structure-function relationship of phospholipids

Question 1

how does being amphipathic allow phospholipids to form a lipid bilayer of membranes?

Answer 1

• it allows phospholipids to assemble into a bilayer in an aqueous environment

Question 2

how does being amphipathic allow phospholipids to form a hydrophobic boundary between the aqueous exterior & interior of the cell?

Answer 2

• it allows the hydrophilic phosphate heads of the phospholipids to face outwards & make contact with the aqueous exterior & cytoplasm of the cell
• while the hydrophobic fatty acid chains of the phospholipids can face inwards, so that they are sandwiched between the hydrophilic phosphate heads, forming a hydrophobic boundary between the aqueous exterior & interior of the cell

Question 3

how does formation of the hydrophobic core of the phospholipid bilayer act as a selectively permeable membrane?

Answer 3

• this is because only non-polar molecules can cross the phospholipid bilayer, while charged ions & polar molecules are unable to cross the hydrophobic core of the phospholipid bilayer
• hence, the hydrophobic core of the phospholipids regulate the movement of substances across the phospholipid bilayer