Ch 11.- Prokaryote and eukaryote have cellular communication. - Bacteria, protozoa, yeast are good at mass communication. Biofilm: plaque full of microorganisms to aggregate. They can exploit resources; have all kinds of activities without having stress when they aggregate in mass. Most ofthe bacteria in biofilms sense the population of how many are there. They sense how much of the local density is. - Aggregation is called: quorum sensing (how the bacteria sense the concentration of signals coming from outside. They wait and see if all of themcome before they start something. A behavior is triggered based on the population). - Local signaling: short distance signaling. Most gap junctions (plasmodesmata in cells) where chemicals go back and forth. Some also have cell recognition. - No contact but release chemicals that travel some distance. Synaptic signaling: nerve cells communicate, the area between 2 nerve cells (synapse).- Most growth factors communicate through paracrine signaling. Telling the cells to grow! - Long distance signaling: most hormones communicate this way. Hormone released in brain but response could be somewhere else. Endocrine signaling!- A particular pathway is followed by all types of signaling/communication:o Reception: a protein binds to the receptor, a series of reactions are releasedo Transduction: relay moleculeso Response: whatever the signal molecule came to do is responded. Signaling molecules are called Ligand. - Ligands bind to the receptor molecules but they’re big so cant just enter the membrane. 3 main receptor proteins!! Once the signal binds to the receptor, there’s a change and a pathway is triggered. o GPCRs: need to be activated. Whenever a G Protein needs to be activated, it uses GTP (similar to ATP). You’re trying to target GPCRs tothe host cell! o RTKs: this receptor to be active, phosphate group is added. Tyrosine (amino acid) is sitting in an inactive form until the signaling molecule attach to them forming a dimer and making them active. This leads to the phosphorylation of tyrosine. They tend to activate several transactions at a time. While GPCRs only do one at a timeo Ligand-gated ion channel: allowing ions to come in. most neurotransmitters use this! - Intracellular receptors: there are some receptors that are also inside the cell. Some would have to have any small hydrophobic molecule to help them moveinside the cell. They have some response within nucleus or in cytoplasm, they don’t need help and can come directly into intracellular area.- Phosphatases: help remove phosphate group. Kinase: help add them. The point of it to have several different responses. - Most second messengers are non polar and small. Example: cAMP. Its cyclic because the way it binds. They also target (when you keep cgmp active, it keeps blood flow active to the penis: how Viagra works). ATP is transferred tocAMP by an enzyme (look at the picture). - How is this pathway regulated? How is amplification is done? Each cell, having same signal molecule can behave differently because of different sets of protein (ligand). To make sure signal is transferred efficiently scaffolding protein is used. - Apoptosis: cell death, important in eukaryote. Some enzymes destroy cells and main one is Caspases (they cut off all the
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