BUBBLES!!

1. BUBBLES!! • MUST wear goggles at ALL times! • NO taking straw out of the dish! • NO drinking/ inhaling bubble fluid • THIS IS an EXPERIMENT!!! • You can have fun, but ALL usual lab safety RULES APPLY! AS Biology. Foundation. Cell membranes and Transport

2. Questions to think about: • Can anything pass through the bubble without breaking it? • Can one bubble divide to become several bubbles? • Can several bubbles merge to form one- how? • Can a drop of water pass through a bubble without popping it? • Does it look like the surface of the bubble moves? How can you tell? AS Biology. Foundation. Cell membranes and Transport

3. soapy “membranes” 1. How does a bubble model the fluid nature of a membrane? 2. Can anything pass through the membrane without rupturing it? If so what; if no, what did you try? 3. Can one bubble divide to become several bubbles? 4. Can several bubbles merge to become one bubble? 5. Can a drop of water pass through a bubble without popping the bubble? 6. A bubble is a lipid monolayer – draw a diagram of a segment of a bubble using this symbol for a lipid molecule: AS Biology. Foundation. Cell membranes and Transport

4. Bubble Summary! • A bubble is a lipid monolayer!! • What is the structure of the membranes of our cells? • How does a bubble model the fluid nature of a cell membrane? AS Biology. Foundation. Cell membranes and Transport

5. Phospholipids Polar Nonpolar Hydrophilic Hydrophobic Cholesterol Transport proteins Selectively permeable Phospholipid bilayer Fluid mosaic model Glycoproteins Glycolipids Key Terms: AS Biology. Foundation. Cell membranes and Transport

6. L3 BiologyChapter 4CELL MEMBRANESandTRANSPORT Visit www.worldofteaching.com For 100’s of free powerpoints AS Biology. Foundation. Cell membranes and Transport

7. The Cell AS Biology. Foundation. Cell membranes and Transport

8. Learning Objectives • Describe the fluid mosaic model of membrane structure and explain the underlying reasons for this structure. • Outline the roles of phospholipids, cholesterol, glycolipids, proteins and glycoproteins in membranes. • Outline the roles of the plasma membrane, and the roles of membranes within cells. AS Biology. Foundation. Cell membranes and Transport

9. Cell membrane (aka Plasma Membrane) • All living things are surrounded by a membrane. • It controls exchange of materials (like nutrients, waste) between cells and their environment. • It has other important functions ie.to enable cells to communicate to other cells or respond to hormones. • To understand the function of anything in biology, you must first study the structure! AS Biology. Foundation. Cell membranes and Transport

10. Cell Membranes from Opposing Neurons (TEM x436,740). Nerve cell Gap between cells Cell membrane { } cell membrane 7nm wide Nerve cell AS Biology. Foundation. Cell membranes and Transport

11. WHAT are POLAR Molecules? • HYDROPHILIC (water liking) • Due to unequal distribution of electrons (negative charge). • One end of molecule is partially positive while other end is partially negative. The molecule has ‘poles’ • HYDROPHOBIC (water fearing) are NONPolar AS Biology. Foundation. Cell membranes and Transport

12. HYDROPHILIC heads (water loving)-Attracted to the water called POLAR head HYDROPHOBIC tails (water fearing)-Not attracted to the water called NON-POLAR Tail PHOSPHOLIPIDs are POLAR AND Nonpolar Molecules A Phospholipid AS Biology. Foundation. Cell membranes and Transport

13. Plasma Membrane Structure • Building blocks are phospholipids… • Lipid with a polar phosphate group attached to one end. AS Biology. Foundation. Cell membranes and Transport

14. Why is it a HYDROPHILIC HEAD? One end of the phospholipid is a phosphate group and several double bonded oxygens. The atoms at this end of the molecule are not shared equally. This end of the molecule has a charge and is attracted to water. It is POLAR A phospholipid 3D model of a Phospholipid AS Biology. Foundation. Cell membranes and Transport

15. Why are they HYDROPHOBIC TAILS Two long chains at bottom are made up of carbon and hydrogen. Both these elements share their electrons evenly, which means these chains have no charge (are NON POLAR). This means they are not attracted to water; as a result water molecules tend to push them out of the way as they are attracted to each other. This causes molecules with no charge not to dissolve in water. A phospholipid 3D model of a Phospholipid AS Biology. Foundation. Cell membranes and Transport

16. Phospholipids can form: BILAYERS -2 layers of phospholipids with hydrophobic tails protected inside by the hydrophilic heads. The PHOSPHOLIPID BILAYER is the basic structure of membranes. A Phospholipid Bilayer AS Biology. Foundation. Cell membranes and Transport

17. AS Biology. Foundation. Cell membranes and Transport

18. Properties of Cell Membranes • Basic structure is Phospholipid Bilayer. • Phospholipids have HYDROPHOBIC (non-polar) tails and HYDROPHILIC (polar) heads. • The fatty acid tails of phospholipids can be SATURATED (straight) or UNSATURATED (bent) AS Biology. Foundation. Cell membranes and Transport

