Chapter 1 - Introduction to Cell Biology PDF

Chapter 1: Introduction to Cell Biology  Outline the early history of Cell Biology. Distinguish the basic properties of all cells. Describe the differences between prokaryotic and eukaryotic cells. Specify the types of prokaryotic cells. Emphasize cell specialization as it relate...

Chapter 1: Introduction to Cell Biology  Outline the early history of Cell Biology. Distinguish the basic properties of all cells. Describe the differences between prokaryotic and eukaryotic cells. Specify the types of prokaryotic cells. Emphasize cell specialization as it relates to eukaryotic cells. Discuss the relevance of multicellularity and the significance of cellular differentiation. Review the dimensions important to Cell Biology. Clarify the structure and function of the different types of viruses. Define the mechanisms by which viral infections proceed. Explain the traits that distinguish viroid from viruses. Introduction Cells are the topic of intense study. The study of cells requires creative instruments and techniques. Cell biology is reductionist, based on the premise that studying the parts of the whole can explain the character of the whole.  THE DISCOVERY OF CELLS The discovery of cells followed from the invention of the microscope by Robert Hooke, and its refinement by Anton Leeuwenhoek. Cell theory was articulated in the mid-1800s by Schleiden, Schwann and Virchow. All organisms are composed of one or more cell. The cell is the structural unit of life. Cells arise from pre-existing cells by division. Basic Properties of Cells Life is the most basic property of cells. Cells can grow and reproduce in culture for extended periods. HeLa cells are cultured tumor cells isolated from a cancer patient (Henrietta Lacks) by George Gey in 1951. Cultured cells are an essential tool for cell biologists. HeLa: first human cells for extended culturing  HeLa is an immortal cell line used in scientific research. It is the oldest and most commonly used human cell line. The line is named after and derived from cervical cancer cells taken on February 8, 1951, from Henrietta Lacks, a 31-year- old African-American mother of five, who died of cancer on October 4, 1951. The immortality of HeLa cells contributed to their adoption across the world as the human cell line of choice for biomedical research. Though additional cells lines have been developed over the years, HeLa cells continue to be widely used to advance biomedical research and medicine. Basic Properties of Cells Cells Are Highly Complex and Organized Cellular processes are highly regulated. Cells from different species share similar structure, composition and metabolic features that have been conserved throughout evolution. Levels of cellular and molecular organization Basic Properties of Cells Cells Possess a Genetic Program and the Means to Use It Genes encode information to build each cell, and the organism. Genes encode information for cellular reproduction, activity, and structure. Basic Properties of Cells Cells Are Capable of Producing More of Themselves Cells reproduce, and each daughter cells receives a complete set of genetic instructions. Basic Properties of Cells Cells Acquire and Utilize Energy Photosynthesis provides fuel for all living organisms. Animal cells derive energy from the products of photosynthesis, mainly in the form of glucose. Cell can convert glucose into ATP—a substance with readily available energy. Basic Properties of Cells Cells Carry Out a Variety of Chemical Reactions Cells Engage in Mechanical Activities Cells Are Able to Respond to Stimuli Cells Are Capable of Self- Regulation Cells Evolve Basic Properties of Cells Cells Carry Out a Variety of Chemical Reactions Cells Engage in Mechanical Activities Cells Are Able to Respond to Stimuli Cells Are Capable of Self- Regulation Cells Evolve  Two Fundamentally Different Classes of Cells Prokaryotic and eukaryotic are distinguished by their size and type of organelles. Prokaryotes are all bacteria, which arose ~3.7 billion years ago. Eukaryotes include protists, animals, plants and fungi. Comparison: Prokaryotic & Eukaryotic Cells © 2013 John Wiley & Sons, Inc. All rights reserved. Comparison: Prokaryotic & Eukaryotic Cells © 2013 John Wiley & Sons, Inc. All rights reserved.  