VCU BIOL 218 - Final Exam Study Guide (6 pages)

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Final Exam Study Guide

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Final Exam Study Guide


Chapters 16, 18 & 20

Study Guide
Virginia Commonwealth University
Biol 218 - Cell Biology
Cell Biology Documents
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Biol 218 1st Edition Final Exam Study Guide Chapter 16 Delta inhibitory signal Differentiates cells from one another signal received by notch Trimeric 3 protein subunits alpha beta gamma Play role in activating G protein Receptor stays active while signal is bound amplification Viagra sildenafil citrate Blocks PDE5 phosphodiesterase type 5 used to break down cGMP prolonged relaxation of smooth muscle If cGMP isn t broken down then it causes the widening of vessels leading to an erection Remember that prolonged signal prolongs its action Signaling Cascades formed by protein kinases tyrosine or serine threonine 1 Relay 2 Transduce amplify 3 Integrate 4 Distribute Ion Channel Coupled receptors Work when flow of ions across plasma membrane changes the membrane potential also produces an electric current Examples neurotransmitters at postsynaptic membrane Enzyme Coupled Receptors Either act as enzymes or associate with enzymes inside the cell Methods o Dimer activates catalytic domain o Signal molecule binds results in activated associated enzyme G protein coupled receptors activates membrane bound trimeric GTP binding proteins Process signal molecules binds to receptor is activated unbinds from receptor and binds to enzyme to activate it Can lead to drug dependence Maintains homeostasis by desensitizing after activation o Desensitization internalization degradation recycling receptor Largest type of cell surface receptors Where vast majority of drugs work 1 2 Are ancient because they are even found in bacteria There are more than 700 in humans and more of them are orphan receptors Essential signaling molecule is beta arrestin G1 inhibitory blocks G1 Associated with pertussis toxin whopping cough G protein targets ion channel Results in immediate change in state and behavior of cells These channels are regulated by polarization which inhibits electrical excitability Example used to slow down heartbeat o Acetylcholine is released and binds to GPCR on heart pacemaker cells slower hear muscle contractions because K ion channel opens polarization of membrane G proteins target membrane bound enzymes G proteins activate these enzymes o Activated alpha subunit of G protein binds to enzyme activated enzyme production of additional intracellular signaling molecules alongside extracellular signals Intracellular adenylyl cyclase and phospholipase C cAMP second messenger signaling molecule Generated by adenylyl cyclase in cytoplasm Stimulate protein kinase A PKA so that it will carry on cellular effects Degraded by cAMP phosphodiesterase Is water soluble to allow movement through cytoplasm and nucleus Serine threonine protein kinase Gs stimulatory cholera toxin Blocks Gs which causes prolonged stimulation of gut Stimulates production of cAMP Fast pathway would take microseconds Process active GPCR active G protein adenylyl cyclase binds cAMP activates PKA metabolic kinase cell effects Example adrenaline stimulates glycogen breakdown in skeletal muscle Slow pathway could take days or more Process active GPCR active G protein adenylyl cyclase binds active PKA nucleus transcription factor cell effect Example cAMP can mediate signals from membrane to effect gene expression Phospholipase C PLC Membrane bound Produces IP3 inositol triophosphate diacylglycerol by cleaving membrane protein Process GPCR activated activated PLC activates IP3 DAG MAP kinases Activated by Ras influences protein activity gene expression Process RTK Ras binds MAPKKK MAPKK MAPK protein activity gene expression Questions What effects cell differentiation during development Signals which can also induce different responses on different target cells What regulates transcription directly Hydrophobic hormones Examples cortisol estradiol thyroxine testosterone How does the G protein turn off Switches itself off by hydrolyzing GTP 1 Activated alpha subunit activates target protein 2 Hydrolysis of GTP by subunit inactivates the subunit causes it to disassociate from target protein 3 Inactive alpha reassembles with beta and gamma complex to reform inactive G protein 4 Inactive target protein G protein How is homeostasis maintained By signaling cascades feedback regulation Why are drugs so effective They are exogenous affect cell surface receptors because they are structurally similar to proteins made inside body endogenous How do signaling molecules increase the diversity of cellular response By interacting with more than one type of receptor Example acetylcholine 1 Ion channel receptor in skeletal muscle caused more contractions 2 G protein coupled receptor in heart cells decrease in rate and force of contractions What are the effects of different ligands acting on the same receptor Cause different subtypes of G proteins to be activated in different amounts which leads to different effects Chapter 18 Critical checkpoints molecular brakes Ensure each phase of cell cycle is completed properly before starting next phase Must have DNA replication before mitosis G1 comes before S phase Cell grows and makes proteins S phase part of interphase Where chromosomes are copied Long thin and tangled thread of DNA that is not easily distinguishable with light microscope Loose to allow access for replication Occupy different specific territories in nucleus not all mixed Takes 8 hours Heterochromatin on edges and nucleolus with genes G2 comes before m phase Cell prepares to divide gap phase where cell grows and makes proteins M mitosis Phase where growth stops and cell divides DNA is dense compact and easily visual Occurs after G2 Most m Cdk activity G1 S checkpoint initiated after DNA damage Allows cell to repair damage before DNA is copied Are there sufficient nutrients and growth factors Intra S checkpoint initiated by DNA damage Slows DNA replication Does replication need to be slowed in order to fix DNA damage G2 M Checkpoint Stops cell to allow repair prior to chromosome segregation and mitosis Are all chromosomes properly attached to mitotic spindle Is all DNA damage repaired CDK s cyclins made during interphase Kinases of cell cycle control system Activated al appropriate times the quickly deactivated Must bind to regulatory cyclin proteins to be activated phosphorylates proteins Activated by cyclin activity cyclin Cdk complex Triggers entry into S or M phase Highly conserved through evolution Cyclin Cdk complex checks balances Formed in response to extracellular signals saying it s time to divide Must have cyclins bind to Cdk to make them

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