Membrane structure Describe the structure of a phospholipid bilayer Analyse models of membrane structures Describe the falsification of the Davson-Danielli model Describe how membrane proteins are diverse Draw the fluid mosaic model of membrane structure Explain the role of cholesterol in membranes

Phosphate group and 2 hydrocarbon chains Phospholipids

Phospholipids are AMPHIPATHIC Part of the molecule is hydrophilic Part of the molecule is hydrophobic

Phosphate group and 2 hydrocarbon chains Draw and label your own! Drawing phospholipids

When mixed with water, phosphate heads are attracted to water and hydrocarbon tails attracted to each other but not water Phospholipid bilayer Create a double layer Basis of all cell membranes

Membrane structure Describe the structure of a phospholipid bilayer Analyse models of membrane structures Describe the falsification of the Davson-Danielli model Describe how membrane proteins are diverse Draw the fluid mosaic model of membrane structure Explain the role of cholesterol in membranes

Models of membrane structures Gortor and Grendel 1920s Davson and Danielli 1930s Singer and Nicolson Write a summary for each of the models above -How was Davson-Danielli model falsified using the following methods: 1.Freeze-etched electron micrographs 2.Structure of membrane proteins 3.Fluorescent antibody tagging

Membrane structure Describe the structure of a phospholipid bilayer Analyse models of membrane structures Describe the falsification of the Davson-Danielli model Describe how membrane proteins are diverse Draw the fluid mosaic model of membrane structure Explain the role of cholesterol in membranes

Membrane proteins Phospholipid bilayer forms a barrier so molecules cannot move through easily Almost all other functions carried out by proteins in the membrane

Membrane proteins -Hormone binding sites -Immobilized enzymes -Cell adhesion to form tight junctions -Cell-to-cell communication -Channels for passive transport -Pumps for active transport

Integral proteins Hydrophobic parts embedded in hydrocarbon chains Many are transmembrane with hydrophilic parts projecting next to phosphate heads

Peripheral proteins Hydrophilic Not embedded in the membrane Attached to an integral protein or outside of membrane (anchored with a hydrocarbon chain)

Membrane structure Describe the structure of a phospholipid bilayer Analyse models of membrane structures Describe the falsification of the Davson-Danielli model Describe how membrane proteins are diverse Draw the fluid mosaic model of membrane structure Explain the role of cholesterol in membranes

Fluid mosaic model Draw your own fluid mosaic model Include -Phospholipid bilayer -Integral proteins -Peripheral proteins -Cholesterol Take your time Do in 2D not 3D Page 31 has a good simple version

Membrane structure Describe the structure of a phospholipid bilayer Analyse models of membrane structures Describe the falsification of the Davson-Danielli model Describe how membrane proteins are diverse Draw the fluid mosaic model of membrane structure Explain the role of cholesterol in membranes

Cholesterol Animal cell membranes also contain cholesterol as well as phospholipids and proteins Type of lipid belonging to steroids Mostly hydrophobic Hydroxyl group is hydrophilic Positioned between phospholipids in the membrane

Cholesterol

Role of cholesterol Find out the function of cholesterol in the membrane Where is there more cholesterol in membranes?