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Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
Chapter 5 - Cell Transport
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Chapter 5 - Cell Transport

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  • The Plasma Membrane 12/16/12 G. Podgorski, Biol. 1010
  • The Plasma Membrane 12/16/12 G. Podgorski, Biol. 1010
  • The Plasma Membrane 12/16/12 G. Podgorski, Biol. 1010
  • The Plasma Membrane 12/16/12 G. Podgorski, Biol. 1010
  • The Plasma Membrane 12/16/12 G. Podgorski, Biol. 1010
  • The Plasma Membrane 12/16/12 G. Podgorski, Biol. 1010
  • The Plasma Membrane 12/16/12 G. Podgorski, Biol. 1010
  • The Plasma Membrane 12/16/12 G. Podgorski, Biol. 1010
  • The Plasma Membrane 12/16/12 G. Podgorski, Biol. 1010
  • The Plasma Membrane 12/16/12 G. Podgorski, Biol. 1010
  • Transcript

    • 1. CH T R 5 AP EHomeostasis and Cell Transport
    • 2. Homeostasis• Homeostasis: the biological balance between a cell or an organism and its environment. − Cell membranes help organisms maintain homeostasis by controlling what substances may enter or leave cells.
    • 3. Structure of the Cell Membrane
    • 4. Membrane Components• Phospholipids • Proteins• Cholesterol (peripheral and integral) • Carbohydrates (glucose)
    • 5. Phospholipids• Pictured here is a phospholipid, which is the lipid that makes up the cell membrane and the membranes of cell organelles.• It consists of a polar head and two non-polar tails. Phospholipids differ from triglycerides because they have 2 fatty acids instead of 3. =
    • 6. Phospholipids• Phospholipidheads arehydrophilic, orwater-loving, sothey want to benear the water.The fatty acidsare hydrophobic,or water-fearing,so they orientthemselves awayfrom water.
    • 7. FLUID MOSAIC MODEL• FLUID- because individual phospholipids and proteins can move side-to-side 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.
    • 8. Selectively Permeable Membrane• The cell membrane is selectively permeable,because it allows some things but not all thingsto pass through it. Molecules like O2, CO2 andH2O move easily across the membrane.• Ions, hydrophilic molecules larger thanwater, and large molecules such as proteins donot move through the membrane on their own.
    • 9. Passive Transport• In Passive Transport, substances cross the cell membrane with NO energy input from the cell.• The simplest type of passive transport is diffusion.
    • 10. Diffusion• Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration. − Concentration Gradient - the difference in the concentration of molecules across a distance. − Molecules tend to move from where they are more concentrated to where they are less concentrated (“down” their concentration gradient). − Concentration Gradient
    • 11. Diffusion• Diffusion is driven entirely by the molecules’ kinetic energy. − Molecules are in constant motion.• Diffusion will eventually cause the molecules to be in equilibrium – the concentration of molecules will be the same throughout the space the molecules occupy. − At equilibrium, molecules continue to move, but their movements are in different directions and “cancel” each other out!• How Diffusion Works
    • 12. Diffusion
    • 13. Diffusion
    • 14. Diffusion
    • 15. Diffusion Across Membranes• Diffusion across a membrane is also called simple diffusion.• Remember though that cell membranes are selectively permeable - some substances can move in and out easily, but others cannot. − The diffusion of a molecule across the cell membrane depends on:  Size of molecule  Type of molecule  Chemical nature of the membrane
    • 16. Diffusion Across Membranes Diffusion across a membrane Selectively Permeable Membrane
    • 17. Diffusion Across Membranes
    • 18. Osmosis• Osmosis is a special type of diffusion. Osmosis is the diffusion of water across a membrane.• In osmosis, ONLY water is moving.• In order to understand osmosis, we need to have a little review of solutions: − solute = substance dissolved in the solution ex. salt − solvent = substance that dissolves another substance ex. water
    • 19. OsmosisWater molecules diffuse across a cell membrane from an area of higher concentration to an area of lower concentration.
    • 20. Direction of Osmosis • The overall movement of water is determined by the concentration of solutes on either side of the membrane.High H2O Low H2Oconcentration concentrationLow solute High soluteconcentration concentration • There are 3 types of “environments” a cell can be in based on solute concentration. They are called hypertonic, hypotonic, and isotonic.
    • 21. • A simple rule to remember is: Salt Steals!!!• Salt is a solute. When it is concentrated inside or outside of the cell, it will draw the water in its direction. This is also why you get thirsty after eating something salty. However, this works for any solute, not just salt…it could be sugar, for example.
    • 22. Direction of Osmosis• In a Hypertonic solution, the concentration of solute (ex. salt) outside the cell is higher than the concentration inside the cell. − The word "HYPER" means MORE. Just think, you are HYPER when you have MORE energy. In this case, there are more solute (ex. salt) molecules outside the cell, and because “salt steals” it will “steal” or draw the water in its direction. In other words, water diffuses out of the cell.
