Chapter 9 - Cell membrane and transport processes

Fluid mosaic model of the cell membrane

The fluid mosaic model describes membranes as a double layer of lipids (a lipid bilayer), which can flow and change shape, with specialised protein molecules embedded in various patterns

Movement of materials across membranes

factors that affect exchange of materials across membranes include

▪ the surface area to volume ratio of the cell

▪ concentration gradients

▪ the physical and chemical nature of the materials being exchanged

Cell membrane functions

•the recognition of other cells,

•the transportation of materials into and out of the cell – it is selectively permeable

•the provision of attachment sites for enzymes and hormones

where do unicellular organisms live?

often live in dynamic environments, such as freshwater ponds, where conditions may change quickly therefore must control the movement of substances across their cell membrane to cope with rapid changes like these.