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Chapter 7 Cells 1.1.1 and 1.1.2 Cell Theory All living things are made up of cells Cells are the basic unit of life New cells are made from existing cells Historical Background Improvements to microscope allowed the development of the cell theory since they could now see the cells Prominent scientists were: – Leeuwenhoek – Hooke – Brown – Schleiden – Virchow Ways to see the cells Compounds light microscope: living or dead, thin, stained for easy viewing, 1000 times magnification Electron microscope: dead, prepared ,1 million times magnification Dissecting microscope Ultracentrifuge: separates parts CELLS ALIVE ANIMATION http://www.cellsalive.com/cells/cell_model.ht m Organelles (little organs): Names and Functions Plasma Membrane or Cell Membrane: surrounds the entire cell and regulates the movement of materials or signals into and out of the cell. Cytoplasm: fluid environment between the nucleus and plasma membrane in which other organelles are suspended. This is where biochemical processes occur. Organelles: Names and Functions Nucleus: surrounded by nuclear membrane, contains DNA and directs cellular activities through expressing different genes. Nucleolus: in the nucleus, no membrane network synthesis of ribosomes. Where formation of ribosomes begins. Organelles: Names and Functions Endoplasmic Reticulum: interconnecting channels responsible for storage, synthesis, and transport of substances throughout the cell. Where lipid components of the membrane are put together. Also, where proteins and other materials are exported. – Two kinds Smooth ER: has no ribosomes Rough ER: has ribosomes Organelles: Names and Functions Ribosomes: site of protein synthesis, may be associated with the ER or located free in the cytoplasm Mitochondria: site of aerobic (with O) cellular respiration. This process makes ATP. ATP is aka adenosine triphosphate. This is cellular energy. Organelles: Names and Functions Golgi complex or Golgi apparatus: site of packaging and modification of proteins to be secreted. Lysosome: contains digestive enzymes that break down proteins or nucleic acids only at low pH. – How lysosomes work: http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapt er2/animation__lysosomes.html Organelles: Names and Functions Vacuole: membrane bound space containing water or other materials. – Food vacuoles are for digestion – Contractile vacuoles maintain water balance Organelles: Names and Functions Centriole: cylindrical structure which functions during cell division, these are common in animal cells but not in plants (Honors) Organelles: Names and Functions Chromatin: granular material in the nucleus Nuclear Pores: control flow in and out of nucleus to the cytoplasm Cilia: tiny hairs used for movement (Honors) Organelles: Names and Functions Cytoskeleton: how eukaryotic cells maintain their shape and gain support. – Microtubules: hollow structures make up of proteins known as tubulins. Help maintain shape, big part of cell division, because they form the spindle fibers Centrioles are located near the nucleus and help to organize cell division. -Microfilments: threadlike structures make up of protein called actin and help cells move. (Honors) Organelles: Names and Functions Peroxisomes: breaks down uric acid, amino acids and fatty acids. Works like a lysosome with a different set of materials. The break down of fatty acids gives energy to the cell Organelles: Names and Functions Found only in plants: – Chloroplasts: green pigment containing structure, the actual site of photosynthesis in plants. – Cell Wall: contains cellulose; surrounds and supports plant cells – Plasmodesmata: are narrow channels that act as intercellular cytoplasmic bridges to facilitate communication and transport of materials between plant cells Prokaryote vs Eukaryote Prokaryote – Usually smaller – No membrane bound organelles – DNA is not in a nucleus – Generally less complicated – Example: bacteria Prokaryote vs Eukaryote Eukaryote – Usually larger – More complex – Membrane bound organelles – Contain nucleus where DNA is stored, separately – Wide variety – Some are unicellular – Example: plants, animals, fungi, protists Cell boundaries Cell Membrane: – Main function: controls movement in and out of the cell Phosopholipid bilayer Called Fluid Mosaic Model – Just because it has so much stuff in it, it cannot be concretely identified Cell Membrane Contains: – Lipids – Protein molecules that are embedded in the lipid bilayer – Carbohydrate molecules are attached to many of these proteins some of the proteins form channels and pumps that help to move material across the cell membrane. Many of the carbohydrates act like chemical identification cards, allowing individual cells to identify one another. Cell boundaries Cell Wall – Main function: provide support and protect the plant cell made from fibers of carbohydrate and protein. – Made within the cell – Released from cell membrane – It is cellulose a carbohydrate fiber Active Art on Diffusion http://www.pearsonsuccessnet.com/snpapp/ iText/BrowseITEXTServlet?eventType=ope nIEXT&ISBNUrl=%2FiText%2Fproducts%2 F0-13-203512-X%2Findex.html&ISBN=013-203512-X&ITEXTOID=0-13-203512X&DisplayTitle=Biology+2008&TitleInFrame =Y&isbnUrlIsJavascript=false Diffusion Does not require energy Happens when random particles move from an area of higher concentration to an area of lower concentration through the cell membrane. General diffusion animation: – http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapt er2/animation__how_diffusion_works.html Osmosis Diffusion of water across a selectively permeable membrane Osmotic Pressure Isotonic: equal Hypotonic: too little (ions) Hypertonic: too much (ions) Facilitated Diffusion Diffusion of specific cell needs. Completed by a carrier protein to take particles in or out Requires no energy Animation – http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapt er2/animation__how_facilitated_diffusion_works .html Cell Boundaries Active versus Passive transport Active: requires energy Passive: does not require energy Active Transport Moves molecules with pumps across the concentration gradient – Exocytosis: EXITS the cell – Endocytosis: ENTERS the cell Endocytosis the process of taking material into the cell by means of infoldings, or pockets, of the cell membrane. The infolding makes a vacuole Large molecules, clumps of food, and even whole cells can be taken up in this way. Endocytosis Two types – phagocytosis Amoebas do it Take piece of food, form around it, make a vacuole – pinocytosis (py-nuh-sy-TOH-sis) Take water, form around it, make a vacuole Exocytosis How cells release large amounts of material from the cell Vacuole fuses with membrane Forces contents out – Example: contractile vacuoles remove water this way Cellular Diversity Unicellular vs Multicellular Unicellular Single cells can be an entire organism The meet the criteria for life Bacteria are living unicellular organisms Multicellular Cells throughout an organism can develop in different ways to perform different tasks This is called cells specialization Red blood cells in animals Stomata or guard cells in plants to regulate the influx of water