Cell Biology (BIOL 4374 and BCHS 4313) Third Exam 4/24/01

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1 Cell Biology (BIOL 4374 and BCHS 4313) Third Exam 4/24/01 Name SS# This exam is worth a total of 100 points. The number of points each question is worth is shown in parentheses. For multiple choice questions, circle the correct answer. Good luck! 1. (6) Put the stages of extracellular signaling in order of occurrence from first to last. a) Detection of signal by a receptor first e b) Termination of signaling second c c) Release of signaling molecule third d d) Transport of signaling molecule to target fourth a e) Synthesis of signaling molecule fifth f f) Response of cell to signal sixth b 2. (2) G-protein linked receptors have 7 (number) transmembrane domains. 3. (2) Upon adrenalin binding, the ß-adrenergic receptor causes camp production by activating what two factors? G s protein and adenylyl cyclase 4. (2) camp kinase leads to the phosphorylation of glycogen synthetase (enzyme) to block glycogen synthesis and _glycogen phosphorylase or GP kinase_ (enzyme) to increase glycogen breakdown. 5. (2) Upon binding to ligand, the RTK class of receptors dimerize, then phosphorylate each other at tyrosine residues. 6. (2) GRB2 is an adapter protein having and SH2 domain that binds to _phosphotyrosines on RTK_ and an SH3 domain that binds to SOS. 1

2 7. (2) During RTK signaling, the GTPase switch protein Ras is activated by the guaninenucleotide exchange factor (GEF) SOS. 8. (2) The following steps are part of the kinase cascade that transmits signals from activated Ras protein except: a) MEK phosphorylates MAP kinase answer: d b) Raf phosphorylates MEK c) MAP kinase phosphorylates target proteins d) Ras phosphorylates Raf 9. (4) Phospholipase C cleaves PIP2 into IP3 and DAG. 10. (2) IP3 releases Ca+2 from what cellular compartment? Endoplasmic reticulum or sarcoplasmic reticulum 11. (2) When acetylcholine binds to muscarininc acetylcholine receptors, activation of leads to a decrease in the level of camp. answer: d a) G S b) G olf c) G t d) G i e) G q 12. (4) Insulin binds to RTK (type of receptor) on the surface of liver cells to decrease (increase or decrease) glucose in the blood stream, whereas glucagon binds to GPCR (type of receptor) on the surface of liver cells to increase (increase or decrease) glucose in the blood stream. 13. (2) Phosphorylation and endocytosis are two common mechanisms by which can be downregulated. a) Cell surface receptors b) Adenylyl cyclase c) Ras d) Phospholipase C e) camp kinase 2

3 14. (2) What second messenger pathway activates CREB transcription? answer: d a) Ca+2 b) IP3 c) DAG d) camp e) PIP2 15. (3) List thee three types of neurons. Sensory neuron, interneuron, motor neuron. 16. (2) The resting potential of an average neuron is _-60mV (-50 to 70mV is OK) (number and units). 17. (8) During the propagation of an action potential, Na + _ ions move into_ (direction) the cell due to the opening of _voltage gated Na + (ion) channels, thereby depolarizing the membrane. To repolarize the membrane, voltage gated K + (ion) channels open and K + ions flow out of (direction) the cell. 18. (2) The entire timecourse of an action potential is. answer: c a) 2 seconds b) 0.1 milliseconds c) 2 milliseconds d) 20 seconds e) 20 milliseconds 19. (2) Myelin is derived from Schwann cells and functions to insulate axons and increase impulse rate. 20. (2) The threshold potential (~-40mV) is measured at the? answer: c a) dendrites b) cell body c) axon hillock d) axon e) axon terminal 21. (2) What type of amino acids allow the S4 domain to detect changes in membrane voltage? a) basic amino acids b) acidic amino acids c) hydrophobic amino acids 22. (2) The N-terminal ball and chain is responsible for V-gated channel inactivation. What is the effect of lengthening the chain on inactivation? or c a) decreases inactivation time b) increases inactivation time c) no effect 3

4 23. (2) Which type of synapse is faster? a) electrical b) chemical 24. (2) When an action potential reaches the axon terminal it triggers the opening of voltage gated Ca +2 channels. 25. (4) The nicotinic acetylcholine receptor is found on muscle cells and is a ligand gated Na + /K + channel (type of molecule). 26. (2) GABA and Glycine act as inhibitory neurotransmitters because they activate Cl - channels that hyperpolarize the post-synaptic cell. 27. (2) Glutamate will only open NMDA receptors after partial depolarization releases blockage by a Mg +2 ion. 28. (6) Under dark conditions, photoreceptors are depolarized_ (polarized or depolarized). When light activates _rhodopsin (protein) by causing isomerization of _11-cis_ retinal to _all trans retinal, the G-protein transducin is activated. Transducin then activates cgmp phosphodiesterase (protein), which destroys cgmp and inactivates cgmp-gated Na + /Ca +2 channels, thereby causing hyperpolarization and blockage of neurotransmission. 29. (2) The ability to tune out a non-threatening stimulus that you experience frequently is called habituation. 30. (2) During classical conditioning in Aplysia, a weak touch to the siphon is the conditioned stimulus, and a blow to the head is the unconditioned stimulus. 4

5 31. (4) Name two types of cell adhesion molecules that make homophilic interactions. Cadherins and Ig like CAMs. 32. (2) During leukocyte extravasation, what is the order of cell adhesion molecule binding from the earliest event to the latest event: a) P selectin to carbohydrate, PAF to PAF receptor, α L β 2 integrin to I-CAM b) PAF to PAF receptor, α L β 2 integrin to I-CAM, P selectin to carbohydrate c) P selectin to carbohydrate, α L β 2 integrin to I-CAM, PAF to PAF receptor d) α L β 2 integrin to I-CAM, PAF to PAF receptor, P selectin to carbohydrate e) PAF to PAF receptor, P selectin to carbohydrate, α L β 2 integrin to I-CAM 33. (2) Collagen triple helices are held into fibers through crosslinks of lysine residues at their N and C termini. answer: c a) hydroxylysine b) hydroxyproline c) aldol d) ascorbic acid e) glycosaminoglycan 34. (2) Cadherins, adapter proteins and keratin intermediate filaments are part of what cell-cell junction? a) tight junctions b) desmosomes c) adherens junction d) hemi-desmosome e) gap junction 35. (2) Glycosaminoglycan polysaccharides are found on serine and threonine residues in: a) proteoglycans b) hyaluronin c)laminin d) fibronectin e) integrin 36. (2) The two ECM components that comprise the major structural elements of the basal lamina are laminin and collagen IV. 37. (3) Which Cell-Cell adhesion molecule is dependent on Ca+2? a) Integrin b) Cadherin c) N-CAM d) Fibronectin e) Hyaluronin 38. (2) Growth factors must be bound by which glycosamino glycan before they can bind to growth factor receptors? a) hyaluronin b) heparan sulfate c) chondroitin sulfate d) keratan sufate 5