State that plasma (cell surface) membranes are partially permeable barriers. Outline the roles of membranes within cells and at the surface of cells. © Pearson Education Ltd 2008 This document may have been altered from the original Week 3
What are the functions of cell membranes?
Separate cell contents from the external environment Separating cell components from cytoplasm Cell recognition and signalling Holding the components of some metabolic pathways in place Regulating the transport of materials in and out of cells
Cell membranes are made of phospholipids. What is a phospholipid?! Phospholipids are made from triglycerides or fats Remember back to GCSE: Fats are digested to fatty acids and glycerol, therefore that is what they must be made from.
Structure of Glycerol and Triglyceride Fatty acid chains are joined to glycerol by “Condensation Reactions” These result in the formation of “Ester Bonds” We will cover this later in the course! Don’t panic
Phospholipids In a phospholipid one of the three fatty acids in a triglyceride is replaced by a phosphate group See page 16 in your text book
If phospholipid molecules are put into water they interact with the water molecules to produce a single layer orientated as in the diagram In a phospholipid molecule the phosphate head is attracted to water molecules (Hydrophilic) The fatty acid tail is repelled by water molecules (Hydrophobic)
A phospholipid bilayer produced by mixing phospholipid into water © Pearson Education Ltd 2008 This document may have been altered from the original Week 3 Hydrophilic Heads attracted to the water molecules Hydrophobic Tails repelled by water molecules, so tucked inside
Describe the fluid mosaic model of membrane structure. Describe the roles of the components of the cell membrane, including phospholipids, cholesterol, glycolipids, proteins and glycoproteins. Outline the effects of changing temperature on membrane structure and permeability. © Pearson Education Ltd 2008 This document may have been altered from the original Week 3
The fluid mosaic model of cell membrane structure You have 15 seconds to remember as much as possible! © Pearson Education Ltd 2008 This document may have been altered from the original Week 3
Homework! Find animations of cell membrane structure and function on the internet to help you to understand and remember the components of the cell membrane!
Explain the term ‘cell signalling’. Explain the role of membrane-bound receptors as sites where hormones and drugs can bind. © Pearson Education Ltd 2008 This document may have been altered from the original Week 3