AS Biology. Foundation. Cell membranes and Transport1 CELL MEMBRANES and TRANSPORT

AS Biology. Foundation. Cell membranes and Transport2 The Cell

AS Biology. Foundation. Cell membranes and Transport3 Cell membrane  All living things are surrounded by a membrane.  A cell membrane is also known as plasma membrane.  Controls exchange of materials such as nutrients and waste between cells and their environment.  Has other important functions for example to enable cells to receive hormones.  To understand the function of anything in biology, you must study the structure first!

AS Biology. Foundation. Cell membranes and Transport4 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 Transport5  HYDROPHILIC heads (water liking) -Attracted to the water  called POLAR  HYDROPHOBIC tails (water fearing) -Not attracted to the water  called NON-POLAR Cell membranes are made of PHOSPHOLIPIDs A Phospholipid

AS Biology. Foundation. Cell membranes and Transport6 A phospholipid HYDROPHILIC HEAD At the other 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 HYDROPHOBIC TAILS The two long chains coming off of the bottom of this molecule are made up of carbon and hydrogen. Because both of these elements share their electrons evenly these chains have no charge. They are NON POLAR. Molecules with no charge 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 Transport7 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 Transport8 Fluid mosaic model Cell membranes also contain proteins within the phospholipid bilayer. This ‘model’ for the structure of the membrane is called the: FLUID MOSAIC MODEL FLUID- because individual phospholipids and proteins can move around freely 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.

AS Biology. Foundation. Cell membranes and Transport9 Cell Membranes from Opposing Neurons (TEM x436,740). } Phospholipid Bilayer 7nm wide

AS Biology. Foundation. Cell membranes and Transport10 Movement of selected molecules across the cell membrane

AS Biology. Foundation. Cell membranes and Transport11 Methods of Transport Across Membranes 1. Diffusion 2. Osmosis 3. Facilitated Diffusion 4. Active Transport

AS Biology. Foundation. Cell membranes and Transport12 Methods of Transport Across Membranes 1. Diffusion -passive transport - no energy expended energy expended 2. Osmosis - Passive transport of water across membrane 3. Facilitated Diffusion - Use of proteins to carry polar molecules or ions across carry polar molecules or ions across 4. Active Transport- requires energy to transport molecules against a transport molecules against a concentration gradient – energy is concentration gradient – energy is in the form of ATP in the form of ATP

AS Biology. Foundation. Cell membranes and Transport13 Diffusion  Movement of molecules from an area of high concentration to an area of low concentration.  Movement from one side of a membrane to another, un- facilitated

AS Biology. Foundation. Cell membranes and Transport14 Diffusion

AS Biology. Foundation. Cell membranes and Transport15 Solutions  Solutions are made of solute and a solvent  Solvent - the liquid into which the solute is poured and dissolved. We will use water as our solvent today.  Solute - substance that is dissolved or put into the solvent. Salt and sucrose are solutes.

AS Biology. Foundation. Cell membranes and Transport16 Osmosis

AS Biology. Foundation. Cell membranes and Transport17 Tonicity is a relative term  Hypotonic Solution - One solution has a lower concentration of solute than another.  Hypertonic Solution - one solution has a higher concentration of solute than another.  Isotonic Solution - both solutions have same concentrations of solute.

AS Biology. Foundation. Cell membranes and Transport18 Plant and Animal Cells put into various solutions

AS Biology. Foundation. Cell membranes and Transport19 Types of Transport

AS Biology. Foundation. Cell membranes and Transport20 Diffusion Lab  We are using dialysis tubing as the cell membrane - It is selectively permeable  The solute is either the eosin starch solution or the sugar solution  What is the solvent?

AS Biology. Foundation. Cell membranes and Transport21 Membrane Permeability  Solute is eosin-starch-chloride solution  Solvent is Water  Indicator for presence of starch is IKI  Starch is made of amylose and amylopectin – amylopectin is insoluble  Iodine is not very soluble in water, but with KI it forms a I 3 - (triiodine ion) which is soluble.  I 3 - combines with the amylose and the starch molecule turns blue-black.

AS Biology. Foundation. Cell membranes and Transport22 Test for Starch Elmhurst College Website

AS Biology. Foundation. Cell membranes and Transport23 Test for Chloride ions  Indicator for presence of chloride ions is silver nitrate, AgNO 3 A white precipitate, AgCl, forms if chloride is present. A white precipitate, AgCl, forms if chloride is present.

AS Biology. Foundation. Cell membranes and Transport24 Test for Sulfate ions  Indicator for the presence of sulfate ions is Barium chloride, BaCl Barium sulfate, BaSO 4 - forms a white precipitate Barium sulfate, BaSO 4 - forms a white precipitate BaCl + NaSO > BaSO 4 + NaCl BaCl + NaSO > BaSO 4 + NaCl

AS Biology. Foundation. Cell membranes and Transport25 Living Cells  Fern gametophytes are used to see result of putting live cells in solutions of varying tonicity

AS Biology. Foundation. Cell membranes and Transport26 Osmosis  We will make an osmometer to see osmosis  Sugar solution in a dialysis tube is used to simulate a cell membrane.  Various concentrations of solute may be used around the room.

AS Biology. Foundation. Cell membranes and Transport27  Moving amoeba