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Basic Structure of a Cell 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 Number of Cells Organisms may be: • Unicellular – composed of one cell • Multicellularcomposed of many cells that may organize 3 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) 4 Prokaryotes Nucleoid region contains the DNA •Cell membrane & cell wall • Contain ribosomes (no membrane) to make proteins in their cytoplasm 5 Eukaryotic Cell Contain 3 basic cell structures: • Nucleus • Cell Membrane • Cytoplasm with organelles 6 Two Main Types of Eukaryotic Cells Plant Cell Animal Cell 7 Organelles Very small size Can only be observed under a microscope Have specific functions Found throughout cytoplasm 8 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 9 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 10 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) 11 Nucleolus • Cell may have 1 to 3 nucleoli • Inside nucleus • Disappears when cell divides • Makes ribosomes that make proteins 12 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 13 Cell Powerhouse Mitochondrion ( mitochondria ) Rod shape Site of Cellular respiration 14 In Animal Cells: Mitochondria Active cells like muscles have more mitochondria Burn sugars to produce energy ATP 15 Surrounding the Cell Cell membrane Lies immediately against the cell wall in plant cells Made of protein and phospholipids Selectively permeable 16 Cell or Plasma Membrane Cell membrane Living layer Controls the movement of materials into and out of the cell Selectively permeable 17 Cytoplasm of a Cell Cytoplasm Jelly-like substance enclosed by cell membrane Provides a medium for chemical reactions to take place 18 More on Cytoplasm Cytoplasm Contains organelles to carry out specific jobs Examples: chloroplast & mitochondrion 19 Control Organelle Nucleus Controls the normal activities of the cell Bounded by a nuclear membrane Contains chromosomes 20 More on the Nucleus Nucleus Each cell has fixed number of chromosomes that carry genes Genes control cell characteristics 21 Plant Cell Organelles Chloroplast Contain the green pigment chlorophyll Traps sunlight to make sugars (food) Process called photosynthesis 22 Plant Cell Cell wall Dead layer Large empty spaces present between cellulose fibers Freely permeable 23 Plant Cell Cell wall Made of cellulose which forms very thin fibers Strong and rigid Found in plant cells 24 Plant Cell Cell wall Protect and support the enclosed substances (protoplasm) Resist entry of excess water into the cell Give shape to the cell 25 Plant Cell Organelles Vacuole Have a large central vacuole Surrounded by tonoplast Contains cell sap Sugars, proteins, minerals, wastes, & pigments 26 Different kinds of plant cells Onion Epidermal Cells Guard Cells root hair Root Hair Cell 27 vacuole cytoplasm nucleus mitochondrion glycogen granule Animal cell No cell wall or chloroplast Stores glycogen in the cytoplasm for food energy cell membrane 28 Animal Cell Organelles • Near the nucleus • Paired structures • Help cell divide 29 Different kinds of animal cells white blood cell Amoeba red blood cell muscle cell cheek cells sperm nerve cell Paramecium 30 Similarities between plant cells and animal cells Both have a cell membrane surrounding the cytoplasm Both have a nucleus Both contain mitochondria 31 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 32 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 33 Compound Microscope • Instrument for observing small objects • Magnify images up to 2000X their size 34 Different parts of a microscope 35 Revolving nosepiece Eyepiece Clip Body tube Coarse adjustment Fine adjustment Condenser Arm Iris diaphragm Stage Objective Mirror Condenser control knob Base 36 The cell is the Basic Unit of Life • Cell is the smallest unit of living organisms • Unicellular organisms are made of one cell only • The cells of multicellular organisms are specialized to perform different functions – e.g. mesophyll cells for photosynthesis and root hair cells for water absorption 37 Levels of organization • Cells are grouped together and work as a whole to perform special functions 38 Tissue • A group of similar cells to perform a particular function – Animals : epithelial tissue, muscular tissue – Plants : vascular tissue, mesophyll 39 Organ • Different tissues group together to carry out specialized functions – Heart : consists of muscles, nervous tissue and blood vessels – Leaf : consists of epidermis, mesophyll and vascular tissue 40 The Structures of a Leaf (Plant Organ) Chloroplast Palisade Mesophyll Cell Spongy Mesophyll Cell Air Space Stoma 41 The Structures of a Heart (Animal Organ) 42 System • Several organs and tissues work together to carry out a particular set of functions in a co-ordinated way – Human : digestive, respiratory, excretory, circulatory and reproductive systems – Plant : root and shoot systems 43 Human Body Systems Examples of systems : Digestive System Respiratory System Circulatory System Nervous System Reproductive System 44 Examples of a Human Body System 45 Examples of a Human Body System The Respiratory System 46 Examples of a Human Body System Circulatory System 47 Examples of a Human Body System Nervous System 48 Levels of Organization CELLS (muscle cells,nerve cells) TISSUES (muscle, epithelium) ORGANS (heart, lungs, stomach) SYSTEMS (circulatory system) ORGANISM (human) 49 It’s You! 50 The Plasma Membrane - Gateway to the Cell 51 Photograph of a Cell Membrane 52 Cell Membrane The cell membrane is flexible and allows a unicellular organism to move 53 Homeostasis • Balanced internal condition of cells • Also called equilibrium • Maintained by plasma membrane controlling what enters & leaves the cell 54 Functions of Plasma Membrane Protective barrier Regulate transport in & out of cell (selectively permeable) Allow cell recognition Provide anchoring sites for filaments of cytoskeleton 55 Functions of Plasma Membrane Provide a binding site for enzymes Interlocking surfaces bind cells together (junctions) Contains the cytoplasm (fluid in cell) 56 Structure of the Cell Membrane 57 Membrane Components Phospholipids Cholesterol Proteins (peripheral and integral) Carbohydrates (glucose) 58 Phospholipids Make up the cell membrane Contains 2 fatty acid chains that are nonpolar Head is polar & contains a –PO4 group 59 FLUIDFluid MOSAIC MODEL mosaic model FLUID- because individual phospholipids and proteins can move around freely within the layer, like it’s a liquid. MOSAIC- because of the pattern produced by the scattered protein molecules when the membrane is viewed from above. 