Diffusion, hypertonic, hypotonic, isotonic Biology Cell Membrane: Diffusion, hypertonic, hypotonic, isotonic MT: Cell Processes Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 7-3 Cell Boundaries 7-3 Cell Boundaries Photo Credit: © Quest/Science Photo Library/Photo Researchers, Inc. What surrounds a cell? A cell membrane! Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Cell Membrane All cells are surrounded by a thin, flexible barrier known as the cell membrane. Outside of cell Carbohydrate chains Proteins Cell membrane The cell membrane regulates what enters and leaves the cell. Inside of cell (cytoplasm) Protein channel Lipid bilayer Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Cell Membrane What is the main function of the cell membrane? Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Cell Membrane Cell Membrane 1. Regulates what enters and leaves the cell 2. Provides protection and support Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Cell Membrane The composition of nearly all cell membranes is a double-layered sheet called a phospholipid bilayer. The cell membrane regulates what enters and leaves the cell. Phospholipid bilayer Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Cell Membrane The cell membrane is: *Semi-permeable: only certain substances are let into/out of the cell. Usually small substances. Ex: Strainer: water is let through but the beans/noodles are not Ex: Window Screen: air and small bugs are let in but big bugs are not Copyright Pearson Prentice Hall

Diffusion Through Cell Boundaries - is the movement of substances across the cell membrane. Copyright Pearson Prentice Hall

Diffusion Through Cell Boundaries What happens during diffusion? Copyright Pearson Prentice Hall

Diffusion Through Cell Boundaries Particles move from an area of HIGH concentration to an area of LOW concentration. When particles are balanced on both sides of the membrane, the system has reached equilibrium. Copyright Pearson Prentice Hall

Diffusion Through Cell Boundaries Diffusion is the process by which molecules of a substance move from areas of higher concentration to areas of lower concentration. Diffusion does not require the cell to use energy. Copyright Pearson Prentice Hall

Diffusion Through Cell Boundaries There is a higher concentration of solute on one side of the membrane as compared to the other side of the membrane. Diffusion is the process by which molecules of a substance move from areas of higher concentration to areas of lower concentration. Diffusion does not require the cell to use energy. Copyright Pearson Prentice Hall

Diffusion Through Cell Boundaries Particles move from the side of the membrane with a HIGH concentration of solute to the side of the membrane with a LOW concentration of solute until EQUILIBRIUM is reached. Diffusion is the process by which molecules of a substance move from areas of higher concentration to areas of lower concentration. Diffusion does not require the cell to use energy. Copyright Pearson Prentice Hall

Diffusion Through Cell Boundaries When equilibrium is reached, solute particles continue to diffuse across the membrane in both directions but with a net movement of zero. Diffusion is the process by which molecules of a substance move from areas of higher concentration to areas of lower concentration. Diffusion does not require the cell to use energy. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Osmosis What is osmosis? Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Osmosis Osmosis Osmosis is the diffusion of water through a membrane. Copyright Pearson Prentice Hall

Selectively permeable membrane Osmosis How Osmosis Works Dilute sugar solution (Water more concentrated) Concentrated sugar solution (Water less concentrated) Sugar molecules Osmosis is the diffusion of water through a selectively permeable membrane. In the first beaker, water is more concentrated on the right side of the membrane. As a result, the water diffuses (as shown in the second beaker) to the area of lower concentration. Movement of water Selectively permeable membrane Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Osmosis Water tends to diffuse from a HIGH concentration region to a LOW concentration region. hypertonic (“above strength”): more particles than the other side hypotonic (“below strength”): less particles than the other side Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Osmosis When concentrations of solutions are the same on both sides of a membrane, the solutions are isotonic (”same strength”). Copyright Pearson Prentice Hall