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Transcript
7-3 Cell Boundaries Slide 1 of 47 Copyright Pearson Prentice Hall End Show 7-3 Cell Boundaries 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 which maintains homeostasis and also provides protection and support for cells without a cell wall. Slide 3 of 47 Copyright Pearson Prentice Hall End Show 7-3 Cell Boundaries 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 7-3 Cell Boundaries Composition of Cell Membrane: 1. Lipid Bilayer: double layered sheet which is a flexible structure that forms a strong barrier between the cell and its surroundings Slide 5 of 47 Copyright Pearson Prentice Hall End Show 7-3 Cell Boundaries Phospholipids contain one phosphate group, one glycerol, and 2 fatty acids. Main component of cell membranes. Slide 6 of 47 Copyright Pearson Prentice Hall End Show 7-3 Cell Boundaries 7-3 Cell Boundaries Composition of Cell Membrane: 2. Protein molecules are embedded in the lipid bilayer. Carbohydrates attached to the proteins act like chemical identification cards allowing cells to identify each other. Some proteins form channels and pumps to help move material into and out of the cell Slide 7 of 47 Copyright Pearson Prentice Hall End Show 7-3 Cell Boundaries 3. Most cells are selectively permeable, meaning that some substances can pass across them and some cannot. Slide 8 of 47 Copyright Pearson Prentice Hall End Show 7-3 Cell Boundaries Cell Walls Cell Wall Cell walls are found in plants, algae, fungi, some protists and many prokaryotes. Slide 9 of 47 Copyright Pearson Prentice Hall End Show 7-3 Cell Boundaries • Cell walls have openings or pores to allow water, oxygen, carbon dioxide and other materials to pass through. They lie outside the cell membrane. They give structure and support – the thicker the cell wall the more stiff or rigid the structure will be. Slide 10 of 47 Copyright Pearson Prentice Hall End Show 7-3 Cell Boundaries Cell Walls What is the main function of the cell wall? Slide 11 of 47 Copyright Pearson Prentice Hall End Show 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 12 of 47 Copyright Pearson Prentice Hall End Show 7-3 Cell Boundaries Diffusion Through Cell Boundaries What happens during diffusion? - Molecules MOVE!!!! - Molecules are always in motion. They move around and bump into each other. Slide 13 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 inside the cell is the same as the concentration outside the cell, the cell and its environment has reached equilibrium. Slide 14 of 47 Copyright Pearson Prentice Hall End Show 7-3 Cell Boundaries Diffusion Through Cell Boundaries Slide 15 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. Whenever water moves, into or out of the cell, we call it osmosis. Slide 16 of 47 Copyright Pearson Prentice Hall End Show 7-3 Cell Boundaries Osmosis How Osmosis Works Dilute sugar solution (Water more concentrated) Concentrated sugar solution (Water less concentrated) Sugar molecules Selectively permeable membrane (only water can move) Copyright Pearson Prentice Hall Movement of water from high concentration Slide to low 17 of 47 concentration End Show 7-3 Cell Boundaries Osmosis In osmosis, water tends to diffuse from a highly concentrated region to a less concentrated region. If you compare solutions, three terms can be used to describe the concentrations of the solution due to the amount of solute dissolved in the water: - hypertonic (“above strength”)more solute/less water. - hypotonic (“below strength”)less solute/more water. - isotonic (”same strength”)same amount of solute Slide 18 of 47 Copyright Pearson Prentice Hall End Show 7-3 Cell Boundaries Osmosis Osmotic Pressure Osmosis exerts a pressure known as osmotic pressure on the cell compared to its environment. Remember both inside the cell and outside the cell there is a concentration. It is the water that moves!! Slide 19 of 47 Copyright Pearson Prentice Hall End Show 7-3 Cell Boundaries Osmosis What is osmosis? Slide 20 of 47 Copyright Pearson Prentice Hall End Show 7-3 Cell Boundaries Facilitated Diffusion Glucose molecules Facilitated Diffusion requires no energy because molecules still move from a higher to a lower High Concentration concentration. Each protein channel is specific for the type of molecule that it allows to enter the cell. Low Concentration Protein channel Copyright Pearson Prentice Hall Slide 21 of 47 End Show 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 22 of 47 Copyright Pearson Prentice Hall End Show 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 23 of 47 Copyright Pearson Prentice Hall End Show 7-3 Cell Boundaries Active Transport Molecular Transport Molecule to be carried Active Transport Slide 24 of 47 Copyright Pearson Prentice Hall End Show 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 (takes in food) • Pinocytosis (takes in water) Slide 25 of 47 Copyright Pearson Prentice Hall End Show 7-3 Cell Boundaries • During exocytosis, materials are forced out of the cell. • “Exo” = exit • “Cyto” = cell Slide 26 of 47 Copyright Pearson Prentice Hall End Show 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 27 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 28 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 29 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 30 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 31 of 47 End Show Copyright Pearson Prentice Hall