Or some types of pumps can also actually absorb light energy. So we have these pumps that utilize energy to move ions and molecules across a membrane. And they use energy because they have to move them against the electrochemical gradient from a low potential to a high electric potential. And so these pumps are known as active transport as they use these ATP molecules and energy to actively move these molecules against their electrochemical gradient. Now, there are two types of membrane proteins. We have two types of membrane pumps.