactans and mannans. u In higher plants: it is made up of cellulose ( units of glucose), hemicellulose (units of mannose , xylene, arabinose), pectin, lignin, cutin, suberin and silica. Ass.Prof. Hanaa Elbadawy 21 https://www.google.com/worldindustrialreporter.com  Cell Wall in plant cell u It is a rigid layer which is composed of cellulose, glycoproteins, lignin, pectin and hemicellulose. u The primary function of the cell wall is to protect and provide structural support to the cell. The plant cell wall is also involved in protecting the cell against mechanical stress and to provide form and structure to the cell. u It also filters the molecules passing in and out of the cell. u The formation of the cell wall is guided by microtubules. It consists of three layers, namely, primary, secondary and the middle lamella. The primary cell wall is formed by cellulose laid down by enzymes. In plant, cell wall shows three distinct regions (a) Primary wall (b) Secondary wall (c) Middle lamellae. 22 Ass.Prof. Hanaa Elbadawy u a. Primary wall u It is the first layer inner to middle lamellae, primarily consisting of loose network of cellulose microfibrils in a gel matrix. u It is thin, elastic and extensible. u In most plants the microfibrils are made up of cellulose oriented differently based on shape and thickness of the wall. u The matrix of the primary wall is composed of hemicellulose, pectin, glycoprotein and water. Cells such as parenchyma and meristems have only primary wall. https://www. researchgate.net Ass.Prof. Hanaa Elbadawy 23 u b. Secondary wall Secondary wall is laid during maturation. It plays a key role in determining the shape of a cell. It is thick, inelastic and is made up of cellulose and lignin. The secondary wall is divided into three sublayers termed as S1, S2 and S3 where the cellulose microfibrils are compactly arranged with different orientation forming a laminated structure and the cell wall strength is increased. u c. Middle lamellae It is the outermost layer made up of calcium and magnesium pectate, deposited at the time of cytokinesis. It is a thin amorphous layer which cements two adjacent cells. Ass.Prof. Hanaa Elbadawy 24 Plasmodesmata and Pits u Plasmodesmata act as a channel between the protoplasm of adjacent cells through which many substances pass through. 25 Ass.Prof. Hanaa Elbadawy Pits u Few regions the secondary wall layer is laid unevenly whereas the primary wall and middle lamellae are laid continuously such regions are called pits. u The pits of adjacent cells are opposite to each other. Ass.Prof. Hanaa Elbadawy 26  https://ib.bioninja.com.au/higher-level/topic-9-plant- biology/untitled-6/xylem-structure.html Ass.Prof. Hanaa Elbadawy Border pits in L. S. https://images.app.goo.gl/NrGoEzao6crvDiNH9 Ass.Prof. Hanaa Elbadawy Functions of cell wall The cell wall plays a vital role in holding several important functions given below 1) Offers definite shape and rigidity to the cell. 2) Serves as barrier for several molecules to enter the cells. 3) Provides protection to the internal protoplasm against mechanical injury. 4) Prevents the bursting of cells by maintaining the osmotic pressure. Ass.Prof. Hanaa Elbadawy 29 Cell membrane u It is the semi-permeable membrane that is present within the cell wall. u It is composed of a thin layer of protein and fat. u The cell membrane plays an important role in regulating the entry and exit of specific substances within the cell, a phenomenon known as permeability. u For instance, cell membrane keeps toxins from entering inside, while nutrients and essential minerals are transported across. Ass.Prof. Hanaa Elbadawy 30  Permeability Transport of Solutes across Cell Membrane: Single unit membrane Double unit membrane Plasma membrane Mitochondria Tonoplast Chloroplast Endoplasmic reticulum nucleus Ass.Prof. Hanaa Elbadawy 31