Cell Communication

1. Cell Communication

2. Its Importance The role of celluar communication is extremely critical in our lives Absolutley essential for multicellular organism such a humans The trilllions of cells in a multicellular organism must communicate with each other to cordinate their activities in a way that enables the organism to develop from a zygote,then survive and reproduce (meiosis &mitosis)

3. How Does this Happen • A signal- tranduction pathway is a series of steps by which a signal on a cell surface convert into a cellular response • 3 main steps: Reception, Transduction and Response • Animal may communicate by: a. Gap junction b. cell-cell recognition

4. Communicating Gap Junction Cell-cell Recognition • Cell junction(a type of structure that exists within the tissue of a multicellular organism) directly connect the cytoplasm of adjacent cells • Signaling substances dissolve in cytosol can pass freely between adjacent cells • Two cells may communicate be interaction between molecules protruding from their surfaces

6. Local & Long Distance Local Long distance • Messenger molecules ,ligand, are secreted by the signaling cell • Local regulators influence cells in the surroundings • Types of local signalling: -Paractrine signalling: secreting cell acts on nearby target cells by discharging molecules of a local regulator (a growth factor, for example) -Synaptic signaling: a nerve cell releases neurotransmitter molecules into a synapse (the narrow space between the nerve cell) ,stimulating the target • Hormone signaling: -specialized cells release hormone molecules in vessels of the circulatory system, by which they travel to target cells in other part of the body - plant hormones, growth regulators, travel in vessels but more often reach their target by moving through cells or by diffusion through air as a gas

8. Reception • Signal molecule binds to a receptor protein causing it to change shape • Most signal receptors are plasma membrane proteins, some are found in the cytosol or the nucleus of target cells • Different kinds of cell have different collections of proteins, which gives each kind of cell specificity in detecting and responding to signal • 3 main type of membrane receptors: -G-protein-linked receptor: plasma membrane receptor that works with the help of g protein -Receptor tyrosine Kinase: membrane receptors that attach phosphate to tyrosine; can trigger multiple signal transduction pathways at once -Ion Channel Receptor: acts as a gate when the receptor changes shape; when a ligand binds to receptor, the gate allows specific ions (Calcium) through a channel in the receptor

9. G-Protein

10. Tyrosine Kinase

11. Ion Channel

12. Transduction • Cascade of molecular interactions relay signals from the receptor to target molecules in the cell • involves multiple steps, which provide more opportunities for coordination and regulation • Scaffolding proteins are large relay proteins to which other relay proteins are attached,this increase the signal transduction efficiency • In many pathways the signal is transmitted by a cascade of protein phosphorylation; phosphatase enzyme remove phosphate and add phosphate ,this system acts ass a molecular switch, turning on activities and off

13. Response • Cell signalling leads to regulation of the cytoplamic activities or transcription , “out put response”. • Ultimatly ,a signal transduction pathway leads to regulation of one or cellular activities • The response action may occur in the cytoplasm or may involve in the nucleus ,many involve the activity of enzymes