The Cell Chapter 2

Human Anatomy, 3rd edition Introduction Cell – structural and functional unit of an organism Sizes vary Two subdivisions Cell membrane Cytoplasm Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Cell Membrane Structure Lipid bilayer Proteins float among the phospholipids Molecules are constantly moving Fluid mosaic model Functions Encloses components Boundary through which substances enter or exit Selectively permeable Human Anatomy, 3rd edition Prentice Hall, © 2001

Membrane Transport Passive processes Active processes Molecules spread from an area of greater concentration to an area of lower concentration Do not use cellular energy Active processes Molecules move from an area of lower concentration to an area of greater concentration Use cellular energy From high energy bonds of ATP

Passive Transport Processes Diffusion Osmosis Facilitated diffusion Filtration

Diffusion Molecules move from an area of high concentration to an area of low concentration until they are uniformly distributed http://www.okc.cc.ok.us/biologylabs/Documents/Cells%20Membranes/Diffusion_Definition.htm

Osmosis Water molecules move from an area of lower solute concentration to higher solute concentration through a semipermeable membrane http://www.biologycorner.com/bio1/diffusion.html

Facilitated Diffusion Molecules move across a membrane with the aid of a carrier protein Human Anatomy, 3rd edition Prentice Hall, © 2001

Filtration Molecules are forced through membranes by mechanical pressure http://clem.mscd.edu/~raoa/bio2320/uriphys/sld003.htm

Active Transport Processes Ion pumps Endocytosis Exocytosis

Ion Pumps Molecule attaches to a carrier protein in the membrane The molecule moves through the protein from low concentration to high concentration

Endocytosis & Exocytosis Materials move into the cell by their inclusion into vesicles Phagocytosis Pinocytosis Exocytosis Materials move out of the cell Cellular secretion Human Anatomy, 3rd edition Prentice Hall, © 2001

Inside the Cell Membrane Cytoplasm Cytosol Thick fluid Contains suspended particles Organelles Specific functions Human Anatomy, 3rd edition Prentice Hall, © 2001

Cytoplasm Contents Function Mostly water Substance in which chemical reactions occur Packages chemicals Excretion of waste materials

Organelles Perform specific functions necessary for cell structure, maintenance, and metabolism Membranous or nonmembranous

Membranous Organelles

Human Anatomy, 3rd edition Nucleus “Control Center” DNA Nuclear Envelope Nuclear pores Nucleolus Composed of RNA Manufactures ribosomes Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Chromatin Human Anatomy, 3rd edition Prentice Hall, © 2001

Endoplasmic Reticulum (ER) Network of channels running through the cytoplasm Functions Surface for chemical reactions Transport Storage Secretion Rough ER Smooth ER Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Golgi Apparatus Located near the nucleus Associated with ER Human Anatomy, 3rd edition Prentice Hall, © 2001

Function of the Golgi Apparatus Packaging and secretion of Proteins, Carbohydrates Lipids FG02_18.JPG Title: The Function of the Golgi Apparatus Notes: (a) This diagram shows the functional link between the ER and the Golgi apparatus. Transport vesicles shuttle secretory product from the ER to the Golgi, and transfer vesicles move material between Golgi saccules. (b)Exocytosis at the cell surface. Keywords: Golgi, ER, endoplasmic reticulum, transport vesicles, secretory vesicles, transfer vesicles, saccules, maturing face, lysosomes, exocytosis, membrane protein Human Anatomy, 3rd edition Prentice Hall, © 2001

Lysosomes “Suicide packets” Produced by Golgi Apparatus Contain digestive enzymes Defense against disease Break down cellular debris Recycling of useful molecules in the cell

Human Anatomy, 3rd edition Mitochondria “Powerhouse” of the cell Production of ATP Double walled Cristae Matrix mtDNA Inherited from the mother Human Anatomy, 3rd edition Prentice Hall, © 2001

Nonmembranous Organelles

Human Anatomy, 3rd edition Cytoskeleton Protein framework Microfilaments Microtubules Intermediate filaments Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Cilia Projections of cell membrane Short, many Formed from microtubules Cause currents at cell surface Move substances along surface of cell or move entire cell Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Flagella Projections of cell membrane Few, long Cause currents at cell surface Move entire cell Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Ribosomes Attached to rough ER Scattered throughout cytoplasm Sites of protein synthesis Receive messages from RNA Assembly of amino acids into proteins Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Centrioles Near nucleus 9 bundles of microtubules Function in cell reproduction Human Anatomy, 3rd edition Prentice Hall, © 2001

Intercellular Attachments FG02_20A.JPG Title: Cell Attachments Notes: (a)Diagrammatic view of an epithelial cell, showing the major types of intercellular connections. Keywords: epithelial cell, intercellular connections, tight junction, belt desmosome, terminal web, button desmosome, gap junctions Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Gap Junctions Binding of membrane proteins hold cells together Allow small molecules to pass through Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Tight Junctions Partial fusion of the lipid parts of adjacent cell membranes hold cells together Block water and solutes Human Anatomy, 3rd edition Prentice Hall, © 2001

Human Anatomy, 3rd edition Desmosomes Layer of proteoglycan and intermediate filaments hold cells together Dense area binds to the cytoskeleton Very strong, resist stretching and twisting Human Anatomy, 3rd edition Prentice Hall, © 2001

Extracellular Materials Body fluids Interstitial fluids Plasma Secreted inclusions Substances forming matrix

Cells and Aging Physical signs Physiological signs Extracellular characteristics Immunology

Cell Growth and Replacement Cell division Mitosis Occurs in somatic cells Results in diploid cells Meiosis Occurs in reproductive cells Results in haploid cells