MCB 150 1nd Edition Lecture 2 Outline of Last Lecture I Course Staf II Required course materials III Optional Course Materials IV Additional Resources V Policies VI Grades Outline of Current Lecture VII Classification of cells VIII Domains of life IX Introduction to cells and molecules X Bacterial structure Current Lecture Classification of Cells The Linnaen system of classification Developed in the 1700s and was based on physical characteristics Genus Species Scheme classification of 2 kingdoms plants and animals that is still partially used but that isn t enough to explain microbes fungi bacteria etc 2 types of cells Eukaryotes cells that had a nucleus Prokaryotes cells without a nucleus Prokaryotic Cells Cell wall Rigid structure that contains and supports the cell usually but not always present Cytoplasmic membrane semipermeable membrane inside the cell wall Nucleoid Genetic material not surrounded by a membrane usually a single chromosome These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Eukaryotic Cells Animal cell used as an example Lacks a cell wall unless it s a plant cell Compartmentalization Distinct compartments inside of the cell called organelles Nucleus contains DNA and genetic materials encased in a membrane Domains of Life Before 1977 organisms were organized into 2 superkingdoms Prokaryotes without a nuclear membrane and membrane bound organelles Eukaryotes With a nuclear membrane and membrane bound organelles In 1997 at UIUC Carl Woese compared the sequences in diferent species of molecules rRNA Ribosomal RNA molecules were chosen to use as a basis for comparison for three reasons They are evolutionarily ancient They are found in all organisms They have the same functions in all organisms They are highly conserved meaning their sequences evolve slowly and are very similar Woese and his team concluded that there are actually two groups of prokaryotes Bacteria True bacteria that are found everywhere and in any environment o Nuclear membrane No o Membrane bound organelles No o Typical size 1 10 microns o Typical number shape of chromosomes 1 and mostly circular Archaea Considered ancient and frequently found in the extreme habitats heat pressure salts gases acidic or basic etc o Archaea are more closely related to eukaryotes than bacteria according to the rRNA comparison analysis o Membrane bound nucleus No o Membrane bound organelles No o Typical size 1 10 microns o Typical number shape 1 and mostly circular Eukarya o Nuclear membrane Yes o Membrane bound organelles Yes o Typical size 10 100 o Typical number shape more than 1 and mostly linear Intro to Cells Tenets of the Cell Theory Cells are the fundamental units of life All organisms are composed of one or more cells All cells come from preexisting cells Why do cells remain so small As the size of a single cell increases the surface area to volume ratio decreases meaning that as the cell grows the volume becomes too large to be able to export and import the nutrients and waste needed to power such a large cell through a membrane that has an insufficient surface area Resolution the ability to identify the separation of two objects that are close to each other Bacterial Structure All cells Some have a rigid cell wall that provides shape and protection Every cell is surrounded by a plasma membrane o Allows cells to maintain constant internal environment o Acts as a selectively permeable barrier o Is an interface for cells to send and receive info from surrounding cells Bacterial Most bacterial cells tend to be around the size of one micron The shaped however can vary from rod shaped to circular spiral etc Capsule thick mucous layer of complex carbohydrate and proteins that protects the cell from drying out and allowing it to stick to surfaces Non essential to the cells survival Inside the cell mostly cytoplasm ribosomes and genetic material Nucleoid area of the cytoplasm that contains the genetic material