Unit 41 Cell Membranes and Transport

Apuntes

Unit 4: Cell Membranes and Transport 4.1: Importance of Membranes Membranes are crucial to cells as they control the transport of substances in and out of the membrane. This makes them useful not only for the cell membrane but organelles as well. Other functions include: - Enable cells to receive hormonal messages. - In chloroplast they contain the pigments that absorb light. 4.2: Structure of Membranes Phospholipids Phospholipids are the most important part and the base of a membrane. Phospholipids have a hydrophilic head and hydrophobic tail. This causes them to form 2 structures when in water: - Micelles: a circular structure wil all the head facing outwards sort of protecting the tails - Bilayer: This is what membranes are made of, the heads face in two directions as the phospholipids allign themselves next to eachother in a parallel structure. The Fluid Mosaic model This model explains the structure of the membranes. The ”fluid” refers to how the phospholipids and proteins can move around by diffusion. Additionally, the fluidity of the membrane is like that of oil, The ”mosaic” refers to how the membrane looks like when viewed from above due to the scattered proteins....