BIOL 1441 1st Edition Lecture 19 Outline of Last Lecture I. Light propertiesII. Photosynthetic pigmentsIII. Spectrophotometer IV. Accessory pigmentsV. Excitation of chlorophyllVI. PhotosystemsVII. Light reactionVIII. Linear electron flowIX. Calvin cycle-dark rxnOutline of Current Lecture I. The Cellular InternetII. Cell Contacta. Directb. Indirect-local vs. long distanceIII. Receptiona. Types of receptorsb. G proteinsc. Tyrosine KinasesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.d. Ligand-Gated Ion ChannelIV. Transductiona. Protein Kinasesb. Protein Phosphatasesc. Phosphorylation cascaded. Second messengerse. Cyclic AMPf. Calcium ions and IP3V. Responsea. Cytoplasmb. Nucleus Current LectureI. The Cellular Interneta. Cell-to-cell communication essential for multicellular organismsi. Coordinate their activitiesb. Biologists discovered universal mechanisms of cellular regulation (evolutionary conserved)-almost the samei. All species- bacteria, flatworm, fly, humansii. Embryonic developmentiii. Canceriv. Dilation of blood vesselsII. Cell contacta. Direct Cell Contact- always local- cells are touchingi. Plants & animals cell junctions connect cytoplasm1. Animals: gap junctions2. Plants: plasmodesmataii. Contact between membrane bound cell-surface molecules “Cell-cell recognition”1. Like white blood cellsb. Indirect Contact- Local- cells are not touchingi. Chemical messengers travel short distancesii. Growth factors- activate cells grow and divideiii. Paracrine signaling: next to each otheriv. Synaptic signaling: nervous system-when neuron meets another cellc. Indirect contact- Long Distancei. Plants and animals use hormones for long distance signaling ii. Endocrine signaling- endocrine system releases hormones1. Travel through blood stream2. Plants- diffuse hormones as a gasIII. Reception- detect signala. Ligand (signaling molecule) binds to a specific receptor on target cellsi. Fit is similar to an enzyme and its substrateb. Ligand binds receptor- induces a change in shapec. Shape change can do two things:i. Activate receptor- enable it to interact with other cellular moleculesii. Aggregate 2 or more receptors- which then activate them1. Causes two of them to clum togetherd. Types of Receptorsi. Extracellular receptors- outside of the cell, in the plasma membrane (membrane receptors)1. Ligands- water soluble, too big to pass through the membrane, polar2. Water-soluble signal molecules bind to specific sites on receptors in the plasma membrane (hydrophilic, polar!)3. There are 3 main types of membrane receptors:a. G-protein-linked receptorsb. Receptor tyrosine kinasesc. Ion channel receptorsii. Intracellular receptors- inside of the cell, cytosol or nucleus1. Ligands- hydrophobic, small, readily pass through membrane, nonpolar2. Located in cytosol or nucleus of target cells3. Nitric oxide- gas, very small4. Steroid and thyroid hormones hydrophobic signal molecules5. What biological molecule are they composed of?iii. G-protein linked receptors1. Plasma membrane receptor that works with the help of a G protein2. Smell, sight3. Cholera, botulism, pertussis (whooping cough)- produce toxins interfere with G proteins4. G-Proteins- on/off switcha. GDP is bound to the G protein, the G protein is inactiveb. GTP is bound, G protein is activec. Ligand activates the receptor, which attaches to G protein and knocks off GDP. GTP activates G proteind. G protein binds enzyme and activates ite. G protein acts as an enzyme and chops off own phosphate to become GDP= G protein is inactive and leaves enzymeiv. Tyrosine Kinases1. Membrane receptors that attach phosphates to tyrosine (amino acid)2. Tyrosine kinase receptor can trigger multiple signal transduction pathways at once3. Enzymatic activity- kinase4. Kinase- enzyme that catalyzes the transfer of phosphate groups5. Steps:a. 2 inactive membrane receptorsb. Each have intracellular tail containing multiple tyrosinesc. 2 signal molecules must bindd. Induces the 2 receptors to associate closely with each other form a DIMER-dimerization e. Dimerization partially activates the tyrosine-kinase region of each receptorf. Each tyrosine kinase adds a phosphate from ATP to tyrosine on the tail of the other receptor, fully activated- PHOSPHORYLATION6. Tyrosine Kinase receptors:a. More than 1 signal pathway can be triggered at onceb. Regulate and coordinate many cellular processes at oncei. Growthii. Reproductioniii. Repairc. Ability to trigger multiple pathways- key difference from G-protein coupled receptorsv. Ligand-Gated Ion Channel1. Ligand- signal molecule2. Membrane receptor acts as a gate when the receptor changes shape3. Signal molecule binds the receptor, the gate allows specific ions through a channel in the receptor4. *Nervous systemIV. Transductiona. Molecular interactions relay signals from receptors to target molecules in a cascading effectb. Usually involves multiple steps- amplify signali. A few molecules can produce a large cellular responsec. Multistep pathways provide more opportunities for coordination and regulationd. Protein Kinases (“activate”)i. Enzyme transfers phosphate groups-get the phosphate from ATPii. Most act on proteins different from themselvesiii. Most phosphorylate serine or threonineiv. Each phosphorylation brings about a conformational change- phosphate group interaction with charged or polar amino acidse. Protein Phosphatases (“deactivate”)i. Enzymes rapidly remove phosphates from proteinsii. Dephosphorylation- inactivates protein kinasesiii. Turn off the signal transduction pathway, when initial signal is no longer presentiv. Also, make protein kinases available for reuse1. Cell can respond to the next signalv. BALANCE- active kinases and active phosphatasesf. Phosphorylation Cascadei. Ligand (signal molecule) binds receptorii. Receptor activates relay molecule (G-protein, adenylyl cyclase, 2nd messenger) *this step varies depending on receptor typeiii. Relay molecule activates a protein kinase #1 (PK)1. “Activation” is adding a phosphate group2. Adding a phosphate group induces a SHAPE CHANGEiv. Pk #1 activates pk #21. PK #1 is dephosphorylated by a phosphatasev. Pk #2 activates pk #31. PK #2 is dephosphorylated by a phosphatasevi. PK #3 activates protein which induces cellular responseSecond Messengersg. 2nd messengersi. 2nd messengers are small, nonprotein, water-soluble molecules or