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Membrane Transport Cells need to move substances both in and out (of the cell) Cells need to move substances both in and out (of the cell) The transport.

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Presentation on theme: "Membrane Transport Cells need to move substances both in and out (of the cell) Cells need to move substances both in and out (of the cell) The transport."— Presentation transcript:

1 Membrane Transport Cells need to move substances both in and out (of the cell) Cells need to move substances both in and out (of the cell) The transport of water and other types of molecules across membranes is the key to many processes in living organisms The transport of water and other types of molecules across membranes is the key to many processes in living organisms Permeable membrane – allows substances through Permeable membrane – allows substances through Semi-permeable membrane (differentially permeable) – allow some substances through (smaller molecules such as H 2 O, CO 2, O 2 ), but not others (larger molecules) do not get through easily Semi-permeable membrane (differentially permeable) – allow some substances through (smaller molecules such as H 2 O, CO 2, O 2 ), but not others (larger molecules) do not get through easily

2 Passive transport – movement of substances that requires no energy (e.g. diffusion) Passive transport – movement of substances that requires no energy (e.g. diffusion) Diffusion – natural process where substances move from an area of high concentration to an area of low concentration (requires no energy) Diffusion – natural process where substances move from an area of high concentration to an area of low concentration (requires no energy) Eventually diffusion results in an equilibrium (even distribution of molecules throughout) Eventually diffusion results in an equilibrium (even distribution of molecules throughout) Osmosis – diffusion of water across a semi-permeable membrane. The direction of water movement (in or out of cell) depends on concentration of solute. Osmosis – diffusion of water across a semi-permeable membrane. The direction of water movement (in or out of cell) depends on concentration of solute. A solute (e.g. NaCl) is dissolved in a solvent (water) A solute (e.g. NaCl) is dissolved in a solvent (water) Passive Transport

3 Isotonic condition – concentration of solute and water inside cell EQUALS concentration of solute and water outside Isotonic condition – concentration of solute and water inside cell EQUALS concentration of solute and water outside Hypertonic condition - concentration of solute outside cell GREATER than solute concentration inside cell Hypertonic condition - concentration of solute outside cell GREATER than solute concentration inside cell Hypotonic condition - concentration of solute outside cell LESS than solute concentration inside cell Hypotonic condition - concentration of solute outside cell LESS than solute concentration inside cell Check it out: s/Osmosis.htm Check it out: s/Osmosis.htm s/Osmosis.htm s/Osmosis.htm bc.html bc.html bc.html bc.html tml tml tml tml

4 Active Transport Active transport – energy (from ATP) is needed to move substances from an area of low concentration to an area of high concentration (opposes diffusion) Active transport – energy (from ATP) is needed to move substances from an area of low concentration to an area of high concentration (opposes diffusion) Active transport is used to: Active transport is used to: 1. Generate charge gradients. For example in the mitochondrion, hydrogen ion pumps pump hydrogen ions into the intermembrane space of the organelle as part of making ATP. 1. Generate charge gradients. For example in the mitochondrion, hydrogen ion pumps pump hydrogen ions into the intermembrane space of the organelle as part of making ATP. 2. Concentrate ions, minerals and nutrients inside the cell that are in low concentration outside. 2. Concentrate ions, minerals and nutrients inside the cell that are in low concentration outside. 3. Keep unwanted ions or other molecules out of the cell that are able to diffuse through the cell membrane. 3. Keep unwanted ions or other molecules out of the cell that are able to diffuse through the cell membrane.

5 Movement of large molecules 2 important processes (require energy from ATP): 2 important processes (require energy from ATP): 1. Endocytosis – bringing in materials into cell a. pinocytosis – brings in liquid material pinocytosis b. phagocytosis - brings in solid material 2. Exocytosis – expel wastes and useful substances needed elsewhere, such as hormones or enzymes Exocytosis

