When messages are received on the cell's surface, secondary messengers relay those messages to target molecules within the cell to create a response. One important intracellular signaling cascade is the inositol triphosphate diacylglycerol or IP3/DAG pathway. On the cell surface hormones and neurotransmitters bind to G-protein coupled receptors that activate an enzyme, such as phospholipase C. This enzyme hydrolyzes, or breaks down with water, the inner layer of the phospholipid bi-layer yielding two second messengers, DAG and IP3. DAG remains in the plasma membrane to recruit protein kinase C, while IP3 diffuses through the cytoplasm and binds to IP3 receptors on the endoplasmic reticulum causing calcium ions to be released into the cytoplasm. These calcium ions bind to and activate the protein kinase C, which phosphorylates other intracellular proteins resulting in a cellular response.