Basic Properties of Cells Characteristics that distinguish prokaryotic and eukaryotic cells Complexity: Prokaryotes are relatively simple; eukaryotes are more complex in structure and function. Cytoplasm: Eukaryotes have membrane-bound organelles and complex cytoskeletal proteins. Both have ribosomes but they differ in size. Cellular reproduction: Eukaryotes divide by mitosis; prokaryotes divide by simple fission. Locomotion: Eukaryotes use both cytoplasmic movement, and cilia and flagella; prokaryotes have flagella, but they differ in both form and mechanism. Genetic material: Packaging: Prokaryotes have a nucleoid region whereas eukaryotes have a membrane- bound nucleus. Amount: Eukaryotes have much more genetic material than prokaryotes. Form: Eukaryotes have many chromosomes made of both DNA and protein whereas prokaryotes have a single, circular DNA. © 2013 John Wiley & Sons, Inc. All rights reserved. The structure of cells Two Fundamentally Different Classes of Cells Prokaryotic and eukaryotic are distinguished by their size and type of organelles. Prokaryotes are all bacteria, which arose ~3.7 billion years ago. Eukaryotes include protists, animals, plants and fungi. Bio-geological clock: Proposed appearance time for major groups of organisms Eukaryotic cell structure: Epithelial cell from the male rat reproductive tract  Cytoplasm: A crowded compartment in a eukaryotic cell Colorized electron micrograph of a frozen single-celled eukaryote Cytoskeleton: Red Ribosomes: Green Cell membrane: Blue cytoskeleton is considered to be the backbone of a cell as it provides the cell its shape and structure. It is pivotal in controlling inter- and intracellular transportation and also plays an important role during cell division and differentiation Cytoskeleton is considered to be the backbone of a cell as it provides the cell its shape and structure. It is pivotal in controlling inter- and intracellular transportation and also plays an important role during cell division and differentiation Cellular reproduction: Eukaryotes and prokaryotes Cell division in eukaryotes Bacterial conjugation DNA (blue) and microtubules (green) of two daughter cells. Sharing of DNA through the F pilus Flagella: differences between prokaryotes and eukaryotes Basic Properties of Cells Types of Prokaryotic Cells Domain Archaea: Methanogens, Halophiles, Acidophiles, Thermophiles Domain Bacteria Includes the smallest known cells – mycoplasma Includes cyanobacteria – some photosynthetic bacteria Cyanobacteria gave rise to green plants and an oxygen-rich atmosphere. Some bacteria capable of nitrogen fixation. Figure 1.15 Cyanobacteria. (a) Electron micrograph of a cyanobacterium showing the cytoplasmic membranes that carry out photosynthesis. These concentric membranes are very similar to the thylakoid membranes present within the chloroplasts of plant cells, a reminder that chloroplasts evolved from a symbiotic cyanobacterium. (b) Cyanobacteria living inside the hairs of these polar bears are responsible for the unusual greenish color of their coats. (A: COURTESY OF NORMA J. LANG; B: COURTESY ZOOLOGICAL SOCIETY OF SAN DIEGO. Basic Properties of Cells Prokaryotic Diversity Prokaryotes are identified and classified on the basis of specific DNA sequences. Recent evidence indicates that prokaryotes are more diverse and numerous than previous thought. Basic Properties of Cells Types of Eukaryotic Cells: Cell Specialization Unicellular eukaryotes are complex single-celled organisms. Vorticella have a contractile ribbon in the stalk and a large macronucleus (arrow in figure) that contains multiple copies of its genes. Figure 1.16 Vorticella, a complex ciliated protist. A number of these unicellular organisms are seen here; most have withdrawn their “heads” due to shortening of the blue-stained contractile ribbon in the stalk. Each cell has a single large nucleus, called a macronucleus (arrow), which contains many copies of the genes. (CAROLINA BIOLOGICAL SUPPLY CO./PHOTOTAKE. Basic Properties of Cells Types of Eukaryotic Cells: Cell Specialization – Multicellular eukaryotes have different cell types for different functions. Differentiation occurs during embryonic development in other multicellular organisms. Numbers and arrangements of