BUBBLES MUST wear goggles at ALL times NO

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

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

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 3

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

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

L 3 Biology Chapter 4 CELL MEMBRANES and TRANSPORT Visit www. worldofteaching. com AS Biology. Foundation. Cell membranes and Transport For 100’s of free powerpoints 6

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

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 Transport 8

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

Cell Membranes from Opposing Neurons (TEM x 436, 740). Nerve cell Cell membrane { Gap between cells } cell membrane 7 nm wide Nerve cell AS Biology. Foundation. Cell membranes and Transport 10

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

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

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

Why is it a A phospholipid 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 AS Biology. Foundation. Cell membranes and Transport 3 D model of a Phospholipid 14

Why are they A phospholipid 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. AS Biology. Foundation. Cell membranes and Transport 3 D model of a Phospholipid 15

A Phospholipid Bilayer 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. AS Biology. Foundation. Cell membranes and Transport 16

AS Biology. Foundation. Cell membranes and Transport 17

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

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

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

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 21

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 22

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

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

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

What is the function of cholesterol? Ø 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 26

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

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

Ø The Summary fatty acid tails of phospholipids can be SATURATED (straight) or UNSATURATED (bent) Ø Phospholipids form the bilayer, act as barrier to most water soluble substances Ø 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 30

Ø Proteins Summary can float or be fixed and also have hydrophobic and hydrophilic portions. Ø 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 31

Ø Some Summary proteins and phospholipids have carbohydrates attached to them to form GLYCOPROTEINS AND GLYCOLIPIDS. Ø 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 32

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

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 34

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 1. Phospholipids 2. Cholesterol 3. Proteins 4. Glycolipids and Glycoproteins AS Biology. Foundation. Cell membranes and Transport 35

L 3 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 36

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 37

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