    • 23. Direction of Osmosis• In a Hypotonic solution, the concentration of solute (ex. salt) outside the cell is lower than the concentration inside the cell. − The word "HYPO" means LESS. In this case, there are less solute (ex. salt) molecules outside the cell, and since “salt steals”, water diffuses into the
    • 24. Direction of Osmosis• In an Isotonic solution, the concentration of solutes is equal outside and inside of the cell. − “ISO" means the SAME. If the concentration of solute (ex. salt) is equal on both sides, water diffuses into and out of the cell at equal rates but it wont have any effect on the overall amount of
    • 25. = solute(like salt) = water membranehigh concentration of solute lower concentration of solute HYPERTONIC HYPOTONIC ENVIRONMENT ENVIRONMENT
    • 26. = solute(like salt) = waterhigh concentration lower concentration of solute of solute
    • 27. = solute(like salt) = waterhigh concentration lower concentration of solute of solute
    • 28. = solute(like salt) = waterhigh concentration lower concentration of solute of solute
    • 29. The net flow of water is towards the higher solute concentration. high concentration lower concentration of solute of solute• How Osmosis Works
    • 30. How Cells Deal With Osmosis• How Freshwater Cells Deal with Osmosis − When organisms live in freshwater environments (like a pond), they are living in a hypotonic environment. − Therefore, water is constantly diffusing into them. − Some of them, like a Paramecium, have a special structure called a contractile vacuole which collects water then pumps in out of the cell.
    • 31. How Cells Deal With Osmosis• How Plant Cells Deal with Osmosis in a Hypotonic Environment – Plants have roots surrounded by water and usually live in a HYPOtonic environment. 1) Water diffuses INTO the cells through osmosis. 2) Water may be stored in the vacuole. 3) The water molecules exert pressure against the cell wall. – This pressure is known as turgor pressure. 1) The cell wall is strong enough to prevent the cell from bursting open.
    • 32. How Cells Deal With Osmosis• How Plant Cells Deal with Osmosis in a Hypertonic Environment – If a Plant is in a HYPERtonic environment: 1) Water diffuses OUT OF the cells through osmosis. 2) Cells shrink away from the cell walls and turgor pressure is lost. a) This condition is called plasmolysis, and is the reason that plants wilt. (lysis means to die in Latin)
    • 33. Turgor Pressure and Plasmolysis Turgor Pressure Plasmolysis• Movement of Water by Osmosis in Plant Cell
    • 34. How Cells Deal With Osmosis• How Animal Cells Deal with Osmosis in a HYPOtonic environment – If animal cells like red blood cells are in a hypotonic environment: 1) Water diffuses INTO the cells through osmosis. 2) No cell wall is present to prevent the cell from bursting. 3) When a cell bursts it is called cytolysis. (again lysis means “to die”)
    • 35. How Cells Deal With Osmosis• How Animal Cells Deal with Osmosis in a HYPERtonic environment – If animal cells like red blood cells are in a hypertonic environment: 1) Water diffuses OUT OF the cells through osmosis. 2) The cells shrink and shrivel. This process is known as crenation.• Animal Cell in Different Solutions
    • 36. Example of Cell Crenation• One way that people try to remove slugs from their garden is by pouring salt on them.• When you pour salt on a slug, it appears to “melt”.• What is actually happening is that the slug is in a hypertonic environment.• Through osmosis, water and fluids will move out of the slugs body causing it to shrivel, an example of cell crenation.
    • 37. Three Types of Solutions Cytolysis Crenation Turgor PressurePlasmolysis
    • 38. Facilitated Diffusion• Another type of Passive Transport is called Facilitated Diffusion – Facilitated diffusion occurs for molecules that cannot diffuse through cell membranes, even when there is a concentration gradient. • Example: Molecules that are just too BIG to pass directly through the membrane. – Again, no energy is required. – Diffusion through the membrane is facilitated, or helped, by proteins called carrier proteins. – Carrier Protein: A special type of integral protein inside the membrane that acts as a “tube” to let larger molecules through the membrane. – Only occurs when molecules are going DOWN their concentration gradient—must be going from high concentration to low concentration. – Carrier proteins involved in facilitated diffusion are each specific for one type of molecule. Carrier Protein Cell Membrane
    • 39. Facilitated Diffusion• Example of Facilitated Diffusion: Molecules of glucose, which are the cell’s source of energy, are too large to pass through the membrane and must move into cells by facilitated diffusion.• How Facilitated Diffusion Works
    • 40. Diffusion Through Ion Channels• Ion channels – transport ions such as sodium (Na+), potassium (K+), calcium (Ca2+), and chloride (Cl-)• When ion channels transport ions from higher to lower concentrations they are a form of passive transport.• Each type of ion channel is usually specific for one type of ion.• Some ion channels are always open.• Some have “gates” that open and close in response to: − Stretching of the cell membrane − Electrical signals − Chemicals in the cell or external environment
    • 41. Active Transport• Movement of materials across the cell membrane from an area of lower concentration to an area of higher concentration (“up” or “against” their concentration gradient).• Requires energy from the cell. − It is like riding a bike uphill.
