membrane structure and transport across membranes Flashcards
describe the structure and properties of phospholipids
- the phosphate head of the molecule is polar so it attracts other polar molecules (hydrophillic)
- fatty acid tail is non polar so repel polar molecules (hydrophobic)
-when added to water phospholipids become arranged with no contact between the hydrophobic tails and water
explain why phospholipids form a bilayer in cell membranes
- when water is added to phospholipids they may form a layer they may form a layer on the surface with their hydrophobic tails directed out of the water
-cells have an aqueous cytoplasm and are surrounded by aqueous tissue fluid
-so phospholipids will form a bilayer so there are no exposed hydrocarbon chains
list other components of cell membranes and give a function for each
-channel proteins have water filled pores which polar molecules and ions can diffuse through
-glycolipids maintain cell stability
-glycoproteins recognises another cell as familiar or foreign
-carrier proteins helps in facilitated diffusion as an ion or molecule can bind onto the specific site on the protein, the protein changes shape and the ion or molecule can cross the membrane
-cholesterol helps to regulate the cell membranes fluidity
explain why the cell membrane is called a fluid mosaic model
some of the proteins are fixed within the membrane and others can move around within the phospholipid bilayer
explain how the level of cholestorol affects membrane fluidity
it affects the movements of the phospholipids when the temperature isnt optimal (not sure)
explain how saturated and unsaturated phospholipid tails affect membrane fluidity
kinks in unsaturated phopholipid tails help to maintain fluidity
guve reasons why the 3 layer protein lipid sandwich theory of membrane structure was rejected as a model
it doesnt allow the hydrophillic heads of the phospholipids to be in contact with water or hydrophobic tails to be kept away
