Chapter 1: Introduction to Cell Biology PDF

CHAPTER 1 Introduction to the Study of Cell Biology Required Reading: Karp – Chapter 1 You should read 1.4 for interest (not detail) and there are a few questions on Assignment 1 in Wiley Plus from it. You are not responsible for section 1.5 and 1.6)...

CHAPTER 1 Introduction to the Study of Cell Biology Required Reading: Karp – Chapter 1 You should read 1.4 for interest (not detail) and there are a few questions on Assignment 1 in Wiley Plus from it. You are not responsible for section 1.5 and 1.6) MBB 231 You ARE responsible for all other sections Remember that there is a glossary at the back of your book and on-line for each chapter and you should always be clear on the meaning of a word Remember to use the on-line resources; The Field of Cell Biology specificaly the glossary, flashcards, quizzes and practice questions. Also review the following animations – “The Scientific Method” and “Cell Structure” 1.1 Cells: the structural and function units of all living organisms Organ: a fully differentiated structural and functional unit in an animal that is specialized for some particular function Tissues: cells that aggregate to form a specific function Cell: The basic microscopic unit of all living beings; cell produces energy and uses it to build all the substances necessary for its life 1.2 The discovery of cells followed from the invention of the 1.1 | The Discovery of Cells microscope (1865) by Robert Hooke, and its refinement by Microscopy Anton Leewenhoek. Hooke termed the pores inside cork cells because they reminded him of the cells inhabited by monks living in a monastery. Leeuwenhoek was the first to examine a drop of pond water under the microscope and Hooke: double lens microscope observe the teeming microscopic “animalcules”(little animals) that darted back and forth. Leewenhoek: single lens microscope 1.3  1.1 | The Discovery of Cells Cell Theory The cell theory was articulated in the mid-1800s by: Matthias Schleiden, Theodor Schwann and Rudolf Virchow 1) All organisms are composed or one or more cells 2) The cell is the structural unit of life 3) Cells arise only by division from a pre-existing cell 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 and Martha Gey in 1951 Cultured cells are an essential tool for cell biologists 1.4  1.2 | Basic Properties of Cells Cells are Highly Complex and Organized Expanding The Cell Theory: Basic Properties of Cells Cells are highly complex and organized Cells possess a genetic program & the means to use it (a blueprint); encoded in collection of genes Cells are capable of producing more of themselves - mitosis and meiosis Cells acquire & utilize energy to develop & maintain complexity (photosynthesis and respiration) Cells carry out many chemical reactions – sum total of chemical reactions in cells = metabolism Cells engage in numerous mechanical activities Cells are able to respond to stimuli Cells are capable of self-regulation 1.5 Complexity of a cell: cell compartments 1.2 | Basic Properties of Cells Cells are Highly Complex and Organized Cells from different species share similar structure, composition and metabolic features that have been conserved throughout evolution 1.2 | Basic Properties of Cells Cells Possess a Genetic Program and the Means to Use It Organisms are built according to information encoded in a collection of genes Genes store information and constitute the blueprints for constructing cellular structures, the directions for running cellular activities, and the program for making more of themselves The molecular structure of genes allows for changes in genetic information (mutations) that lead to variation among individuals, which forms the basis of biological evolution All cells in an organism contain identical copies of DNA but become differentiated via development from a single fertilized egg 1.6 1.2 | Basic Properties of Cells Cells Are Capable of Producing More of Themselves Cells reproduce by division, a process in which the contents of a “mother” cell are distributed into two “daughter” cells Prior to division, the genetic material is faithfully duplicated, and each daughter cell receives a complete and equal share of genetic information Mammalian oocyte after unequal cell division to produce polar body (arrow) 1.7 1.2 | Basic Properties of Cells Cells Acquire and Utilize Energy Photosynthesis provides fuel for all living organisms Spirogyra: alga with ribbon-like chloroplast for photosynthesis Animal cells derive energy from the products of photosynthesis, mainly in the form of glucose Animal cells can convert glucose into ATP—a substance with readily available energy 1.8 1.2 | Basic Properties of Cells Cells Carry Out a Variety of Chemical Reactions Cells function like miniaturized chemical plants Virtually all chemical changes that take place in cells require enzymes to increase the rate at which a chemical reaction occurs The sum total of the chemical reactions in a cell represents that cell’s metabolism 1.9 1.2 | Basic Properties of Cells Cells Engage in Mechanical Activities Cells are very active, they can: transport materials, assemble and disassemble structures, and sometimes move itself from one site to another Activities are based on dynamic, mechanical changes within cells, many of which are initiated by changes in the shape of “motor” proteins Motor proteins are just one of many types of molecular “machines” used for mechanical activities 1.10 Lymphocyte homing  1.2 | Basic Properties of Cells Cells Are Able to Respond to Stimuli A single-celled can move away from an object in its path or toward nutrients Cells in plants or animals are covered with receptors that interact with substances in the environment Hormones, growth