Name the three ways in which phospholipids move within the plasma membrane. Which movement is energetically unfavorable and why? a. b. c.

Phospholipids can move within the plasma membrane in the following three ways: a. **Lateral diffusion**: This is the movement of phospholipids within the same layer of the membrane. It is a common and energetically favorable movement, as it does not require the phospholipid to cross the hydrophobic core of the bilayer. b. **Flexion**: This refers to the bending of the fatty acid tails of the phospholipids. This movement is also energetically favorable and occurs frequently as the tails can move freely within the bilayer. c. **Transverse (or flip-flop) movement**: This is the movement of a phospholipid from one layer of the bilayer to the other (from the inner leaflet to the outer leaflet or vice versa). This movement is energetically unfavorable because it requires the hydrophilic head of the phospholipid to pass through the hydrophobic core of the membrane, which is energetically costly. This process often requires the assistance of enzymes called flippases or floppases to facilitate the movement.