19. Properties of Cell Membranes • Phospholipids act as a barrier to most water soluble substances • BUT, Phospholipids are only PART of the story………… AS Biology. Foundation. Cell membranes and Transport

20. Diagram representing the cell membraneRemember the membrane is 7nm wide AS Biology. Foundation. Cell membranes and Transport

21. Fluid mosaic model Cell membranes also contain cholesterol and proteins within the phospholipid bilayer. This ‘model’ for the structure of the membrane is called the: FLUID MOSAIC MODEL AS Biology. Foundation. Cell membranes and Transport

22. Why call it a Fluid Mosaic Model? FLUID- because phospholipids and proteins move around freely within the layer, like it’s a liquid. MOSAIC- because of the pattern produced by scattered protein molecules in the membrane when viewed from above. AS Biology. Foundation. Cell membranes and Transport

23. Where are the proteins? Proteins can float or be fixed and also have hydrophobic and hydrophilic portions. • Some proteins and phospholipids have carbohydrates attached to them to form GLYCOPROTEINS AND GLYCOLIPIDS. AS Biology. Foundation. Cell membranes and Transport

24. Functions of Proteins • 1. Proteins act as channels for substances to move in or out of cell. • 2. Some act as membrane enzymes in chemical reactions. • 3. Proteins help to stabilize the membrane • 4. glycoproteins act as markers for cell communication or receptors that hormones & other proteins can bind. AS Biology. Foundation. Cell membranes and Transport

25. What is Cholesterol- A Lipid! AS Biology. Foundation. Cell membranes and Transport

26. What is the function of cholesterol? • Cholesterol regulates the fluidity of the membrane, gives mechanical stability and help to prevent ions from passing through the membrane. AS Biology. Foundation. Cell membranes and Transport

27. AS Biology. Foundation. Cell membranes and Transport

28. Wrap-up! How is the cell’s membrane structured (chemically) to ensure efficiency and survival? AS Biology. Foundation. Cell membranes and Transport

29. Summary • Cell membranes have a basic structure composed of a PHOSPHOLIPID BILAYER. • Phospholipds have HYDROPHOBIC (non-polar) tails and HYDROPHILIC (polar) heads. • The best model of the cell membrane is called the FLUID MOSAIC MODEL • The average thickness of the membrane is 7nm. AS Biology. Foundation. Cell membranes and Transport

30. Summary • The fatty acid tails of phospholipids can be SATURATED (straight) or UNSATURATED (bent) • Phospholipids form the bilayer, act as barrier to most water soluble substances • Cholesterol regulates the fluidity of the membrane, gives mechanical stability and help to prevent ions from passing through the membrane. AS Biology. Foundation. Cell membranes and Transport

31. Summary • Proteins can float or be fixed and also have hydrophobic and hydrophilic portions. • Proteins act as transport proteins to act as channels for substances to move into or out of the cell. Some act as membrane enzymes and some have important roles in membranes of organelles. AS Biology. Foundation. Cell membranes and Transport

32. Summary • Some proteins and phospholipids have carbohydrates attached to them to form GLYCOPROTEINS AND GLYCOLIPIDS. • Glycolipids and Glycoproteins help to stabilise membrane structure, some act as receptor molecules (eg for hormones and neurotransmitters) or as antigens for other cells to recognise them. AS Biology. Foundation. Cell membranes and Transport

33. Visualizing structure and function • membrane animation AS Biology. Foundation. Cell membranes and Transport

34. Wrap-up! How is the cell’s membrane structured (chemically) to ensure efficiency and survival? -Is it ever the same?? AS Biology. Foundation. Cell membranes and Transport

35. Functions of components of cell membranes Use the following headings to produce a table summarizing the functions of the different types of molecules found in the cell membrane. Use your notes to find the information. Component Functions • Phospholipids • Cholesterol • Proteins • Glycolipids and Glycoproteins AS Biology. Foundation. Cell membranes and Transport

36. L3 Quick Check: 1. Name 2 functions for proteins in the membrane. 2. a. What do we call a protein with a carbohydrate (sugar) attached? b. Name 1 function for these molecules in the membrane. 3. Name 2 functions of cholesterol in the cell membrane? AS Biology. Foundation. Cell membranes and Transport

37. 4. a. What is the main component of the cell membrane? b. Name the 2 parts of this molecule? c. Name one function for this mol. 5. a. What does the word “hydrophobic” mean? b. What does the word “hydrophilic” mean? AS Biology. Foundation. Cell membranes and Transport

38. Preview of coming attractions! • Membrane structure allows for the movement of substances into and out of the cell • Living organisms demonstrate many adaptations to their membranes allowing them to survive in their environments! AS Biology. Foundation. Cell membranes and Transport

39. Movement of selected molecules across the cell membrane AS Biology. Foundation. Cell membranes and Transport

40. Moving amoeba • Contractile vacuole AS Biology. Foundation. Cell membranes and Transport