6 Phagocytosis

7 Questions 18 & How have cell fractioning techniques and the use of radioisotopes helped advance the knowledge of cell biology? Cell fractionation allows for different cell parts to be separated so that study of the chemical reactions associated with each part can occur. Cell fractionation allows for different cell parts to be separated so that study of the chemical reactions associated with each part can occur. The use of radioisotopes allows scientists to follow chemicals in different chemical reactions as they occur in the cell organelles. The use of radioisotopes allows scientists to follow chemicals in different chemical reactions as they occur in the cell organelles. 19. In what ways does a cell membrane differ from a cell wall? The cell membrane acts as a boundary between the cell and its external environment. The cell membrane regulates the movement of molecular traffic into and out of a cell. Cell membranes are made of lipids and proteins. The cell membrane acts as a boundary between the cell and its external environment. The cell membrane regulates the movement of molecular traffic into and out of a cell. Cell membranes are made of lipids and proteins. Unlike cell membranes, cell walls are nonliving. Composed of cellulose, cell walls protect and support plant cells. Gases, water, and some minerals can pass through small pores in the cell wall, Cell walls are also found in prokaryotic cells. Animal cells do not have a cell wall. Unlike cell membranes, cell walls are nonliving. Composed of cellulose, cell walls protect and support plant cells. Gases, water, and some minerals can pass through small pores in the cell wall, Cell walls are also found in prokaryotic cells. Animal cells do not have a cell wall.

8 Questions 20 & Describe the structure of a cell membrane. A cell membrane is made up of two layers of lipids, with the water-soluble heads of these molecules facing the outer surface and inner surface of the cell. Embedded in the lipid bilayer are a variety of proteins. The proteins control the permeability of the cell membrane, act as receptor sites for hormones, and function to transport material in and out of the cell. A cell membrane is made up of two layers of lipids, with the water-soluble heads of these molecules facing the outer surface and inner surface of the cell. Embedded in the lipid bilayer are a variety of proteins. The proteins control the permeability of the cell membrane, act as receptor sites for hormones, and function to transport material in and out of the cell. 21. List three factors that alter diffusion rates. The concentration difference between the inside and outside of the cell (the greater the concentration differ ence, the greater the rate of diffusion); temperature (as temperature increases, the rate of diffusion increases); and pressure (the greater the pressure difference, the greater the rate of diffusion). The concentration difference between the inside and outside of the cell (the greater the concentration differ ence, the greater the rate of diffusion); temperature (as temperature increases, the rate of diffusion increases); and pressure (the greater the pressure difference, the greater the rate of diffusion).

9 Question Define isotonic, hypertonic, and hypotonic solutions. Isotonic solutions are solutions in which the concentration of solute molecules is equal to that inside the cell. Isotonic solutions are solutions in which the concentration of solute molecules is equal to that inside the cell. Hypotonic solutions are solutions in which the concentration of solute molecules is less than that inside the cell. Hypotonic solutions are solutions in which the concentration of solute molecules is less than that inside the cell. Hypertonic solutions are solutions in which the concentration of solute molecules is greater than that inside the cell. Hypertonic solutions are solutions in which the concentration of solute molecules is greater than that inside the cell.

10 Question How does facilitated diffusion differ from normal diffusion and osmosis? Diffusion, osmosis, and facilitated diffusion are forms of passive transport in which molecules move from an area of higher concentration to an area of lower concentration. Diffusion involves the passage of any molecules from a region of high concentration to a region of lower concentration. Osmosis refers to the diffusion of water molecules through a selectively permeable membrane. Diffusion, osmosis, and facilitated diffusion are forms of passive transport in which molecules move from an area of higher concentration to an area of lower concentration. Diffusion involves the passage of any molecules from a region of high concentration to a region of lower concentration. Osmosis refers to the diffusion of water molecules through a selectively permeable membrane. In facilitated diffusion, protein carrier molecules in the cell membrane transport molecules with the diffusion gradient at a much faster rate than is found with normal diffusion. In facilitated diffusion, protein carrier molecules in the cell membrane transport molecules with the diffusion gradient at a much faster rate than is found with normal diffusion.

11 Questions 24 & Why does grass wilt if it is over-fertilized? The concentration of solutes outside the grass leaves is greater than that inside the leaf cells and water is drawn from the leaves, causing the grass to wilt. The concentration of solutes outside the grass leaves is greater than that inside the leaf cells and water is drawn from the leaves, causing the grass to wilt. 25. How does passive transport differ from active transport? Passive transport occurs when solute molecules move with the diffusion gradient without the expenditure of energy. Active transport occurs when solute molecules move against the diffusion gradient. This process requires energy. Passive transport occurs when solute molecules move with the diffusion gradient without the expenditure of energy. Active transport occurs when solute molecules move against the diffusion gradient. This process requires energy.


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