Chapter 4 –Section 4.2 (pgs. 56 – 57) Chapter 5 (5.6, 5.7 and 5.8 - pgs. 88-93)

1. Chapter 4 –Section 4.2 (pgs. 56 – 57) Chapter 5 (5.6, 5.7 and 5.8 - pgs. 88-93)

2. Chapter 4 & 5 Unit Objectives • Students will be able to: • Describe how parts of the plasma membrane are used for various types of cell transport, regulation and exchange of substances and communication with the environment. • Explain how materials move across the plasma membrane based on concentration gradient. • Explain the movement of water in isotonic, hypotonic and hypertonic solutions and how both animal and plant cells are affected in each. • Explain turgor pressure • Compare and contrast endocytosis and exocytosis and explain their function. • Compare and contrast passive and active transport and be able to give examples of each.

3. Chapter 4 and 5 MEMBRANE STRUCTURE AND FUNCTION • - Each cell is surrounded by a plasma membrane • - The plasma membrane separates the living cell from its nonliving surroundings • - It allows only specific substances in and out of the cell (selectively permeable) • - Passes chemical messages from external environment to the internal cell

4. Characteristic of Membranes • Major mechanisms of molecular transport in cells • Regulates what enters and leaves the cell • Permeable – materials pass through freely • Selectively Permeable Membrane – Allow only certain substances to pass through – depends on the cells needs.

5. Factors that affect permeability • Size of molecules – example – large molecules do not pass as freely as smaller ones. • Cells needs • Environment • Solubility • Composition of the membrane

6. Membrane Structure Review Polar group Glycerol Fatty Acid Fatty Acid Phosphate containing head (hydrophilic) and two fatty acids tails (hydrophobic) Non-polar

7. Membrane Structure - The plasma membranes lipids form a two-layered membrane called the lipid bilayer - The lipid bilayer is an arrangement of hydrophilic heads and hydrophobic tails Outside cell Hydrophilic head Hydrophobic tail Cytoplasm (inside cell) (a) lipid bilayer of membrane

8. Most membranes have specific proteins • embedded in the lipid bilayer This is called the fluid mosaic model of the plasma membrane Hydrophilic region of protein lipid bilayer Hydrophobic region of protein (b) Fluid mosaic model of membrane

9. Fluid Mosaic Modelof Membrane Structure

10. Membrane Proteins and Their Function • Water can cross the membrane freely but ions and most polar molecules cannot. • Integral Proteins – detect environmental signals and transmit them to the inside of the cell. • Peripheral Proteins – lie on one side of the membrane. They often have carbohydrates attached that act as labels on cell surfaces. Act as recognition. • Functions • Regulation and exchange of substances • Communication with the environment

11. Physical Laws of Motion (molecular motion) Solids – vibrate in space Liquids – Flow Gases – move very freely and quickly Brownian Movement – Constant random molecular motion – Molecules move from areas of high concentration to low concentration

12. - Net movement of molecules from regions of high concentration to regions of low concentration. - Down a concentration gradient - Doesn’t require energy, like riding a bike down hill - Movement continues until substances are evenly distributed (equilibrium is reached) Equilibrium – Concentration gradient (difference in the concentration of molecules across a distance) no longer exists, molecules still move but there is no net movement. Concentration of molecules will be the same. Simple Diffusion – movement across a membrane

13. Simple Diffusion (extracellular fluid) Some moleculesdiffuse freelyacross (cytoplasm)

14. Diffusion of Dye in Water RandomDispersal Dispersing Time 0 Time 1 Time 2 SteepConcentrationGradient ReducedConcentrationGradient NoConcentrationGradient

15. Factors that affect the rate of diffusion • Concentration – increase in concentration increases the rate • Temperature – increase in temperature increases the rate (hot water and dye) • Pressure – increase in pressure increases the rate

16. Diffusion of water across a membrane Special case of diffusion Net movement of water molecules from an area of high water concentration to an area of low water concentration The cell has no control over osmosis, it is due to the concentration gradient inside and outside of the cell. Osmosis

17. Concentration Gradient Concentration Gradient – Is determined by the concentration of solute (ex. Salt) on each side of the membrane (differences in amount) of molecules or substances. Remember! Osmosis is looking at which way water moves. (Example on Board)

18. Types of solutions or Environments of Cells What happens to a red blood cell in different solutions? Isotonic Solution – solution that has the same concentration of dissolved particles as the cytoplasm. Thus, water inside and outside of the cell are equal and there will be equal movement. (example on board)

19. Types of solutions or Environments of Cells Hypotonic Solution – solution has lower concentration of dissolved particles than the cytoplasm of a cell. Thus, more water is outside the cell than inside the cell so water will move into the cell from high to low. (example on board)

