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Transcript
Cell Theory, Structure and Function 1 Introduction to Cells - Cells are the basic units of organisms - Cells can only be observed under microscope - Basic types of cells: Animal Cell Plant Cell Bacterial Cell 2 History of Cell Discovery • 1665: Robert Hooke observes cork, names tiny chambers CELLS • 1683: Anton van Leeuwenhoek discovers single-celled organisms • 1830-1855: Scientists discover cell nucleus, propose both animals and plants are made of cell • 1880-1890: Louis Pasteur & Robert Koch study bacteria 3 Cell Theory: 3 parts • All organisms are composed of one or more cells • The cell is the basic unit of organization of organisms • All cells come from preexisting cells 4 Number of Cells Organisms may be: • Unicellular – composed of one cell • Multicellularcomposed of many cells that may organize 5 Cells May be Prokaryotic or Eukaryotic Prokaryotes include bacteria & lack a nucleus or membrane-bound structures called organelles. Eukaryotes include most other cells & have a nucleus and membranebound organelles (plants, fungi, & animals). 6 Prokaryotes Nucleoid region contains the DNA •Cell membrane & cell wall • Contain ribosomes (no membrane) to make proteins in their cytoplasm 7 Eukaryotic Cell Contain 3 basic cell structures: • Nucleus • Cell Membrane • Cytoplasm with organelles 8 Two Main Types of Eukaryotic Cells Plant Cell Animal Cell 9 Organelles • Very small size • Can only be observed under a microscope • Have specific functions • Found throughout cytoplasm 10 Organelles Found in Cells Examples of Organelles include: • Endoplasmic reticulum (rough & smooth) – canals for movement • Golgi Bodies – wrap & export proteins • Nucleolus – makes ribosomes • Lysosomes – digests & gets rid of wastes • Ribosomes – makes proteins 11 Smooth & Rough Endoplasmic Reticulum Smooth ER lacks ribosomes & makes proteins USED IN the cell Rough ER has ribosomes on its surface & makes proteins to EXPORT 12 Golgi Bodies • Stacks of flattened sacs • Have a shipping side & a receiving side • Receive & modify proteins made by ER • Transport vesicles with modified proteins pinch off the ends Transport vesicle 13 Nucleolus • Cell may have 1 to 3 nucleoli • Inside nucleus • Disappears when cell divides • Makes ribosomes that make proteins 14 Lysosome • Contain digestive enzymes • Break down food and worn out cell parts for cells • Programmed for cell death (lyse & release enzymes to break down & recycle cell parts) 15 Mitochondria - Cell Powerhouse Mitochondrion ( mitochondria ) • Rod shape • Site of Cellular respiration 16 In Animal Cells: Mitochondria • Active cells like muscles have more mitochondria • Burn sugars to produce energy ATP 17 Surrounding the Cell: Cell Membrane Cell membrane - Lies immediately against the cell wall in plant cells - Made of protein and phospholipids (lipid bilayer) - Selectively permeable 18 Cell or Plasma Membrane Cell membrane - Living layer - Controls the movement of materials into and out of the cell 19 Cytoplasm of a Cell Cytoplasm - Jelly-like substance enclosed by cell membrane - Provides a medium for chemical reactions to take place 20 More on Cytoplasm Cytoplasm - Contains organelles to carry out specific jobs - Examples: chloroplast & mitochondrion 21 Control Organelle: Nucleus Nucleus - Controls the normal activities of the cell - Bounded by a nuclear membrane - Contains chromosomes 22 Nucleus - Each cell has fixed number of chromosomes that carry genes - Genes control cell characteristics 23 Plant Cell Organelles Chloroplast - Contains the green pigment chlorophyll - Traps sunlight to make sugars (food) - Process called photosynthesis 24 Plant Cell Cell wall - Dead layer - Large empty spaces present between cellulose fibers - Freely permeable 25 Plant Cell Cell wall - Made of cellulose, which forms very thin fibers - Strong and rigid - Found in plant cells 26 Plant Cell Cell wall - Protect and support the enclosed substances (protoplasm) - Resist entry of excess water into the cell - Give shape to the cell 27 Plant Cell Organelles Vacuole - Plant cells have a large central vacuole - Contains cell sap - Sugars, proteins, minerals, wastes, & pigments 28 Different kinds of plant cells Onion Epidermal Cells Guard Cells root hair Root Hair Cell 29 vacuole cytoplasm nucleus mitochondrion glycogen granule Animal cell - No cell wall or chloroplast - Stores glycogen in the cytoplasm for food energy cell membrane 30 Animal Cell Organelles • Near the nucleus • Paired structures • Help cell divide 31 Different kinds of animal cells white blood cell Amoeba red blood cell muscle cell cheek cells sperm nerve cell Paramecium 32 Similarities between plant cells and animal cells Both have a cell membrane surrounding the cytoplasm Both have a nucleus Both contain mitochondria 33 Differences between plant cells and animal cells Animal cells Plant cells Relatively smaller in size Relatively larger in size Irregular shape Regular shape No cell wall Cell wall present 34 Differences between Plant Cells and Animal Cells Animal cells Plant cells Vacuole small or absent Large central vacuole Glycogen as food storage Starch as food storage Nucleus at the center Nucleus near cell wall 35