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Cell Structure Chapter 7 1 2 • • • Cell Theory All organisms are composed of one or more cells. Cells are the smallest living units of all living organisms. Cells come from preexisting cells. 3 Prokaryote vs Eukaryote Cell Prokaryote – no nucleus - single loop of DNA - few organelles - bacteria Eukaryote – enclosed nucleus - DNA in chromosomes - many organelles 4 - plants, animals • Cell Size Most cells are relatively small because as size increases, volume increases much more rapidly. (surface area:volume) – longer diffusion time, less efficient 5 Visualizing Cells • Resolution - minimum distance two points can be apart and still be distinguished as two separate points – Compound microscopes - magnify in stages using multiple lenses – Transmission electron microscope electrons transmitted through specimen – Scanning electron microscope - electrons beamed onto surface of the specimen 6 Visualizing Cells 7 8 9 Cell Organelles • • Cytoplasm – a jelly-like substance that supports the organelles inside cell membrane encloses the cell contents – phospholipid bilayer with embedded proteins Phospholipid Membrane proteins 10 Nucleus • • • Contains genetic material (DNA) Directs activities of the cell – Nucleolus - region of RNA synthesis (needed for making proteins in the cell) Surface of nucleus bound by two nuclear membrane – Nuclear pores – protein gatekeepers – Usually proteins go in and RNA goes out 11 Nucleus 12 Chromosomes There is approximately 0.7 kg (1 ½ lbs) of DNA in your body! • • • • DNA of eukaryotes is densely packed into chromosomes. Each chromosome contains approximately 1 metre of DNA (if stretched out) There are 46 chromosomes in EVERY cell of your body! The DNA from all of your cells in your body stretched end to end would go from the Earth to the Sun 100 times! 13 Endoplasmic reticulum • • • Serves as system of channels from the nucleus Rough ER is “rough” because of ribosomes attached (sites of protein synthesis) Smooth ER – lack ribosomes – contain embedded enzymes which speed up the synthesis of carbohydrate and lipid molecules 14 15 Rough endoplasmic reticulum with ribosomes Electron micrograph of smooth endoplasmic reticulum 16 Golgi Apparatus – collection of Golgi bodies collect, package, and distribute molecules synthesized at one location in the cell and utilized at another location 17 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Golgi apparatus Proteins Transport vesicle Protein The golgi apparatus sorts and repackages molecules into vesicles that then travel to the cell membrane to be expelled 18 19 Lysosomes - - membrane-bound vesicles containing digestive enzymes – from Golgi apparatus The enzymes break down food particles and destroy old, worn-out cell parts 20 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cytoplasm Endoplasmic reticulum Phagocytosis Food vesicle Golgi apparatus Lysosomes Plasma membrane Extracellular fluid Digestion of phagocytized food particles or cells Transport vesicle Old or damaged organelle Breakdown of old organelle 21 Ribosomes – – site of protein synthesis assembled in nucleolus of cell 22 23 Mitochondria - contain 2 membranes (exterior and interior membranes) mitochondria convert glucose to usable energy for the cell (ATP) 24 Mitochondria 25 Mitochondria mitochondria line the flagellum of this cell A. "Powerhouse of the cell" - cellular metabolism B. Structure- outer and inner membranes – lots of surface are for maximum efficiency 26 Chloroplasts - Chloroplasts are larger and more complex than mitochondria - they are ONLY found in plant cells - they have special pigment molecules called CHLOROPHYLL that absorb sunlight and convert it into GLUCOSE 27 Cytoskeleton Network of protein fibers supporting cell shape and anchoring organelles – Actin filaments Microtubules cell movement – Microtubules Intermediate filaments Hollow tubes Facilitate cell movement – Intermediate filaments Stable - don’t break down Actin 28 Cytoskeleton 29 Plant Cells • Central vacuole – – • often found in the center of a plant, and serves as a storage facility for water and other materials It also provides some support for the cell because it is filled with water Cell wall - made of cellulose (long chains of glucose molecules) 30 Plant Cell Small green chloroplasts can be seen inside each plant cell 31 Plant cell 32 Animal Cells • Animal cells lack cell walls - these cells use a variety of proteins to provide support, strength, and resilience 33 Animal cells • The centriole - is found only in animal cells - it is located outside the nucleus and plays a role in cell division 34 The centriole is cylindrical and attaches spindle fibres to help pull chromosomes apart during cell division Electron micrograph of 2 centrioles inside a cell 35 36 CELLS • Watch the following video clip and try to identify the organelles inside the cell! 37 38 The Harvard Cell • http://multimedia.mcb.harvard.edu/ 39 What type of cell is this? cork cells 40 pollen grains 41 bone cells – growth plate 42 onion cells 43 human red blood cells 44 bacteria 45 brain cells 46 Neuromuscular junction – where nerve cells connect with muscle cells 47 moss cells 48 Sperm and egg - conception 49 blood clot 50 Hair cells in inner ear 51 rods and cones – cells of retina 52 tooth plaque – bacteria + food particles 53 basal cell carcinoma – skin cancer 54 brain cells 55 normal red blood cell ---------- sickled red blood cell 56 common cold virus 57 human immunodeficiency virus (HIV) 58 H1N1 virus (swine flu) 59