HELPPP To get you thinking scientifically about what happens when you lean against the wall, try the following exercise. Imagine that you hold an empty pitcher and begin filling it with water. You try to keep the pitcher steady as it fills with water. in which direction will it feel like the picture is trying to move as it fills? Explain.

The human eye contains a molecule called 11-cis-retinal that changes shape when struck with light of sufficient energy. the change in shape triggers a series of events that results in an electrical signal being sent to the brain that results in vision. the minimum energy required to change the conformation of 11-cis-retinal within the eye is about 164 kj/mol.