BIOL 1441 1st Edition Lecture 19 Outline of Last Lecture I Light properties II Photosynthetic pigments III Spectrophotometer IV Accessory pigments V Excitation of chlorophyll VI Photosystems VII Light reaction VIII Linear electron flow IX Calvin cycle dark rxn Outline of Current Lecture I The Cellular Internet II Cell Contact a Direct b Indirect local vs long distance III Reception a Types of receptors b G proteins c Tyrosine Kinases These 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 Channel IV Transduction a Protein Kinases b Protein Phosphatases c Phosphorylation cascade d Second messengers e Cyclic AMP f V Calcium ions and IP3 Response a Cytoplasm b Nucleus Current Lecture I II The Cellular Internet a Cell to cell communication essential for multicellular organisms i Coordinate their activities b Biologists discovered universal mechanisms of cellular regulation evolutionary conserved almost the same i All species bacteria flatworm fly humans ii Embryonic development iii Cancer iv Dilation of blood vessels Cell contact a Direct Cell Contact always local cells are touching i Plants animals cell junctions connect cytoplasm 1 Animals gap junctions 2 Plants plasmodesmata ii Contact between membrane bound cell surface molecules Cell cell recognition 1 Like white blood cells b Indirect Contact Local cells are not touching i Chemical messengers travel short distances ii Growth factors activate cells grow and divide iii Paracrine signaling next to each other III iv Synaptic signaling nervous system when neuron meets another cell c Indirect contact Long Distance i Plants and animals use hormones for long distance signaling ii Endocrine signaling endocrine system releases hormones 1 Travel through blood stream 2 Plants diffuse hormones as a gas Reception detect signal a Ligand signaling molecule binds to a specific receptor on target cells i Fit is similar to an enzyme and its substrate b Ligand binds receptor induces a change in shape c Shape change can do two things i Activate receptor enable it to interact with other cellular molecules ii Aggregate 2 or more receptors which then activate them 1 Causes two of them to clum together d Types of Receptors i Extracellular receptors outside of the cell in the plasma membrane membrane receptors 1 Ligands water soluble too big to pass through the membrane polar 2 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 receptors b Receptor tyrosine kinases c Ion channel receptors ii Intracellular receptors inside of the cell cytosol or nucleus 1 Ligands hydrophobic small readily pass through membrane nonpolar 2 Located in cytosol or nucleus of target cells 3 Nitric oxide gas very small 4 Steroid and thyroid hormones hydrophobic signal molecules 5 What biological molecule are they composed of iii G protein linked receptors 1 Plasma membrane receptor that works with the help of a G protein 2 Smell sight 3 Cholera botulism pertussis whooping cough produce toxins interfere with G proteins 4 G Proteins on off switch a GDP is bound to the G protein the G protein is inactive b GTP is bound G protein is active c Ligand activates the receptor which attaches to G protein and knocks off GDP GTP activates G protein IV d G protein binds enzyme and activates it e G protein acts as an enzyme and chops off own phosphate to become GDP G protein is inactive and leaves enzyme iv Tyrosine Kinases 1 Membrane receptors that attach phosphates to tyrosine amino acid 2 Tyrosine kinase receptor can trigger multiple signal transduction pathways at once 3 Enzymatic activity kinase 4 Kinase enzyme that catalyzes the transfer of phosphate groups 5 Steps a 2 inactive membrane receptors b Each have intracellular tail containing multiple tyrosines c 2 signal molecules must bind d Induces the 2 receptors to associate closely with each other form a DIMER dimerization e Dimerization partially activates the tyrosine kinase region of each receptor f Each tyrosine kinase adds a phosphate from ATP to tyrosine on the tail of the other receptor fully activatedPHOSPHORYLATION 6 Tyrosine Kinase receptors a More than 1 signal pathway can be triggered at once b Regulate and coordinate many cellular processes at once i Growth ii Reproduction iii Repair c Ability to trigger multiple pathways key difference from Gprotein coupled receptors v Ligand Gated Ion Channel 1 Ligand signal molecule 2 Membrane receptor acts as a gate when the receptor changes shape 3 Signal molecule binds the receptor the gate allows specific ions through a channel in the receptor 4 Nervous system Transduction a Molecular interactions relay signals from receptors to target molecules in a cascading effect b Usually involves multiple steps amplify signal i A few molecules can produce a large cellular response c Multistep pathways provide more opportunities for coordination and regulation d Protein Kinases activate i Enzyme transfers phosphate groups get the phosphate from ATP ii Most act on proteins different from themselves iii Most phosphorylate serine or threonine iv Each phosphorylation brings about a conformational change phosphate group interaction with charged or polar amino acids e Protein Phosphatases deactivate i Enzymes rapidly remove phosphates from proteins ii Dephosphorylation inactivates protein kinases iii Turn off the signal transduction pathway when initial signal is no longer present iv Also make protein kinases available for reuse 1 Cell can respond to the next signal v BALANCE active kinases and active phosphatases f Phosphorylation Cascade i Ligand signal molecule binds receptor ii Receptor activates relay molecule G protein adenylyl cyclase 2 nd messenger this step varies depending on receptor type iii Relay molecule activates a protein kinase 1 PK 1 Activation is adding a phosphate group 2 Adding a phosphate group induces a SHAPE CHANGE iv Pk 1 activates pk 2 1 PK 1 is dephosphorylated by a phosphatase v Pk 2 activates pk 3 1 PK 2 is dephosphorylated by a phosphatase vi PK 3 activates protein which induces cellular response Second Messengers g 2nd messengers i 2nd messengers are small nonprotein water soluble molecules or ions INSIDE the cell 1 Spread through cell by diffusion 2 Intracellular environment is aqueous ii Extracellular signal molecule ligand that