factors, extracellular materials, and substances on the surfaces of other cells can interact with these receptors Cells may respond to stimuli by altering their metabolism, moving from one place to another, or even committing suicide 1.11  1.2 | Basic Properties of Cells Self-regulated development in Cells Are Capable of Self-Regulation the sea urchin during normal (L) and cell Cells are robust and are protected separation from dangerous fluctuations in experiments (R) composition and behavior Feedback circuits serve to return the cell to the appropriate state Maintaining a complex, ordered state requires constant regulation Hans Driesch found that he could separate the first two or four cells of a sea urchin embryo and each of the isolated cells would proceed to develop into a normal embryo 1.12 1.2 | Basic Properties of Cells Cells Evolve How did cells arise? – we’ll probably never know Whereas the origin of cells is shrouded in near-total mystery, the evolution of cells can be studied by examining organisms that are alive today Cells share many features, including a common genetic code, a plasma Not considered the first life membrane, and ribosomes on earth but rather the only organism of its time still to According to a tenet of modern biology, all have living decendants living organisms evolved from a single, common ancestral cell that lived more than three billion years ago This ancient cell is often referred to as the last universal common ancestor (or LUCA) 1.13 1.3 | Characteristics that Distinguish Prokaryotic and Eukaryotic Cells Two basic classes of cells, prokaryotic and eukaryotic, are distinguished by their size and the types of organelles they contain Many basic differences and many similarities between the two types Because of their common ancestry, both types of cells share: an identical genetic language a common set of metabolic pathways many common structural features 1.14 1.3 | Characteristics that Distinguish Prokaryotic and Eukaryotic Cells There is a large section in chapter 1 of your text (1.3 and 1.4) that covers the difference between prokaryotic and eukaryotic cells Procaryotic cells were covered in your Biology courses This course focuses on mammalian eukaryotic cellular biochemistry and cell biology 1.15  Cells are differentiated in structure and in function Cells come in all shapes and sizes Form reflects Function (Morphology reflects Physiology) White blood cell (monocyte) with bacteria on cell surface All cells are made of the same type of chemical molecules 1.16  1.3 | Types of Eukaryotic Cells Model Organisms Escherichia coli (bacterium) Caenorhabditis elegans (nematode) Saccharomyces (yeast) Arabidopsis (mustard plant) Mus musculus (mouse) relatively simple organisms fast generation time large number of offspring Zebra fish easy to manipulate in the lab inexpensive to breed Drosophila (fruit fly) 1.17  1.3 | The Sizes of Cells and Their Components Relative sizes of cells and cell components Cells are commonly measured in units of micrometers (1 μm = 10–6 meter) and nanometers (1 nm = 10–9 meter). The cell size is limited: 1) By the volume of cytoplasm that can be supported by the genes in the nucleus. 2) By the volume of cytoplasm that can be supported by exchange of nutrients. 3) By the distance over which substances can efficiently travel through the cytoplasm via diffusion. However, some eukaryotic cells can be extremely large, as the green alga Acetabularia is more than 10 cm long. 1.18 1.3 | The Sizes of Cells and Their Components 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, Synthetic biology toolbox: industry, or the environment Nucleic acids, proteins, and lipids 1.19 How do we know what we know? “Facts” and the Scientific Method In science, “facts” are tenuous and dynamic The scientific method is used to assess new information – Scientists formulate a hypothesis (tentative explanation or model that can be tested) – Data are collected and interperted and the model is accepted or rejected Occam’s razor states that the simplest explanation consistent with the observations is most likely to be correct a principle urging one to select from among competing hypotheses that which makes the fewest assumptions 1.20 William of Occam (1285-1349)  How we explain observations? Hypothesis - statement consistent with most of the data, may take the form of a model (an explanation that appears to account for the data); must be testable Theory - a hypothesis that has been extensively tested by many investigators, using different approaches, widely accepted (example = cell theory) Law - a statement of fact of a natural phenomena that has been tested and confirmed over a long period of time with virtually no doubt of its validity (example = law of thermodynamics) Laws are most common in math and physics though in the Life Sciences there is “Mendal’s law of segregation” 1.21 Learning objectives for chapter 1 This was a very generalized chapter so you should focus on the big pictures presented as well as the following details: The three tenants of cell theory Fundamental differences between procaryotes and eukaryotes The advantages of model organisms (and what the common ones are) What limits cell size What is the scientific method Be able to identify a hypothesis, theory, law On the Wiley PLUS student companion site: View the following videos under biology basics animations “The Scientific Method” and “Cell Structure” and understand the quiz associated with these videos Make sure you are familiar with all the terms in the glossary and have done and understood: the WileyPlus Assignments for chapter 1 (Under Assignments) the Problem set for Chapter 1 (under Problem set in Modules) Canvas Assignment 1 (Under Assignments) 1.22