20. Types of solutions or Environments of Cells Hypertonic Solution – solution that has a higher concentration of dissolved particles (less water) than the cytoplasm. Thus, less water outside of the cell so water moves out of the cell from high concentration to low, into solution . (example on board)

21. The Effects of Osmosis Hypotonic Solution Hypertonic Solution Isotonic Solution

22. Osmotic Factors – what happened to plant cells in isotonic, hypotonic a hypertonic conditions? • Osmotic Pressure: pressure that builds up in a plant cell due to osmosis. • Isotonic Solution: no change in cell • Solution of equal water concentration and solute concentration • The plants will neither gain or lose water • Plant is normal and healthy • Hypotonic Solution: plant gains water and pushes the membrane up against the cell wall. • The cell wall is strong enough to resist the pressure exerted by the water inside the expanding cell – TURGOR PRESSURE • High concentration of water and a lower concentration of solute (ex. sugar or salt) • Hypertonic solution: cell will shrink away from the cell wall plasmolysis • This is why plants wilt • Low concentration of water and a high concentration of solute (ex. sugar or salt)

23. Plants Reaction to Different Solutions

24. Plants Reaction to Different Solutions

25. Osmotic Factors – what happened to animal cells in isotonic, hypotonic a hypertonic conditions? • Isotonic Solution: no change in cell • Solution of equal water concentration and solute concentration • Hypotonic Solution: water enters the cell, cell will swell / burst/cell lysis. The membrane ruptures. • High concentration of water and a lower concentration of solute (ex. sugar or salt) • Hypertonic solution: water leaves the cell,it will shrink / crenate • Low concentration of water and a high concentration of solute (ex. sugar or salt)

26. Animal Cell (red blood cell) Reaction to Different Solutions

27. Animal Cell (red blood cell) Reaction to Different Solutions

28. Cells Reaction to Different Solutions

29. Plasma membrane provides two types of movement I. Passive Transport Substances move into and out of cells along concentration gradients Move from an area of high concentration to low concentration Does not require energy Types of Passive Transport: - Simple Diffusion - Osmosis - Facilitated Diffusion – diffusion using a carrier protein/channel protein. Molecule is to large to go through the membrane. Types of Transport Processes

30. Facilitated Diffusion • Facilitated Diffusion: • Down a concentration gradient, from high concentration to low concentration • Entrance is via channel or carrier proteins • Does not require energy

31. Facilitated Diffusion: Carriers DiffusionChannelProtein (OutsideCell) Molecule inTransit DiffusionGradient Carrier proteinhas binding sitefor molecule Carrier protein changesshape, transportingmolecule across membrane Molecule entersbinding site Carrier protein resumesoriginal shape (Inside Cell)

32. II. Active Transport Substances move against a concentration gradient Move from low concentration to high concentration Requires energy (ATP) Types of Transport Processes

33. - Requires that the cell expend energy to move molecules across a membrane - Movement of molecules against a concentration gradient - From low concentration to high concentration - Maintains internal (inside cell) concentrations of molecules that differ from external (out side cell) environment concentrations Active Transport

34. Active Transport: the Pumping of Molecules Across Membranes • Transport proteins have specific binding sites that only accepts specific molecules. Using energy, the protein pumps the solute molecule against a concentration gradient and into the cell Lower solute concentration Solute Higher solute concentration Figure 5.15

35. Types of Active Transport Exocytosis and Endocytosis are methods of active transport that move large molecules across a membrane

36. Endocytosis • Endocytosis: takes material into the cell by forming pockets in the membrane • Types of endocytosis • Phagocytosis – engulfing large particles – cell eating • Pinocytosis – engulfing smaller particles – cell drinking Figure 5.16b (b) Endocytosis

37. Endocytosis • In phagocytosis (“cellular eating”) a cell engulfs a large particle and packages it within a food vacuole In pinocytosis (“cellular drinking”) a cell “gulps” droplets of fluid or small particles by forming tiny vesicles Food being ingested Figure 5.17

38. Exocytosis • Exocytosis • Secretes substances outside of the cell. Removing particles. Outside cell Plasma membrane Cytoplasm (a) Exocytosis

39. Exocytosis SecretedMaterial (extracellular fluid) plasma membrane 3 2 Vesicle 1 (cytoplasm)

40. Another example of active transport in animal cells is the Sodium Potassium Pump and it involves a carrier protein. The protein transports sodium (Na+) ions and potassium (k+) ions against a concentration gradient. To function normally, some animal cells must have a higher concentration of Na+ ions outside of the cell and higher concentration of K+ ions inside the cell. Sodium potassium pump maintains these concentration differences. THIS TAKES ATP Active Transport – Sodium Potassium Pump

41. Active Transport – Sodium Potassium Pump

42. The End