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Transcript
Chapter 3 Lecture PowerPoint Cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3.1: Introduction • The basic organizational structure of the human body is the cell. • There are 50-100 trillion cells in the human body. • Differentiation is when cells specialize. • As a result of differentiation, cells vary in size and shape due to their unique function. 2 3.2: A Composite Cell Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Phospholipid bilayer • Major parts include: • Nucleus • contains DNA • Cytoplasm • cellular contents between plasma membrane & nucleus • Cell membrane • selective barrier Flagellum Nucleus Chromatin Nuclear envelope Nucleolus Ribosomes Cell membrane Basal body Microtubules Rough Endoplasmic reticulum Centrioles Mitochondrion Smooth Endoplasmic reticulum Microvilli Secretory vesicles Cilia Golgi apparatus Microtubule Microtubules Lysosomes 3 Cell Membrane (aka Plasma Membrane) • • • • Outer limit of the cell Controls what moves in and out of the cell Selectively permeable Phospholipid bilayer • • • • Water-soluble “heads” form surfaces (hydrophilic) Water-insoluble “tails” form interior (hydrophobic) Permeable to lipid-soluble substances Cholesterol stabilizes the membrane 4 Cell Membrane Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Extracellular side of membrane Fibrous protein Glycolipid Carbohydrate Glycoprotein “Heads” of phospholipid Double layer of Phospholipid molecules “Tails” of phospholipid Cell membrane (a) Cell membrane (b) a: © Biophoto Associates/Photo Researchers, Inc. Cholesterol Globular molecules protein Cytoplasmic side of membrane Hydrophobic fatty acid “tail” Hydrophilic Phosphate “head” 5 Cytoplasm • Cytosol = water • Organelles = solids Cytoplasm is really like a Jello fruit salad where the Jello is the cytosol and the fruits (oranges, grapes, bananas, maybe walnuts, etc.) are the organelles. 6 Organelles Endoplasmic Reticulum (ER) • Connected, membrane-bound sacs, canals, and vesicles • Transport system • Rough ER Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Membranes Membranes • Studded with ribosomes • Smooth ER • Lipid synthesis • Added to proteins arriving from rough ER • Break down of drugs Ribosomes (b) (c) Ribosomes • Free floating or connected to ER • Provide structural support and enzyme activity to amino acids to form protein (protein synthesis) 7 Organelles Golgi apparatus • Stack of flattened, membranous sacs • Modifies, packages and delivers proteins Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Vesicles • Membranous sacs • Store substances Mitochondria • Membranous sacs with inner partitions • Generate energy Inner membrane Cristae Outer membrane (a) (b) a: © Bill Longcore/Photo Researchers, Inc. 8 Organelles Lysosomes • Enzyme-containing sacs • Digest worn out cell parts or unwanted substances Centrosome • Two rod-like centrioles • Used to produce cilia and flagella • Distributes chromosomes during cell division Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Peroxisomes • Enzyme-containing sacs • Break down organic molecules •Detoxifies alcohol Centriole (cross-section) Centriole (longitudinal section) (a) (b) a: © Don W. Fawcett/Visuals Unlimited 9 Organelles Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cilia • Short hair-like projections • Propel substances on cell surface Flagellum • Long tail-like projection • Provides motility to sperm (a) a: © Oliver Meckes/Photo Researchers, Inc. 10 © Colin Anderson/Brand X/CORBIS Organelles Microfilaments and microtubules • Thin rods and tubules • Support cytoplasm • Allows for movement of organelles Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Microtubules Microfilaments © M. Schliwa/Visuals Unlimited 11 Cell Nucleus Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. • Is the control center of the cell • Nuclear envelope • Porous double membrane • Separates nucleoplasm from cytoplasm • Nucleolus • Dense collection of RNA and proteins • Site of ribosome production Nucleus Nuclear envelope Nucleolus • Chromatin • Fibers of DNA and proteins • Stores information for synthesis of proteins Chromatin Nuclear pores (a) 12 3.3: Movements Into and Out of the Cell There are 2 ways substances move through the cell membrane. •Passive mechanisms do not require energy. • Simple diffusion • Facilitated diffusion • Osmosis • Filtration Active mechanisms require cell