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Transcript
7-3 Cell Boundaries Slide 1 of 47 Copyright Pearson Prentice Hall End Show 7-3 Cell Boundaries All cells are surrounded by a thin, flexible barrier known as the cell membrane. Many cells also produce a strong supporting layer around the membrane known as a cell wall. Slide 2 of 47 Copyright Pearson Prentice Hall End Show 7-3 Cell Boundaries Cell Membrane Cell Membrane The cell membrane regulates what enters and leaves the cell and also provides protection and support. Slide 3 of 47 Copyright Pearson Prentice Hall End Show Cell Membrane Cell Membrane Outside of cell Proteins Carbohydrate chains Cell membrane Inside of cell (cytoplasm) Protein channel Lipid bilayer Slide 4 of 47 Copyright Pearson Prentice Hall End Show 7-3 Cell Boundaries Cell Walls What is the main function of the cell wall? Slide 5 of 47 Copyright Pearson Prentice Hall End Show 7-3 Cell Boundaries Cell Walls Cell Wall Cell walls are found in plants, algae, fungi, and many prokaryotes. Slide 6 of 47 Copyright Pearson Prentice Hall 7-3 Cell Boundaries Diffusion Through Cell Boundaries Measuring Concentration A solution is a mixture of two or more substances. The substances dissolved in the solution are called solutes. The concentration of a solution is the mass of solute in a given volume of solution, or mass/volume. Slide 7 of 47 Copyright Pearson Prentice Hall 7-3 Cell Boundaries Diffusion Through Cell Boundaries What happens during diffusion? Slide 8 of 47 Copyright Pearson Prentice Hall End Show 7-3 Cell Boundaries Diffusion Through Cell Boundaries Diffusion Particles in a solution tend to move from an area where they are more concentrated to an area where they are less concentrated. This process is called diffusion. When the concentration of the solute is the same throughout a system, the system has reached equilibrium. Slide 9 of 47 Copyright Pearson Prentice Hall Diffusion Through Cell Boundaries Slide 10 of 47 Copyright Pearson Prentice Hall End Show Slide 11 of 47 Copyright Pearson Prentice Hall End Show 7-3 Cell Boundaries Osmosis What is osmosis? Slide 12 of 47 Copyright Pearson Prentice Hall End Show 7-3 Cell Boundaries Osmosis Osmosis Osmosis is the diffusion of water through a selectively permeable membrane. Copyright Pearson Prentice Hall Osmosis How Osmosis Works Dilute sugar solution (Water more concentrated) Concentrated sugar solution (Water less concentrated) Sugar molecules Selectively permeable membrane Copyright Pearson Prentice Hall Movement of water Slide 14 of 47 End Show Water tends to diffuse from a highly concentrated region to a less concentrated region. If you compare two solutions, three terms can be used to describe the concentrations: Hypertonic– surrounding solution is MORE concentrated than interior of cell – water moves out of the cell. • hypotonic - surrounding solution is LESS concentrated than interior of cell – water moves into of the cell • isotonic - surrounding solution is EQUALLY concentrated to the interior of cell – Water moves Slide 15 of 47 both in and out but no net gain or loss Copyright Pearson Prentice Hall End Show 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 16 Slide 16 of 47 End Show 7-3 Cell Boundaries Osmosis Osmotic Pressure Osmosis exerts a pressure known as osmotic pressure on the hypertonic side of a selectively permeable membrane. Slide 17 of 47 Copyright Pearson Prentice Hall 7-3 Cell Boundaries Cell in Isotonic Solution 10% NaCL 90% H2O ENVIRONMENT CELL 10% NaCL 90% H2O NO NET MOVEMEN T What is the direction of water movement? equilibrium The cell is at _______________. 18 Slide 18 of 47 7-3 Cell Boundaries Cell in Hypotonic Solution 10% NaCL 90% H2O CELL 20% NaCL 80% H2O What is the direction of water movement? 19 Slide 19 of 47 7-3 Cell Boundaries Cell in Hypertonic Solution 15% NaCL 85% H2O ENVIRONMENT CELL 5% NaCL 95% H2O What is the direction of water movement? 