B1.1.12 & B1.1.13 Formation of phospholipid bilayer + Steroids

phospholipid bilayer

a double-layered, selectively permeable membrane that forms the main structure of cell membranes

describe the process of how the phospholipid bilayer forms

the phospholipids form a double layer where the hydrophobic tails face inwards and the hydrophilic heads face outwards to the water on either side

how does the amphipathic nature of phospholipids affect phospholipid bilayer formation?

hydrophobic tails repel water and therefore move towards the middle, while hydrophilic heads are attracted to water and will move to face the water

steroids

a distinct class of lipids identifiable by its unique structure

list the identifiable features of steroids

• four fused rings of carbon atoms

• three cyclohexane rings and one cyclopentane ring

• 17 carbon atoms in total in the rings

how/why are steroids able to pass through the phospholipid bilayer?

steroids are mostly hydrocarbon and therefore are hydrophobic - this allows them to freely diffuse through the phospholipid bilayer and enter/leave cells