energy • Active transport • Endocytosis • Exocytosis • Transcytosis 13 Simple Diffusion •The process by which molecules or ions scatter or spread spontaneously from a higher concentration to a lower concentration • Oxygen and carbon dioxide can diffuse readily through the cell membrane •Equilibrium is reached. Solute molecule Permeable membrane A Water molecule B (1) A B (2) Time A B (3) 14 Animation: How Diffusion Works 15 Facilitated Diffusion • Substances that are not able to pass through the lipid bilayer need the help of membrane proteins to get across, this is called Facilitated Diffusion •Carrier molecules “revolving doors” are used to carry large molecules (transported substance) across the membrane. • Ex. Glucose and amino acids Region of higher concentration Transported substance Region of lower concentration Protein carrier molecule Cell membrane 16 Animation: How Facilitated Diffusion Works Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 17 Osmosis • The diffusion of water • Water moves toward a higher concentration of solutes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Selectively permeable membrane Protein molecule Water molecule A A B B (1) (2) Time 18 Animation: How Osmosis Works Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 19 Osmosis and Osmotic Pressure Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. • Osmotic Pressure – ability of osmosis to generate enough pressure to move a volume of water • Osmotic pressure increases as the concentration of nonpermeable solutes increases • Isotonic – same osmotic pressure • Hypertonic – higher osmotic pressure (water loss) • Hypotonic – lower osmotic pressure (water gain) (a) (b) (c) © David M. Phillips/Visuals Unlimited 20 Filtration • Smaller molecules are forced through porous membranes • Hydrostatic pressure important in the body • Molecules leaving blood capillaries Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Capillary wall Blood pressure Tissue fluid Blood flow Larger molecules Smaller molecules 21 Active Transport • The process that moves particles through membranes from regions of lower concentration to regions of higher concentration • Equilibrium is never reached. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Carrier protein Binding site Cell membrane Region of higher concentration Region of lower concentration Phospholipid molecules Transported particle (a) Carrier protein with altered shape Cellular energy (b) 22 Active Transport: Sodium-Potassium Pump • Active transport mechanism • Creates balance by “pumping” three (3) sodium (Na+) OUT and two (2) potassium (K+) INTO the cell • 3:2 ratio 23 QuickTime™ and a decompressor are needed to see this picture. 24 Endocytosis • Cell engulfs a substance by forming a vesicle around the substance • Three types: • Pinocytosis – substance is mostly water • Phagocytosis – substance is a solid • Receptor-mediated endocytosis – requires the substance to bind to a membrane-bound receptor Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cell Particle membrane Nucleus Nucleolus Phagocytized particle Vesicle 25 Endocytosis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cell Particle membrane Phagocytized particle Vesicle Nucleus Nucleolus Receptor-ligand combination Molecules outside cell Vesicle Receptor protein Cell membrane Cell membrane indenting Cytoplasm (a) (b) (c) 26 (d) Exocytosis • Reverse of endocytosis • Substances in a vesicle fuse with cell membrane • Contents released outside the cell • Release of neurotransmitters from nerve cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Endoplasmic reticulum Golgi apparatus Nucleus 27 Transcytosis • Endocytosis followed by exocytosis • Transports a substance rapidly through a cell • HIV crossing a cell layer Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. HIV-infected white blood cells Anal or vaginal canal Viruses bud HIV Receptor-mediated endocytosis Lining of anus or vagina (epithelial cells) Cell membrane Exocytosis Receptor-mediated endocytosis Virus infects white blood cells on other side of lining 28 3.4: The Cell Cycle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. • Series of changes a cell undergoes from the time it forms until the time it divide • Stages: • Interphase • Mitosis • Cytokinesis G2 phase S phase: genetic material replicates G1 phase cell growth Proceed to division Remain specialized Apoptosis Cytokinesis Restriction checkpoint 