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CELL BIOLOGY ZHOU Yong Department of Biology Xinjiang Medical University 1 Chapter 1 Introduction to the cell Learning Objectives 1.About Cell Biology 2.Look briefly at the history of cell theory; 3.Consider the basic properties of cells; 4.Compare some characteristics of two different classes of cells: prokaryotes and eukaryotes; 5.Comprehend a special life: viruses 2 Teaching Requirements • 1. Mastering: definition of Cell and Cell Biology; main differences of structure of prokaryocytes and eukaryocytes. • 2. Comprehending: cell theory and cell volume conservation law. • 3. Understanding: simple history of cell biology; basic properties of the cell; main stages of the formation and evolution of cell. 3 1. About “Cell Biology” What? Forwhy? How to study? The NIH of USA(1988): “What is popular in research today?” 3 kinds of diseases : cancer cardiovascular diseases infectious diseases:AIDS,hepatitis 5 research fields : cell cycle control ; cell apoptosis; cellular senescence; signal transduction; DNA damage and repair. What we know//How we know. 4 2. 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 drawed in 1665 5 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(1804~1834) Schwann(1810~1882) 3.All cells arise only from preexisting cells by division. 6 3. Why are cells the basic units of life? A. The cell is the structural unit of life, All organisms is make up of cells. 7 B.The cell is the functional unit of organisms. All metabolic activity is based on cells. 8 C. The cell is the foundation of reproduce, and the bridge of inheritance. 9 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 and rudiments of all other organs 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. 10 E. Cell (nucleus) is totipotent, which can create a new organism of the same type As a general rule, the cells of a multicellular organism all contain the same set of genes. For animals, the first evidence that even highly specialized cell carry a full complement of genes was verified by the experiment of tadpole nuclei transplanting into unfertilized egg that had been deprived of its own nucleus. Some can develop swimming tadpoles. This is animal cloning. An especially dramatic example of animal cloning was reported in 1997. Dolly the first animal ever cloned from a cell derived from an adult. 11 Dolly and her daughter The process of cloning Dolly Is there any practical value to such technology? 12 4. 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. 13 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 univesity,in 1951 14 D. Cells are able to respond to stimuli via surface receptors that sense changes in the chemical environment. Cells within plant or animal respond to stimuli less obviously than single-celled protist. But they respond. They posses 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. 15 5.The Size of Cells a) Diameter b) Measured in units of micrometers: 1μm=10-6 meter nanometers: 1nm=10-9 meter c) Cell size is limited: nucleus/cytoplasm ratio; surface area/volume ratio; substances can efficiently travel through the cytoplasm via diffusion. 16 6. Two fundamentally different classes of cells: Prokaryotes and eukaryotes A. Prokaryotic and eukaryotic cells are distinguished by the size and the types of internal structures, or organelles, especially if there is nuclear envelope. Bacteria are prokaryotes, they arose 3.5 billion years ago; Blue algae, fungi, plants, and animals are eukaryotes. The first eukaryotes arose 1.5 billion years ago. 17 B. Characteristics that distinguish prokaryotic and eukaryotic cells pp.14 Table 1-1 18 19 7.Types of Prokaryotic Cells: Two Subkingdoms Tree of life has three primary branches. A. Subkingdom Archaea B. Subkingdom Bacteria Most Bacteria and Archaea have 1000-4000 genes The smallest known cells ---the Mycoplasma 0.1~0.3μm; smallest genome: 482 genes, minimal essential gene:256 20 Bacterial Cell • cell wall • cell membrane • Nucleoid region • ribosomes • flagellum 21 8. Viruses 1.Viruses are pathogens first described in the late 1800s. 2. Viral structure: a)The genetic material: Single- or doublestranded DNA or RNA. b)obligatory intracellular parasites. Virus diversity 3.Viral infection types: a)Lytic infection; b)integrated infection 22 9. Reference book Alberts B et al. Essential Cell Biology. New York and London:Garland publishing,Inc. 1998 Alberts B et al. Molecuar 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 Ed. 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 Lodish H. et al. Molecular Cell Biology. 4th Ed. Scientific American Books,Inc. 2000. 23 REVIEW QUESTIONS Eukaryotic cells usually contain Unlike eukaryotes, prokaryotes lack A. a nucleus. A. a plasma membrane. B. mitochondria. B. DNA. C. ribosomes. C. ribosomes. D. microtubules. D. nuclei. E. all of the above. E. molecular motors E. These are all typical features of eukaryotic cells. D. Eukaryotes have all of these, but prokaryotes do not have nuclei. Rather, the DNA is free in the cytoplasm 24 1,000,000 nm is equal to A. 1 μm. B. 10 μm. C. 1 mm. D. 10 mm. E. 1 m. C. The international system prefixes used in this book are m for milli, meaning 10-3, μ for micro, meaning 10-6, and n for nano meaning 10-9. Thus 1,000,000 times 10-9 is 10-3 so 1,000,000 nm is equal to 1 mm. 25