    • 42. Types of Active Transport • Cell Membrane Pumps • Endocytosis • Exocytosis
    • 43. Cell Membrane Pumps• Some types of active transport are performed by carrier proteins called cell membrane pumps.• These carrier proteins function in the same way as the carrier proteins used in facilitated diffusion. – The molecule to be transported binds to the carrier protein on one side of the cell membrane. – The carrier protein changes shape, shielding the molecule from the hydrophobic interior of the phospholipid bilayer. – The carrier protein then transports the molecule through the membrane and releases it on the other side. – Unlike the carrier proteins used in facilitated diffusion, cell membrane pumps require energy.• Example: Sodium-Potassium Pump
    • 44. Sodium-Potassium Pump• The sodium-potassium pump moves 3 Na+ ions out of the cell for every 2 K+ ions it moves into the cell. Both ions move up or against their concentration gradients. − To function normally, some animal cells must have a higher concentration of Na+ ions outside the cell and a higher concentration of K+ ions inside the cell. − The sodium-potassium pump maintains these concentration differences.• ATP supplies the energy that drives the pump.
    • 45. Sodium-Potassium Pump
    • 46. Steps of the Sodium-Potassium Pump1. Three Na+ ions from the inside of the cell bind to the carrier protein.
    • 47. Steps of the Sodium-Potassium Pump2. A phosphate group is removed from ATP and bound to the carrier protein.
    • 48. Steps of the Sodium-Potassium Pump3. The carrier protein changes shape, allowing three Na+ ions to be released to the outside of the cell.
    • 49. Steps of the Sodium-Potassium Pump4. Two K+ ions from the outside of the cell bind to the carrier protein.
    • 50. Steps of the Sodium-Potassium Pump5. The phosphate group is released and the carrier protein goes back to its original shape.
    • 51. Steps of the Sodium-Potassium Pump 6. The two K+ ions are released to the inside of the cell and the cycle is ready to repeat.• How the Sodium-Potassium Pump Works
    • 52. Importance of the Sodium-Potassium Pump• The ion exchange creates an electrical gradient across the cell membrane. – Outside becomes positively charged. – Inside becomes negatively charged.• This difference in charge is important for the conduction of electrical impulses along nerve cells.• Helps muscle cells contract. – People drink sports drinks when they exercise to replace some of the sodium and potassium ions that are important for this pump. Without these ions you would get muscle cramps.
    • 53. Movement in Vesicles• Some substances, such as macromolecules, solid clumps of food, and whole cells are too large to pass through the cell membrane by the transport processes studied so far.• Cells employ two other transport mechanisms– endocytosis and exocytosis–to move such substances into or out of cells. – Both of these mechanisms require cells to expend energy. Therefore, they are types of active transport.
    • 54. Endocytosis• “Endo” means inside and “cytosis” refers to the cytoplasm. So, endocytosis brings bulky material into the cytoplasm.• In endocytosis, cells ingest external materials by the cell membrane folding around them and forming a pouch.• The pouch then pinches off and becomes a membrane-bound organelle called a vesicle that holds the materials.• Some of the vesicles fuse with lysosomes, and their contents are digested by lysosomal enzymes.• Other vesicles fuse with other membrane-bound organelles.
    • 55. Endocytosis
    • 56. Endocytosis• Two Types: (1) Phagocytosis – “cell eating”; solid particles are engulfed by the cell Example: The white blood cells known as phagocytes engulf invading microorganisms by this process. (1) Pinocytosis – “cell drinking”; liquid particles are engulfed by the cell• Endocytosis
    • 57. Exocytosis• The opposite of endocytosis is called exocytosis.• “Exo” means “out”.• Process by which bulky substances are released from the cell through a vesicle that transports the substances to the cell surface and then fuses with the membrane to let the substances out of the cell.
    • 58. Exocytosis• Example: Hormones or wastes released from cell
    • 59. Exocytosis• Exocytosis
    • 60. Summary Weeee!!!• Passive Transport-cell does NOT use energy  Diffusion  Osmosis  Facilitated Diffusion  Diffusion Through Ion Channels high low• Active Transport-cell does use energy  Cell Membrane Pumps This is gonna  Endocytosis be hard 1. Phagocytosis – “cell eating” work!!! 2. Pinocytosis – “cell drinking” high  Exocytosis low

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