20 Slide 20 of 47 7-3 Cell Boundaries Cells in Solutions 21 Slide 21 of 47 7-3 Cell Boundaries Isotonic Solution NO NET MOVEMENT OF H2O (equal amounts entering & leaving) Hypotonic Solution CYTOLYSIS Hypertonic Solution PLASMOLYSIS 22 Slide 22 of 47 7-3 Cell Boundaries Cytolysis & Plasmolysis Cytolysis Plasmolysis 23 Slide 23 of 47 7-3 Cell Boundaries Osmosis in Red Blood Cells Isotonic Hypotonic Hypertonic 24 Slide 24 of 47 7-3 Cell Boundaries hypotonic hypertonic hypertonic isotonic isotonic hypotonic 25 Slide 25 of 47 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 26 Facilitated Diffusion Molecules will randomly move through the pores in Channel Proteins. 27 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. 28 Carrier Proteins • Other carrier proteins change shape to move materials across the cell membrane 29 7-3 Cell Boundaries Active Transport Active Transport Sometimes cells move materials in the opposite direction from which the materials would normally move—that is against a concentration difference. This process is known as active transport. Active transport requires energy. Slide 30 of 47 Copyright Pearson Prentice Hall 7-3 Cell Boundaries Active Transport Molecular Transport In active transport, small molecules and ions are carried across membranes by proteins in the membrane. Energy use in these systems enables cells to concentrate substances in a particular location, even when diffusion might move them in the opposite direction. Slide 31 of 47 Copyright Pearson Prentice Hall Active Transport Molecular Transport Molecule to be carried Active Transport Slide 32 of 47 Copyright Pearson Prentice Hall End Show Active Transport • Requires energy or ATP • Moves materials from LOW to HIGH concentration • AGAINST concentration gradient 33 Active transport Examples: Pumping Na+ (sodium ions) out and K+ (potassium ions) in against strong concentration gradients. Called Na+-K+ Pump 34 Sodium-Potassium Pump 3 Na+ pumped in for every 2 K+ pumped 35 out; creates a membrane potential 7-3 Cell Boundaries Active Transport Endocytosis and Exocytosis Endocytosis is the process of taking material into the cell. Two examples of endocytosis are: • phagocytosis • pinocytosis During exocytosis, materials are forced out of the cell. Slide 36 of 47 Copyright Pearson Prentice Hall Pinocytosis • Cell forms an invagination • Materials dissolve in water to be brought into cell • Called “Cell Drinking” 37 Phagocytosis - Capture of a Yeast Cell (yellow) by Membrane Extensions of an Immune System Cell (blue) 38 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 39 7-3 Click to Launch: Continue to: - or - Slide 40 of 47 End Show Copyright Pearson Prentice Hall 7-3 Unlike a cell wall, a cell membrane a. is composed of a lipid bilayer. b. provides rigid support for the surrounding cell. c. allows most small molecules and ions to pass through easily. d. is found only in plants, fungi, algae, and many prokaryotes. Slide 41 of 47 End Show Copyright Pearson Prentice Hall 7-3 The concentration of a solution is defined as the a. volume of solute in a given mass of solution. b. mass of solute in a given volume of solution. c. mass of solution in a given volume of solute. d. volume of solution in a given mass of solute. Slide 42 of 47 End Show Copyright Pearson Prentice Hall 7-3 If a substance is more highly concentrated outside the cell than inside the cell and the substance can move through the cell membrane, the substance will a. move by diffusion from inside the cell to outside. b. remain in high concentration outside the cell. c. move by diffusion from outside to inside the cell. d. cause water to enter the cell by osmosis. Slide 43 of 47 End Show Copyright Pearson Prentice Hall 7-3 The movement of materials in a cell against a concentration difference is called a. facilitated diffusion. b. active transport. c. osmosis. d. diffusion. Slide 44 of 47 End Show Copyright Pearson Prentice Hall 7-3 The process by which molecules diffuse across a membrane through protein channels is called a. active transport. b. endocytosis. c. facilitated diffusion. d. osmosis. Slide 45 of 47 End Show Copyright Pearson Prentice Hall