BIOL 1441 1st Edition Exam 3 Study Guide Lectures 19 25 Lecture 19 March 24 1 What is the main difference between direct and indirect cell signaling Direct contact cells are touching only local Indirect contact cells aren t touching local or long distance 2 What are the two types of direct cell signaling Plants animals cell junctions connect cytoplasm Cell cell recognition contact between membrane bound cell surface molecules 3 What is the difference between local indirect signaling and long distance indirect signaling Local chemical messengers travel SHORT distances Long distance travel long distances use hormones 4 What are two examples of local indirect signaling Paracrine signaling affects cell next to it growth factors Synaptic signaling when neuron transfers neurotransmitters onto other neurons across the synapse 5 What is an example of long distance indirect signaling Endocrine signaling releases hormones that travel through the blood stream diffuse into a gas in plants 6 What are the three stages of cell signaling Reception detects signal Transduction passes signal along inside cell Response activation of cellular response 7 What kind of receptor will a hydrophobic ligand bind and why Intracellular because they are small and can readily pass the membrane 8 What kind of receptor will a hydrophilic ligand bind and why Extracellular because they are water soluble 9 Name an example of a hydrophobic and a hydrophilic ligand Hydrophobic nitric oxide steroid hormones Hydrophilic adrenaline 10 What are the four steps of G protein receptor signaling 1 G protein is bound to GDP and loosely attached to the cytoplasmic side of the membrane G protein is INACTIVE 2 Signaling molecule binds to extracellular side of receptor and activates the receptor then binds to inactive G protein causing a GTP to knock off GDP G protein is ACTIVATED 3 Activated G protein dissociates from receptor and binds to an enzyme which changes the enzyme s shape and activity which can trigger the next step 4 G protein acts as GTPase enzyme and chops off own phosphate to become GDP again leaves enzyme and G protein is INACTIVE again 11 What deactivates the G protein G protein it hydrolyzes chops off phosphate to make GTP into GDP 12 What are the four steps of tyrosine kinase receptor signaling 13 14 15 16 17 18 19 20 21 22 23 Signaling molecule binds and causes two receptor monomers to associate closely together and form a dimer dimerization Dimerization activates the tyrosine kinase region of each monomer Each tyrosine kinase adds a phosphate from an ATP molecule to a tyrosine on the tail of the other monomer Recognized by relay proteins inside cell which bind to a specific phosphorylated tyrosine and goes through a structural change that activates the protein cellular response When are the tyrosine kinase receptors partially activated Fully activated Partially during dimerization Fully after they phosphorylate eachother Why are there multiple steps in transduction pathways It amplifies the signal provides coordination and regulation What is the difference between kinases and phosphatases Kinases activate enzymes that transfer phosphate groups Phosphatases deactivate enzymes that rapidly remove phosphates from proteins Most kinases phosphorylate which two amino acids Serine or threonine Why is protein dephosphorylation so important Turns off the signal in the pathway makes kinases available for reuse What is specifically meant by activation during transduction Proteins are activated when they are phosphorylated by a kinase which induces a SHAPE CHANGE What is a second messenger Give 3 examples Other molecules in the pathway that are NOT proteins cAMP calcium ions IP3 What is the cAMP signaling pathway include activation and deactivation The first messenger activates a G protein coupled receptor which activates a specific G protein The G protein ACTIVATES adenylyl cyclase Adenylyl cyclase catalyzes the conversion of ATP to cAMP cAMP acts as a second messenger and activates another protein usually protein kinase A leading to a cellular response Phosphodiesterase DEACTIVATES cAMP by converting it into AMP What is the Ca2 signaling pathway A signaling molecule binds to a receptor which activates phospholipase C Phospholipase C cleaves PIP2 into DAG and IP3 IP3 diffuses through cytosol and binds to an IP 3 gates calcium channel in the ER membrane which causes it to open Calcium ions flow out of the ER which raises the Ca 2 level in the cytosol Calcium ions activate the next protein in one or more pathways Where is the Ca2 concentration the highest in the cell and why In the ER mitochondria because of the Ca2 pumps that pump it out of the cytosol What is the ligand that opens the calcium gated ion channel IP3 24 Is the calcium gated ion channel considered an extracellular membrane receptor or an intracellular receptor and why Extracellular receptor because it is embedded in the membrane of the ER 25 What kind of cellular responses occur in the cytoplasm The nucleus Cytoplasm metabolism changes or open close ion channels Nucleus gene transcription 26 How can the same ligand induce different responses in different cell types Binds to different receptors Different signal molecules in the cascade during transduction 27 What type of protein can make cell signaling more efficient Scaffolding proteins large relay proteins that several other relay proteins are simultaneously attached 28 Why would we want to study cell signaling in a flatworm or a mouse Cell signaling patterns are highly conserved in all organisms We can manipulate and experiment with cellular pathways in worms and mice to deduce how the same processes work in humans Lecture 20 March 26 1 What are the 2 types of cellular division Meiosis sex cells Mitosis somatic body cells 2 What phase do the cells spend the most time in Interphase 3 What kind of cells does mitosis result in Two genetically identical daughter cells 4 What are chromosomes DNA strands tightly wound around positively charged proteins histones 5 What charge does DNA have Why Negative because of its phosphate backbone 6 What is chromatin The state that chromosomes are in at all times except when the cell is getting ready to divide not visible with a light microscope 7 How many chromosomes in DNA replication 23 PAIRS of chromosomes 46 TOTAL Each pair replicates 92 TOTAL 8 What are sister chromatids Identical DNA molecules one chromosome duplicates into TWO sister chromatids 9 What is a cohesin