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UIUC MCB 150 - Introduction to cells

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MCB 150 1nd Edition Lecture 2Outline of Last Lecture I.Course StafII. Required course materialsIII. Optional Course MaterialsIV. Additional ResourcesV. PoliciesVI. GradesOutline of Current Lecture VII. Classification of cellsVIII. Domains of lifeIX. Introduction to cells and moleculesX. Bacterial structureCurrent LectureClassification of CellsThe 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 nucleusProkaryotic 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 membraneDomains 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 organellesIn 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: Noo Membrane bound organelles: Noo Typical size: 1-10 micronso 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 analysiso Membrane bound nucleus: Noo Membrane bound organelles: Noo Typical size: 1-10 micronso Typical number/shape: 1 and mostly circular- Eukarya:o Nuclear membrane: Yeso Membrane bound organelles: Yeso Typical size: 10-100o Typical number/shape: more than 1 and mostly linear. Intro to CellsTenets 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 cellsWhy 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 otherBacterial 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 environmento Acts as a selectively permeable barriero Is an interface for cells to send and receive info from surrounding cellsBacterial:- 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 cellfrom 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


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UIUC MCB 150 - Introduction to cells

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