organelles relate to the function of the cell. Despite differentiation, cells have many features in common. Figure 1.17 Pathways of cell differentiation. A few of the types of differentiated cells present in a human fetus. (MICROGRAPHS COURTESY OF MICHAEL ROSS, UNIVERSITY OF FLORIDA. Basic Properties of Cells: Model Organisms  Basic Properties of Cells The Sizes of Cells and Their Components Cells are commonly measured in units of micrometers (1 μm = 10–6 meter) and nanometers (1 nm = 10–9 meter). Cell size is limited: By the volume of cytoplasm that can be supported by the genes in the nucleus. By the volume of cytoplasm that can be supported by exchange of nutrients. By the distance over which substances can efficiently travel through the cytoplasm via diffusion. Relative sizes of cells and cell components Synthetic Biology Synthetic Biology is a field oriented to create a living cell in the laboratory. A more modest goal is to develop novel life forms, beginning with existing organisms. Possible applications to medicine, industry, or the environment. Prospect is good after replacing the genome of one bacterium with that of a closely related species. Synthetic biology toolbox: Nucleic acids, proteins, and lipids © 2013 John Wiley & Sons, Inc. All rights reserved. The Human Perspective: The Prospect of Cell Replacement Therapy Stem cells are undifferentiated cells capable of self-renewal and differentiation. Adult stem cells can be used to replace damaged or diseased adult tissue. Hematopoietic stem cells can produce blood cells in bone marrow. Neural stem cells may be sued to treat neurodegenerative disorders. The Human Perspective: The Prospect of Cell Replacement Therapy Embryonic stem (ES) cells have even greater potential for differentiation (pluripotent) than adult stem cells. ES cells must be differentiated in vitro. The use of ES cells involves ethical considerations.  The Human Perspective: The Prospect of Cell Replacement Therapy Induced pluripotent (iPS) cells has been demonstrated in culture. Involves reprogramming a fully differentiated cell into a pluripotent stem cell. These cells have been used to correct certain disease conditions in experimental animals. Studies to reveal the mechanism of iPS could have significant medical applications. Steps taken to generate iPS for use in correcting the inherited disease sickle cell anemia in mice Viruses Viruses are pathogens. Viruses are intracellular obligate parasites. A virion is a virus particle outside the host cell. RNA-based Tobacco mosaic virus (TMV) Viral structure: Genetic material and can be single-stranded DNA or RNA. Protein capsid surrounds the genetic material. A lipid envelope may surround the capsid in some viruses. Viroids are pathogens, each consisting of a small, naked RNA molecule. Viroids cause disease by interfering with gene expression in host cells. Electron microscopy: TVM Viruses: Host infection diversity Virus and host Viruses have surface proteins that bind to the surface of the host cell. Viral specificity for a certain host is determined by the virus’ surface proteins. Viruses Viral infection types: Lytic infection: the virus redirects the host into making more virus particles, the host cell lyses and Bacteriophage infection of bacterium (late stage) releases the viruses. Integration: the virus integrates its DNA (called a provirus) into the host cell’s chromosomes. Infected host may behave normally until external stimulus activates provirus, leading to lysis. Host may give rise to viral progeny by budding. Host may become malignant. HIV infection of human lymphocyte (late stage) Experimental Pathways: The Origin of Eukaryotic Cells Prokaryotic cells arose first and gave rise to eukaryotic cells. Endosymbiont Theory: organelles in eukaryotic cells (mitochondria and chloroplasts) evolved from smaller prokaryotic cells.  Experimental Pathways: The Origin of Eukaryotic Cells Evidence to support endosymbiont theory Absence of eukaryote species with organelles in an intermediate stage of evolution. Many symbiotic relations are known among different organisms. Organelles of eukaryotic cells contain their own DNA. Nucleotide sequences of rRNAs from eukaryotic organelles resembled that of prokaryotes. Organelles duplicate independently of nucleus.