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Transcript
A Tour of the Cell Basics of Cells Plasma Membrane Forms external border Distinguishes cell from surroundings Cytoplasm Everything between plasma membrane and nucleus Typically known as fluid Organelles Play specific key roles in the lifecycle of cells Basics of Microscopes Light Microscope (LM) passes light through a specimen Typically is compound (two lenses) or simple (one lens) Electron Microscopes (EM) replaces the beam of light with one of electrons Specimen must be dead Held within a veritable vacuum Much more detailed- can see within cells, and under certain conditions individual atoms Types of Electron Microsopes Scanning (SEM) studies cell surfaces by passing electrons over the surface of a cell that has been coated with metal 3D images Transmission (TEM) studies the internal structures of cells by aiming electrons through a section of the cell Different Types of Microscopes Are Necessary for Different Sized Cells How they work Magnification: increase in the apparent size of an object Ocular is typically 10x Objectives are typically 4x, 10x, 40x, and 100x Total Magnification is ocular x objective Resolution: the measure of the clarity of an image Increases with the sophistication of the microscope Cell Theory ALL living things are composed of cells Schleiden and Schwann ALL cells come from other cells Biogenesis Virchow Cells are the most basic unit of life ?????????????????? Cell Size versus function Smallest are mycoplasmas (.1 to 1.0 micrometers) Muscle and nerve cells are longest (almost 1 meter in length!) Many fall somewhere between The Ratio of cell surface to cell volume that imposes upper limits on cell size Cell Size Regulation Prokaryotic Cells Bacteria and Archaea Cannot be seen with a low power microscope Lacks a nucleus instead compacts DNA into a nucleoid region Ribosomes in the cytoplasm detect messages from the DNA and assemble amino acids into polypeptides accordingly Surrounding those bacteria! Plasma Membrane encloses the cytoplasm Outside of the plasma membrane is a bacterial cell wall Protects Maintains shape Very Complex! Some have a capsule that surrounds the cell wall Help with attachment to surfaces/substrates Pili assist with attachment and sharing of genetic information Flagella assist with movement Not the same as eukaryotic flagella! Eukaryotic Cells are Compartmentalized! Endomembrane System Nucleus, Endoplasmic reticulum (ER), Golgi Apparatus (GA), Lysosomes, Peroxisomes, Vacuoles Work in the synthesis, storage, and export of important molecules Energy Converting Organelles Chloroplasts, Mitochondria Cytoskeleton Cilia, flagella Nucleus Genetic Control Center DNA fibers form into fibers of chromatin Each fiber contains a chromosome Surrounded by a nuclear envelope, perforated by nuclear pores Nucleolus in the center is responsible for producing ribosomes ER “network within the cell” ROUGH (RER) is dotted with ribosomes Produces membrane for use within the cell Produces proteins for export out of the cell Antibodies are a good example Releases these secretory proteins via transport vesicles for protection ER “network within the cell” SMOOTH (SER) is continuous with the RER, but lacks ribosomes Activity is a result of enzymes that are embedded within the membrane Synthesizes lipids, phospholipids and steroids in specific cells In the liver, SER assists with the breakdown of harmful substances and the regulation of blood sugar Can also store calcium ions- necessary for musculature ROUGH SMOOTH GA (The UPS of the Cell) Non-interconnected sacs of “pancakes” A varied resume: Molecular warehouse/finishing factory Receives and modifies products from the ER Ships out the secretory proteins from there Incorporates products that are made within the cell into the membranes and organelles that they are destined to become a part of Lysosomes and Peroxisomes Lysosomes contain digestive enzymes (produced in ER and GA) Protect cell by being enclosed in a membrane Engulf nutrients into food vacuoles- then fuse and digest them Destroy bacteria or other invaders Recycling center for damaged organelles Embryonic development… why we don’t have webbing Peroxisomes produce hydrogen peroxide and break it down into water and oxygen; also assist in the breakdown of various products Peroxisomes are SImilar Lysosomal Storage Diseases Missing a hydrolytic enzyme that is normally found in the lysosome Pompe’s disease: too much glycogen accumulates in the liver cells Tay-Sachs: lack a lipid digesting enzyme which allows the nervous system to be damaged due to an accumulation of lipids on the cells Deadly, though carriers can be detected Vacuoles Membranous sacs Central Vacuole in plants can contain a large lysosome, or help the cell to grow by absorbing water Typically store food, water and waste for the cell The Endomembrane System Chloroplasts Only found in photosynthetic organisms Plants and some protists Contain an inner and outer membrane Intermembrane space in between Fluid within the inner membrane is known as stroma Contain stacks of thylakoid disks, known as grana These are the actual sites where the chlorophyll traps solar energy Mitochondria Convert energy from one chemical form into another Carry out cellular respiration Food/Sugar ATP, the cell’s energy currency Also has an outer and an inner membrane Interior is a fluid area known as the mitochondrial matrix Where the chemical reactions of cellular respiration occur Heavily folded (folds = cristae) Folds increase surface area for C.R. Endosymbiosis Mitochondria and Chloroplasts resemble their own cells Double membranes Contain their own DNA Implication is that they were “cannibalized” by other cells Cytoskeleton Supportive network of fibers Microfilaments: mainly composed of actin Often assist with muscle contraction Microtubules: composed of tubulins Elongate(stretch) Provide anchorage for organelles A network of “railroad” tracks? Cilia and Flagella Cilia: short, numerous appendages Paramecium Flagella: longer, less numerous Euglena Both assist with movement Similar in physical structure to centrioles Involved with cellular division Comparing the 2 Cell Surfaces and Junctions Mostly for Support Cell junctions allow them to connect to each other Plasmodesmata form channels between cells so that they can interact appropriately as tissue Extracellular matrix holds the “tissue” together Tight junctions make a “leak-proof surface” <think stomach acid..> Anchoring Junctions hold cells loosely together so that substance scan still flow between them Communicating Junctions allow for cells to share necessary substances Connections Forming channels Thus, there are four main functional categories Manufacture: Breakdown: Energy Processing Support, Movement, and Communication Thus, there are four main functional categories Manufacture: Nucleus, Ribosomes, RER, SER, GA Breakdown: Lysosomes, Peroxisomes, Vacuoles Energy Processing Chloroplasts, Mitochondria Support, Movement, and Communication Cytoskeleton, Cell Walls, Extracellular Matrix, Cell Junctions Page… 67 Visit http://www.cellsalive.com