AS Biology. Foundation. Cell membranes and Transport1 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 Transport2 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 Transport3 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 Transport4 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 Transport5 COPY these key words and define:  Phospholipids  Polar  Hydrophilic  Hydrophobic  Cholesterol  Transport proteins  Selectively permeable  Phospholipid bilayer  Fluid mosaic model  Glycoproteins  Glycolipids

AS Biology. Foundation. Cell membranes and Transport6 L3 Biology Chapter 4 CELL MEMBRANES and TRANSPORT Visit For 100’s of free powerpoints

AS Biology. Foundation. Cell membranes and Transport7 The Cell

AS Biology. Foundation. Cell membranes and Transport8 Learning Objectives 1. Describe the fluid mosaic model of membrane structure and explain the underlying reasons for this structure. 2. Outline the roles of phospholipids, cholesterol, glycolipids, proteins and glycoproteins in membranes. 3. Outline the roles of the plasma membrane, and the roles of membranes within cells.

AS Biology. Foundation. Cell membranes and Transport9 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 Transport10 Cell Membranes from Opposing Neurons (TEM x436,740). } cell membrane 7nm wide Cell membrane { Nerve cell Gap between cells

AS Biology. Foundation. Cell membranes and Transport11  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 WHAT are POLAR Molecules?

AS Biology. Foundation. Cell membranes and Transport12  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 Transport13 Plasma Membrane Structure  Building blocks are phospholipids… Lipid with a polar phosphate group attached to one end. Lipid with a polar phosphate group attached to one end.

AS Biology. Foundation. Cell membranes and Transport14 A phospholipid 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 3D model of a Phospholipid

AS Biology. Foundation. Cell membranes and Transport15 A phospholipid 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. 3D model of a Phospholipid

AS Biology. Foundation. Cell membranes and Transport16 A Phospholipid Bilayer Phospholipids can form: BILAYERS -2 layers of phospholipids with hydrophobic tails protected inside by the hydrophilic heads. hydrophobic tails protected inside by the hydrophilic heads. The PHOSPHOLIPID BILAYER is the basic structure of membranes.

AS Biology. Foundation. Cell membranes and Transport17

AS Biology. Foundation. Cell membranes and Transport18 Properties of Cell Membranes 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 Transport19 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 Transport20 Diagram representing the cell membrane Remember the membrane is 7nm wide

AS Biology. Foundation. Cell membranes and Transport21 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 Transport22 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 Transport23 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 Transport24 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.

What is Cholesterol- A Lipid! AS Biology. Foundation. Cell membranes and Transport25

AS Biology. Foundation. Cell membranes and Transport26 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.

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AS Biology. Foundation. Cell membranes and Transport28 Wrap-up! How is the cell’s membrane structured (chemically) to ensure efficiency and survival?

AS Biology. Foundation. Cell membranes and Transport29 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 Transport30 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 Transport31 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 Transport32 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 Transport33 Visualizing structure and function  _innerlife.html multimedia.mcb.harvard.edu/anim _innerlife.htmlmultimedia.mcb.harvard.edu/anim _innerlife.html

AS Biology. Foundation. Cell membranes and Transport34 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 Transport35 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. ComponentStructure Functions 1. Phospholipids 2. Cholesterol 3. Proteins 4. Glycolipids and Glycoproteins

AS Biology. Foundation. Cell membranes and Transport36 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 Transport37 Movement of selected molecules across the cell membrane

AS Biology. Foundation. Cell membranes and Transport38  Moving amoeba  Contractile vacuole