29 Interphase • Very active period • 3 Phases are involved Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. • During the G1 phase, the cell grows • During the S phase, the cell replicates DNA • During the G2 phase, Proceed to division the cell is in preparation for cell Remain specialized division G2 phase S phase: genetic material replicates Apoptosis G1 phase cell growth Cytokinesis Restriction checkpoint 30 Mitosis • Produces two daughter cells from an original somatic cell • Nucleus divides – karyokinesis • Cytoplasm divides – cytokinesis • Phases of nuclear division: • Prophase – chromosomes form; nuclear envelope disappears • Metaphase – chromosomes align midway between centrioles • Anaphase – chromosomes separate and move to centrioles • Telophase – chromatin forms; nuclear envelope 31 forms Mitosis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Late Interphase Cell has passed the restriction checkpoint and completed DNA replication, as well as replication of centrioles and mitochondria, and synthesis of extra membrane. (a) Early Interphase of daughter cells— a time of normal cell growth and function. Restriction checkpoint Nuclear envelope Chromatin fibers Centrioles Cleavage furrow Prophase Chromosomes condense and become visible. Nuclear envelope and nucleolus disperse. Spindle apparatus forms. Aster Microtubules (e) (b) Centromere Late prophase Spindle fiber Sister chromatids Chromosomes Nuclear envelopes Telophase and Cytokinesis Nuclear envelopes begin to reassemble around two daughter nuclei. Chromosomes decondense. Spindle disappears. Division of the cytoplasm into two cells. (d) (c) Mitosis Cytokinesis G1 phase Anaphase Sister chromatids separate to opposite poles of cell. Events begin which lead to cytokinesis. Metaphase Chromosomes align along equator, or metaphase plate of cell. © Ed Reschke S phase G2 phase Interphase 32 Animation: Mitosis and Cytokinesis Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 33 Cytoplasmic Division • Also known as cytokinesis • Begins during anaphase • Continues through telophase • Contractile ring pinches cytoplasm in half 34 Animation: Control of the Cell Cycle Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 35 3.5: Control of Cell Division • Cell division capacities vary greatly among cell types • Skin and blood cells divide often and continually • Neuron cells divide a specific number of times then cease • Chromosome tips (telomeres) that shorten with each mitosis provide a mitotic clock • Cells divide to provide a more favorable surface area to volume relationship • Growth factors and hormones stimulate cell division • Hormones stimulate mitosis of smooth muscle cells in uterus • Epidermal growth factor stimulates growth of new skin • Contact (density dependent) inhibition • Tumors are the consequence of a loss of cell cycle control 36 Tumors • Two types of tumors: • Benign – usually remains Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. localized • Malignant – invasive and Normal cells (with hairlike cilia) can metastasize; cancerous • Two major types of genes cause cancer: • Oncogenes – activate other genes that increase cell division Cancer cells • Tumor suppressor genes – normally regulate mitosis; if inactivated they are unable to regulate mitosis • Cells are now known as “immortal” © Tony Brain/Photo Researchers, Inc.; 37 Animation: How Tumor Suppressor Genes Block Cell Division Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 38 3.6: Stem and Progenitor Cells • Stem cell: • Can divide to form two new stem cells • Self-renewal • Can divide to form a stem cell and a progenitor cell • Totipotent – can give rise to every cell type • Pluripotent – can give rise to a restricted number of cell types • Progenitor cell: • Committed cell • Can divide to become any of a restricted number of cells • Pluripotent 39 Stem and Progenitor Cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sperm Sebaceous gland cell Egg Progenitor cell Progenitor cell Fertilized egg Skin cell Stem cell Progenitor cell Progenitor cell Stem cell Neuron Progenitor cell Progenitor cell Astrocyte Progenitor cell Progenitor cell Progenitor cell Bone cells Progenitor cell one or more steps Fibroblasts (a connective tissue cells) Blood cells and platelets produces another stem cell (self-renewal) 40 3.7: Cell Death Apoptosis: • Programmed cell death • Acts as a protective mechanism • Is a continuous process 41