BIOL 1441 1st EditionExam # 3 Study Guide Lectures: 19-25Lecture 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 distance2. 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 hormones4. 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 synapse5. What is an example of long distance indirect signaling? - Endocrine signaling: releases hormones that travel through the blood stream/diffuse into a gas in plants6. What are the three stages of cell signaling?- Reception: detects signal- Transduction: passes signal along (inside cell)- Response: activation of cellular response7. What kind of receptor will a hydrophobic ligand bind and why?- Intracellular- because they are small and can readily pass the membrane8. What kind of receptor will a hydrophilic ligand bind and why?- Extracellular- because they are water-soluble9. Name an example of a hydrophobic and a hydrophilic ligand. - Hydrophobic- nitric oxide, steroid hormones- Hydrophilic- adrenaline10. 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 changesthe 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 again11. What deactivates the G-protein?- G protein- it hydrolyzes (chops off) phosphate to make GTP into GDP12. What are the four steps of tyrosine kinase receptor signaling?- 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 tyrosineand goes through a structural change that activates the proteincellular response13. When are the tyrosine kinase receptors partially activated? Fully activated?- Partially-during dimerization- Fully-after they phosphorylate eachother14. Why are there multiple steps in transduction pathways?- It amplifies the signal/provides coordination and regulation15. What is the difference between kinases and phosphatases?- Kinases: “activate” enzymes that transfer phosphate groups- Phosphatases: “deactivate” enzymes that rapidly remove phosphates from proteins16. Most kinases phosphorylate which two amino acids?- Serine or threonine17. Why is protein dephosphorylation so important?- Turns off the signal in the pathway/makes kinases available for reuse18. What is specifically meant by “activation” during transduction?- Proteins are “activated” when they are phosphorylated by a kinase, which induces a SHAPE CHANGE.19. What is a second messenger? Give 3 examples.- Other molecules in the pathway that are NOT proteins- cAMP, calcium ions, IP320. 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 AMP21. 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 IP3 –gates calcium channel in the ER membrane which causes it to open- Calcium ions flow out of the ER which raises the Ca2+ level in the cytosol- Calcium ions activate the next protein in one or more pathways22. 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 cytosol23. What is the ligand that opens the calcium gated ion channel?- IP324. 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 ER25. What kind of cellular responses occur in the cytoplasm? The nucleus?- Cytoplasm: metabolism changes or open/close ion channels- Nucleus: gene transcription26. How can the same ligand induce different responses in different cell types?- Binds to different receptors- Different signal molecules in the cascade during transduction27. What type of protein can make cell signaling more efficient?- Scaffolding proteins-large relay proteins that several other relay proteins are simultaneously attached28. 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) cells2. What phase do the cells spend the most time in?- Interphase 3. What kind of cells does mitosis result in?- Two genetically identical daughter cells4. What are chromosomes?- DNA strands tightly wound around positively charged proteins-histones5. What charge does DNA have? Why?- Negative/because of its phosphate backbone6. What is chromatin?- The state that