Introduction_lecture 1.pptx

Kwame Nkrumah University of Science & Technology, Kumasi, Ghana Molecular Biology of the Cell Amma Larbi(PhD) Email: [email protected] 0204734274 Historical perspectives: Cells and genomes Lear...

Kwame Nkrumah University of Science & Technology, Kumasi, Ghana Molecular Biology of the Cell Amma Larbi(PhD) Email: [email protected] 0204734274 Historical perspectives: Cells and genomes Learning Objectives About Molecular Cell Biology Brief history of cell theory Basic properties of cells Comparison of some characteristics of two different classes of cells: prokaryotes and eukaryotes; Comprehend a special life: viruses Techniques in molecular cell biology www.knust.edu.gh About “Molecular Cell Biology” It is the study of cell structure and function using a molecular approach. Understanding molecular biology of cells is fundamental for research in basic sciences and for development of applications in medicine, agriculture and biotechnology. 3 www.knust.edu.gh  About “Molecular Cell Biology” What is popular in research today ？ What?  3 kinds of diseases ：  cancer  cardiovascular diseases  infectious diseases ： AIDS ， hepatitis  5 research fields ：  cell cycle control ；  cell apoptosis ； How to  cellular senescence ；  signal transduction ； study?  DNA damage and repair. 4 www.knust.edu.gh Three top research fields: No1: Signal transduction ； No2: Cell apoptosis ； No3: Genome and post-genomic analysis 。 5 www.knust.edu.gh The Cell Theory: A Brief History The discovery of cells followed from the invention of the microscope In 1665, Robert Hooke saw a network of tiny boxlike compartments that reminded him of a honeycomb. He called these little compartments “cellulae”, a Latin term meaning little room. It is from this word we get our present-day term, cell. The microscope used by Robert Hooke and the honeycomb-like network of “cell” he drew in 1665. www.knust.edu.gh Cell theory has three basic tenets: 1. All organisms are composed of one or more cells. 2.The cell is basic unit of structure and function for all organisms. Schleiden (1804-1881) Schwann (1810-1882) 3.All cells arise only from preexisting cells by division. www.knust.edu.gh Why are cells the basic units of life? A. The cell is the structural unit of life, all organisms is made up of cells. www.knust.edu.gh B.The cell is the functional unit of organisms. All metabolic activity is based on cells. 9 www.knust.edu.gh C. The cell is the foundation of reproduce, and the bridge of inheritance. 10 www.knust.edu.gh  D. The cell is the growing and developing basis of life Human fetal development. (a)At 5 weeks, limb buds, eyes, the heart, the liver have started to develop in the embryo, which is only about 1cm long. (b)Growth and development of the offspring, now called a fetus, continue during the second trimester. This fetus is 14 weeks old and about 6cm long. (c)The fetus in this photograph is 20 weeks old. Now the fetus grows to about 30cm in length. www.knust.edu.gh E. Cell (nucleus) is totipotent, which can create a new organism of the same type An especially dramatic example of animal cloning was reported in 1997. Dolly the first animal cloned from a cell derived from an adult. www.knust.edu.gh  Dolly and her daughter The process of cloning Dolly Is there any practical value to such technology? www.knust.edu.gh  Basic properties of cells A. Cells are highly complex and organized, capable of self- regulation; Cells acquire and utilize energy. B. All cells share similar structure, composition and metabolic features: Plasma membrane, DNA/RNA, and Ribosome. www.knust.edu.gh C. Cells are capable of producing more of themselves, even grow and reproduce in culture for extended periods. HeLa cells are cultured tumor cells isolated from a cancer patient named Henrietta Lacks in 1951. It is the first human cell to be kept in culture for long periods of time and is still used today. Johns Hopkins university, in 1951 www.knust.edu.gh D. Cells are able to respond to stimuli via surface receptors that sense changes in the chemical environment. Cells possess receptors that interact with substances in the environment in highly specific ways. For example, the receptor on the cell surface can respond to hormones and growth factors. www.knust.edu.gh The Size of Cells a) diameter b) Measured in units of micrometers: 1um=10-6 meter nanometers: 1nm=10-9 meter c) Cell size is limited:  nucleus/cytoplasm ratio  surface area/volume ratio 17 www.knust.edu.gh The three domains of life In the early part of the 20th century, scientists divided all life into 2 kingdoms. Animal and plant. Bacteria were regarded as plants. After the middle of the century, this classification was abandoned in favor of a five-kingdom system. www.knust.edu.gh Classification by Kingdom Kingdom Phylum Class Order Family Genus Species www.knust.edu.gh  Further Classification In the late 1970s,Carl Woese performed sequencing studies on the ribosomal RNA genes of many different organisms Finding: a class of organisms originally classified as bacteria have rRNA genes that are more similar to those of eukaryotes than they are to those of classical bacteria This class was named archaebacteria to distinguish them from true bacteria, eubacteria Further molecular evidence showed that these were not actual bacteria. Woese named them archae These studies led to six kingdoms: Eubacteria, Archaebacteria, fungi, protista, plantae and animalia www.knust.edu.gh  Current Classification Now biologists use a new classification above the kingdom: 3 domains of life Bacteria, Archae, Eukaryote Domain bacteria and domain Archae = Prokaryotes: organisms with prokaryotic cells Molecular evidence shows Achaea are related to eukaryotic organisms as they are to bacteria 22 www.knust.edu.gh 23 www.knust.edu.gh Two different classes of cells: Prokaryotes and eukaryotes A. Prokaryotic and eukaryotic cells are distinguished by the size and the types of internal structures, especially if there is nuclear envelope. Bacteria are prokaryotes, they arose 3.5 billion years ago; Protists, fungi, plants, and animals are eukaryotes. The first eukaryotes arose 1.5 billion years ago. www.knust.edu.gh B. Characteristics that distinguish prokaryotic and eukaryotic cells (1) Complexity: Prokaryotes are relatively simple; eukaryotes are more complex in structure and function www.knust.edu.gh (2) Genetic material: All cells store their genetic information in the same liner chemical code (DNA) a. Packaging: Prokaryotes have a nucleoid region whereas ekukaryote have a true, membrane-bound nucleus. b. Amount:Eukaryotes have several orders of magnitude more genetic material than prokaryotes.(yeast:4.6mm DNA, encoding about 6200 proteins) c. Form: Eukaryotes have many chromosomes that are made of both DNA and protein whereas prokaryotes have a single ,“naked” DNA chromosome www.knust.edu.gh (3) Cytoplasm: Eukaryotes have membrane- bound organelles and cytoskeletal proteins; prokaryotes have neither. Both have ribosomes, although they differ in size. (4) Cellular reproduction: Eukaryotes divide by mitosis; prokaryotes divide by simple fission. (5) Locomotion: Eukaryotes use both cytoplasmic movement, and cilia and flagella; prokaryotes have flagella, but they differ in both form and mechanism from eukaryotic flagella. www.knust.edu.gh Differences  Viruses 1.Viruses are first described in the late 1800s. 2. Viral structure: a) The genetic material: Single-or double-stranded DNA or RNA. b) obligatory Several types of viral genomes intracellular parasites. www.knust.edu.gh 3. Viral infection types: a) Lytic infection; b) integrated infection 4. Viral origins: a)Viruses had to arise after their hosts evolved. b)Viruses probably arose as fragments of host chromosomes. www.knust.edu.gh  Techniques in Cell Biology Cell structure study methods Cytological Study methods Component study methods Cytological engineering www.knust.edu.gh  (1) Cell structure study methods Bright microscope Light Fluorescence microscope microscope Laser scanning confocal microscope Phase contrast microscope Microscope Transmission electron microscope Electron Scanning electron microscope microscope Scanning tunneling microscope Atomic force microscope www.knust.edu.gh Figure. Resolving power. Sizes of cells and their components drawn on a logarithmic scale, indicating the range of objects that can be readily resolved by the naked eye and in the light and electron microscopes. The following units of length are commonly employed in microscope: 1 m = 100cm = 1000mm =106 µm (micrometer) = 109 nm (nanometer) 32 www.knust.edu.gh  A. Light Microscope The most important property of microscope is not its magnification but its resolving power. Resolution ： its ability to distinguish between two very closely positioned objects. www.knust.edu.gh The Light Microscope 34 www.knust.edu.gh B. Fluorescence microscope （荧光显微镜） www.knust.edu.gh Fluorescence chemical theory Specimen absorbs light at one wavelength and emits light (fluoresce) at a specific and longer wavelength. Most fluorescent dyes emit visible light. www.knust.edu.gh Figure 1-9. Interference between light waves. When two light waves combine in phase, the amplitude of the resultant wave is larger and the brightness is increased. Two light waves that are out of phase partially cancel each other and produce a wave whose amplitude, and therefore brightness, is decreased. 37 www.knust.edu.gh Figure 1-10. Fluorescent dyes. The structures of fluorescein and tetramethylrhodamine, two dyes that are commonly used for fluorescence microscope. Fluorescein emits green light, whereas the rhodamine dye emits red 38 www.knust.edu.gh light. Image of a mouse cell microtubule cytoskeleton (green), the nucleus (blue) and Actin (red) www.knust.edu.gh (2) Components study methods Flow Cytometry Cell component isolation Centrifugation www.knust.edu.gh www.knust.edu.gh 42 www.knust.edu.gh Cell engineering www.knust.edu.gh Cell fusion technique  Attachment Entr Uncoating y Release Transcription Replication Assembly Translation Reference books: Alberts B et al. Essential Cell Biology. New York and London ： Garland publishing ， Inc. 1998 Alberts B et al. Molecular Biology of the Cell, 3rd ed. New York and London ： Garland Publishing ， Inc. 1994; 3rd 2002. Becker W.M. et al. The World of the Cell. Fourth edition. The Benjamin/Cummings Publishing Company. 2000. Gerald Karp. Cell and Molecular Biology ： concepts and experiments ， 2nd Edition. Published by John Wiley & Sons,Inc. 1999 Gerald Karp. Cell and Molecular Biology ： concepts and experiments ， 3rd Edition. Published by John Wiley & Sons,Inc. 2002 46 www.knust.edu.gh Lodish H. et al. Molecular Cell Biology. 4th Ed. Scientific American 47 www.knust.edu.gh  THANK YOU 48 www.knust.edu.gh 08/04/2024 48