Chapter 11 Wednesday November 4 2015 8 04 AM Cell Signaling Ion channel Receptors Important in the nervous system Lead to changes in sodium and calcium signal 1 Signal molecule ligand binds onto ligand gated ion channel receptor within the plasma membrane layer o Channel has a gate that is closed o Ions floating outside of plasma membrane 2 Gate opens after o Ions go through channel o Ions get through to the cell cellular response o Initiates the transection state Open or close in response to a chemical signal 3 Gate closes o Transient not lasting forever Two locations cell membrane and few of them are located inside the cell Intracellular receptors Intracellular Receptors Located within the cell Requires signal molecules to go into the cell Small nonpolar hydrophobic molecules Ex Testosterone Can diffuse through the phospholipid bilayer Once in the cytosol Binds to receptor protein Binding changes the conformation of the receptor protein to be recognized by nuclear pore complex Allow protein to be imported Act as transcriptional factor Turns on and off transcriptions for DNA mRNA is transcribed Transported out of nucleus and translated into proteins Signal molecules first messenger Second messengers Certain small molecules and ions are key components of signaling pathways o Cyclic AMP Based on the structure of AMP Modified AMP o Calcium ions and inositol Triphosphate Cyclic AMP Acts as a second messenger Produced from ATP by the enzyme adenylyl cyclase o Enzyme catalyze the production of AMP from ATP Phosphodiesterase o Breaks covalent bond between oxygen and carbon o Return cyclic AMP to regular AMP Q Adenylyl cyclase has the opposite effect of a Phosphodiesterase b cAMP c Tyrosine Kinase receptor d GPCR e calcium At time 0 seconds serotonin At time 20 seconds Produced and quickly spread from the new cell cAMP levels 20 seconds after serotonin treatment Calcium Ions and Inositol Triphosphate Maintain low calcium concentration o Calcium pumps on membrane o Calcium pumps on ER o Calcium pumps on mitochondria So oriented that they pump Cytosol has low calcium concentration Q Which is not a second messenger a cAMP b Calcium c IP3 d Epinephrine first messenger stops at cell membrane e None of the above 1st messenger binds to receptor GPCR activates G protein GTP Activates its enzyme phospholipase C Once activated PC it will scan the membrane and find a special lipid POP2 and cut off the IP3 from the membrane lipid IP3 is a second messenger small molecule that can quickly diffuse through the cell IP3 diffuses out the cell o Calcium channel CA2 second messenger o Diffuse from higher to lower concentration Lumen to cytosol o Calcium diffuse through to bring about cellular responses Can be done by tyrosine An inhibitor of which factor could be used to block the release of Ca from the ER o If we block IP3 or G protein first messengers epinephrine phospholipase C direct one calcium channel we can block the release GPCR turn off tyrosine kynase receptor we also block the calcium release Nuclear Response Phosphorylation cascade Where they will phosphorylate Bind to DNA and activate gene mRNA Q Which of the following will most likely to be an immediate effect of growth factor binding to receptor a Protein kinase activity b GTPase acitvity haven t been discussed c Photophotase activity haven t been discussed opposite of kinase remove phosphate group from adenylyl d Adenylyl cyclase activity e Phospholipase activity not activated by growth hormone Mitosis Within mitosis cell takes a lot of time Goes to M phase division of nucleus Cytokinesis In animal cells o Cytokinesis occurs by a process known as cleavage forming a cleavage furrow to separate cytoplasm o Cell membrane pinches inside to form a furrow deeper and deeper until it separates into two daughter cells Cellular kinesis is different between animal cells and plant cells Plant cells o Mitosis Prophase chromatin is condensing nucleolus is beginning to disappear mitotic spindle starting to form Prometaphase nuclear envelope will fragment discrete chromosomes consisting of two identical sister chromatids spindle fibers attach Metaphase all chromosomes lined in equator of cell no nucleolus envelop visible spindle is complete chromasomes Anaphase kinetochore microtubele fibers shorten split Telephase reverse of prophase reappearing of nucleolus Deliver cell wall material to form cell plate o During cytokinesis A cell plate forms Carbohydrates are deposited to the middle of the cell to form the cell plate as the plate grows it completely separates mother cell into two daughter cells the plate becomes the new cell wall Q A cell with 92 chromosomes at metaphase of mitosis at the end of telophase there will be 2 nuclei with chromosomes each a 92 chromosomes are x shaped two sister chromatids doubles the number of chromosomes at anaphase cells should have 184 telephase evenly divides into two nuclei 92 b 46 c 23 d 16 e 184 Q If there are 20 chromatids in the cell at metaphase how many chromosomes will each daughter cells have after mitosis a 20 b 10 at metaphase x shape 2 chromatids after mitosis stelephase and cytokinesis the amount should be the same c 30 d 5 e 40 Q Which of the following occurs during mitosis a Uncoupling of the chromatids at centromere anaphase b Synthesis of DNA S phase of interphase c Synthesis of protein G2 some cells also during G1 if main task is making insulin endocrine cell d Separation of cytoplasm cytokinesis e Formation of cell plate cytokinesis of plant cell Binary Fission Prokaryotes Bacteria Binary fission o The bacterial chromosome replicates o The two daughter chromosomes actively move apart Repel each other move towards opposite poles They are separated as they are synthesized Cell cycle control internal factors o The frequency of cell cycle varies from cell to cell o Determine when and how fast the cell can divide Evidence for Cytoplasmic Signals o Molecules present in the cytoplasm Regulate progress through the cell cycle The Cell cycle control system o The sequential events of the cell cycle Are directed by a distinct cell cycle control system which is similar to a clock At checkpoints The clock has specific checkpoints where the cell cycle stops until a goahead signal is received Without a signal the G1 phase exits the cell cycle and goes into G0 phase a non dividing state The Cell Cycle Clock Cyclins and Cyclin Dependent Kinases o Two types o No cyclin they are inactive The Cell Cycle Clock o The