Kaishea White
Period: 3
01.12.14
IB Biology

Cell To Cell Communication Unicellular and multicellular organisms need to sense their environment in order to survive. Unicellular organisms need to be able to differentiate between poisonous foods and to avoid predators. Cells release chemical messengers to communicate. They communicate either by paracrine signaling or gap junctions. Local signaling in animals is called paracrine signaling. While gap junction is the direct contact between cells. There are principles of cell signaling where the cells convert signals that carry information and then attach to one another. A target cell detects the signal that the cell releases during the communication of the cells. Animals have factors that contribute to their communication that include direct contact, growth factors, or neurotransmitters. The growth factors and neurotransmitters are what secrete the local regulators. Meaning that they separate the local regulators. There are 3 stages of cell signaling; reception, transduction, and response. In the first stage, reception, the target cell senses the signaling molecule in the exterior. During the second stage, transduction, the signal is converted and formed to do a specific function. The final stage, response, is where the specific function is carried out. In reception a signal molecule binds to a receptor protein and that causes it to change shape. The most important stage in the transduction of a signal is the conformational change. These receptors are found in two places, intracellular proteins and cell-surface proteins. Intracellular proteins are found I the plasma membrane of the cytoplasm or nucleus whereas the cell-surface proteins are embedded in the plasma membrane. Intracellular proteins are hydrophobic meaning that they don’t like water. In transduction the there is a signal between the receptors to the target molecule. Transduction has pathways, signal which involve a phosphorylation cascade. But the pathway has multiple steps, there are enzymes called protein kinases that help the proteins move up to another level. In response the cell signaling leads to the regulation of transcription and other things such as cytoplasmic activities. Signaling pathways interfere with protein synthesis. It can turn specific genes on or off. There are 5 different types of signaling. Multicellular organisms have four types whereas unicellular only has one.