60 Cell Membrane Polar heads are hydrophilic “water loving” Nonpolar tails are hydrophobic “water fearing” Makes membrane “Selective” in what crosses 61 62 Cell Membrane The cell membrane is Hydrophobic made of 2 layers of molecules pass phospholipids called the easily; hydrophillic lipid bilayer DO NOT 63 Solubility • Materials that are soluble in lipids can pass through the cell membrane easily 64 Semipermeable Membrane Small molecules and larger hydrophobic molecules move through easily. e.g. O2, CO2, H2O 65 Semipermeable Membrane Ions, hydrophilic molecules larger than water, and large molecules such as proteins do not move through the membrane on their own. 66 Types of Transport Across Cell Membranes 67 Simple Diffusion • Requires NO energy • Molecules move from area of HIGH to LOW concentration 68 DIFFUSION Diffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural KINETIC ENERGY 69 Diffusion of Liquids 70 Diffusion through a Membrane Cell membrane Solute moves DOWN concentration gradient (HIGH to LOW) 71 Osmosis • Diffusion of water across a membrane • Moves from HIGH water potential (low solute) to LOW water potential (high solute) Diffusion across a membrane Semipermeable membrane 72 Diffusion of H2O Across A Membrane High H2O potential Low solute concentration Low H2O potential High solute concentration73 Cell in Isotonic Solution 10% NaCL 90% H2O ENVIRONMENT CELL 10% NaCL 90% H2O NO NET MOVEMENT What is the direction of water movement? equilibrium The cell is at _______________. 74 Cell in Hypotonic Solution 10% NaCL 90% H2O CELL 20% NaCL 80% H2O What is the direction of water movement? 75 Cell in Hypertonic Solution 15% NaCL 85% H2O ENVIRONMENT CELL 5% NaCL 95% H2O What is the direction of water movement? 76 Cells in Solutions 77 Isotonic Solution NO NET MOVEMENT OF H2O (equal amounts entering & leaving) Hypotonic Solution CYTOLYSIS Hypertonic Solution PLASMOLYSIS 78 Cytolysis & Plasmolysis Cytolysis Plasmolysis 79 Osmosis in Red Blood Cells Isotonic Hypotonic Hypertonic 80 hypotonic hypertonic hypertonic isotonic isotonic hypotonic 81 Three Forms of Transport Across the Membrane 82 Passive Transport Simple Diffusion Doesn’t require energy Moves high to low concentration Example: Oxygen or water diffusing into a cell and carbon dioxide diffusing out. 83 Passive Transport Facilitated diffusion Doesn’t require energy Uses transport proteins to move high to low concentration Examples: Glucose or amino acids moving from blood into a cell. 84 Proteins Are Critical to Membrane Function 85 Types of Transport Proteins • Channel proteins are embedded in the cell membrane & have a pore for materials to cross • Carrier proteins can change shape to move material from one side of the membrane to the other 86 Facilitated Diffusion Molecules will randomly move through the pores in Channel Proteins. 87 Facilitated Diffusion • Some Carrier proteins do not extend through the membrane. • They bond and drag molecules through the lipid bilayer and release them on the opposite side. 88 Carrier Proteins • Other carrier proteins change shape to move materials across the cell membrane 89 Active Transport Requires energy or ATP Moves materials from LOW to HIGH concentration AGAINST concentration gradient 90 Active transport Examples: Pumping Na+ (sodium ions) out and K+ (potassium ions) in against strong concentration gradients. Called Na+-K+ Pump 91 Sodium-Potassium Pump 3 Na+ pumped in for every 2 K+ pumped out; creates a membrane potential 92 Moving the “Big Stuff” Exocytosis - moving things out. Molecules are moved out of the cell by vesicles that fuse with the plasma membrane. This is how many hormones are secreted and how nerve 93 cells communicate with one another. Exocytosis Exocytic vesicle immediately after fusion with plasma membrane. 94 Moving the “Big Stuff” Large molecules move materials into the cell by one of three forms of endocytosis. 95 Pinocytosis Most common form of endocytosis. Takes in dissolved molecules as a vesicle. 96 Pinocytosis • Cell forms an invagination • Materials dissolve in water to be brought into cell • Called “Cell Drinking” 97 Example of Pinocytosis pinocytic vesicles forming mature transport vesicle Transport across a capillary cell (blue). 98 Receptor-Mediated Endocytosis Some integral proteins have receptors on their surface to recognize & take in hormones, cholesterol, etc. 99 Receptor-Mediated Endocytosis 100 Endocytosis – Phagocytosis Used to engulf large particles such as food, bacteria, etc. into vesicles Called “Cell Eating” 101 Phagocytosis About to Occur 102 Phagocytosis - Capture of a Yeast Cell (yellow) by Membrane Extensions of an Immune System Cell (blue) 103 Exocytosis The opposite of endocytosis is exocytosis. Large molecules that are manufactured in the cell are released through the cell membrane. Inside Cell Cell environment 104 Videos • Click a hyperlink to choose a video. • Diffusion • Osmosis • Passive Transport • Active Transport • Endocytosis and Exocytosis Video Video 1 Diffusion • Click the image to play the video segment. Video 2 Osmosis • Click the image to play the video segment. Video 3 Passive Transport • Click the image to play the video segment. Video 4 Active Transport • Click the image to play the video segment. Video 5 Endocytosis and Exocytosis • Click the image to play the video segment.