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Cell Bio- Exam 3
study for final
| Question | Answer |
|---|---|
| Which of the following is/are characteristic of a receptor tyrosine kinase process? | - The signal molecule must be able to form a dimer. - Once the signal molecule has activated the kinase activity of the receptor tyrosine kinase, each molecule of the kinase reciprocally activates the other kinase molecule. |
| Lysosomes have acidic intracellular pH and channel transport solutes faster than carrier. cell whose lysosomes have both proton pump and H+ channel thinking H+ channel speeds uptake of H+ improving ability of lysosome to develop, maintain low pH. Right? | No. |
| Intracellular Ca2+ is a useful 2nd messenger because: | It is normally at a very low intracellular concentration so relatively large changes of cytoplasmic [Ca2+] can be achieved with small influxes of Ca2+ into the cytoplasm. |
| The proto-oncogene Ras is involved downstream of which general types of signaling? | Receptor tyrosine kinase enzyme linked. |
| Which of the following general types of receptors form the largest cell-surface receptor family? | G-protein linked receptors. |
| Which one of the following statements about receptor tyrosine kinase systems is TRUE? | Once the signal molecule has activated the kinase activity of the receptor tyrosine kinase, one molecule of the kinase phosphorylates the other molecule of the kinase. |
| Which of the following represents the correct sequence of events occurring during an action potential? | depolarize Vm to threshold-->Na+ channels activate--> Vm depolarizes to ~+50 mV-->Na+ channels inactivate and K+ channels open-->Vm repolarizes to normal resting potential. |
| Why do you suppose small ions and molecules like glucose cannot easily cross the lipid bilayer portion of a cell membrane? | They are too hydrophilic and so cannot easily cross the "greasy" lipid bilayer. |
| Cell which alpha-subunits of non G-P receptor activated, affinities for GDP and GTP are equal. The cytoplasmic concentration of GTP is 10X GDP leads conclude that the result is near-continuous activation of the G-binding P. Right? | Yes |
| Most cells maintain electrical potential difference across their external cell membrane such that __ side of the membrane is negative with respect to extracellular side. K+ has intracellular compartment concentration that is __ than in extracellular. | Intracellular; Greater |
| Which of the following represent ways in which a signaling cascade can amplify a signal? | By activating a protein kinase that can then phosphorylate and activate many protein molecules. |
| Ras, a small protein bound by its tail to the plasmalemma and part of nearly every receptor tyrosine kinase signaling system, is a GTP-binding protein. | True |
| The electrochemical driving force on a given charged solute molecule: | Combines the free energies available from the concentration gradient of the solute plus the electrical potential across the cell membrane. |
| Which of the following are considered to be minimal general elements for signaling? | A receptor, a transduction mechanism, an effector mechanism. |
| In nerve cell terminals, an influx of _________ causes synaptic vesicles to fuse with the pre-synaptic membrane. This fusion allows the contents of the synaptic vesicles, ________, to diffuse to the receptors on the post-synaptic membrane. | Ca2+; Neurotransmitters |
| Paracrine signals act within an extremely localized region most likely because: | - Paracrine signal molecules are very short-lived due to rapid spontaneous degradation, uptake by cells or breakdown by enzymes in extracellular space. - Diffusion of signal molecules is limited because it's bound by molecules in extracellular matrix. |
| G-protein coupled receptors are very often: | Plasma membrane-located proteins with seven transmembrane-spanning domains. |
| Which of the following is an example of a stress-activated cation channel? | Auditory hair cell in the inner ear |
| Which of the following best accounts for the fact that an action potential travels in just one direction? | A time-dependent process called “inactivation” prevents recently stimulated Na+ channels from being stimulated again for a period of time. |
| Activation of a G-binding protein signal cascades requires: | Binding of GTP to the -subunit of the heterotrimer G-binding protein. |
| Chloroplasts: | - Have both an inner and an outer membrane like mitochondria. - Are the site of carbon fixation by plant cells. |
| Action potential becomes much more positive than the normal value. She removes all natural cytoplasm from the squid axon and replaces it with solution identical to natural cytoplasm except it contains 2XNa+ as does normal cytoplasm. Successful? | No |
| Cells generate responses to signaling through both long- and short-term effects/targets. Short term (rapid or immediate) signaling effects are generally controlled by: | - Rad generation of second messengers such as cAMP, IP3, and Ca2+. |
| Cells signal one another through four general mechanisms that differ in the mechanism whereby the signal moves from cell to cell. Which of the following types of signaling is correctly described? | - Contact dependent: direct contact of a signal bound by one cell to receptor on the other cell. |
| Two different cells respond differently to a signal produced by a nearby cell. What are possibly reasons why this might be the case: | - 1 contains receptor for the signal while other doesn't - Both contain receptor for signal but amplify differ - 1 cell is closer to the signaling cell & receives more of signal - cells respond to other signals, some outputs are integrated differently |
| Calmodulin | Is a Ca2+ binding protein and functions inside the cell to mediate the effects of increases in cytosolic Ca2+ -one of its targets is CaM kinase |
| The steroid hormone receptors depend on the _________ property of steroids as receptor ligands. | - Hydrphobic and therefore membrane permeable |
| Cells that are missing the enzyme phospholipase C (PLC) can make which of the following second messengers: | - cAMP (cyclic AMP) - cGMP (cyclic GMP) |
| Cells that are missing the enzyme phospholipase C would be expected to be deficient in processes depending on elevation of cytosolic ___________ which is released from __________ -localized stores by a PLC-dependent mechanism. | - Ca2+; ER |
| Activation of G-protein linked receptors leads to __________ of heterotrimeric G protein complexes. | - GDP to GTP exchange on alpha subunits and dissociation of them from the beta-gamma subunits. |
| G protein coupled receptors are very often ____________. | - Plasma membrane localized 7 transmembrane domain containing proteins. |
| Activation of enzyme-linked receptors such as receptor tyrosine kinases requires ____________ to cause ________________ . | - Dimer formation; phosphorylation/signaling complex formation |
| Inner membrane of mitochondria & axon membrane of nerve: both amount ions & total charge on either side of membranes are not equivalent (rapid transport across these membranes to create different outcomes). The combination of charge difference across the | - Electrochemical gradient |
| Channels vs. Carriers | - Both can exhibit high substrate specificity - Both can move solutes down their concentration or electrochemical gradients - Both are transmembrane proteins - Some channels can be normally opened by sensing of mechanical stress |
| Integrins are heterodimeric proteins involved in signaling and adhesion and are found in the plasma membrane of cells. | True |
| Membranes are not permeable to which of the following molecules on their own? | - Ions such as Na+, Ca2+, Cl-, K+ - Uncharged polar macromolecules such as glucose and dNTPs |
| The Ras protein is activated by which general type of signaling? | - Receptor tyrosine kinase/enzyme linked |
| The function of MAPK proteins is to phosphorylate and activate RTKs once they have bound their ligands. | False |
| Synaptic vesicles contain ________ that diffuse across the synapse to the target cell. The vesicles that dock with presynaptic membranes do so in response to ________ . | - Neurotransmitters; voltage gated influx of Ca2+ |
| Glucose can be transported against its concentration gradient & into cells if it is co-transported w/a Na+ that is moving down its E.G. This type of __ occurs in apical portion of gut epithelial cells & for glucose in this case it is an ex of __. | - Symport; active transport |
| Most cells maintain a membrane potential such that the intracellular side of the membrane is slightly ______. The ion Na+ has a local concentration on the extracellular side of the membrane is generally ____ than the intracellular side. | - Negative; Greater |
| The concentration difference across the membrane mentioned in question 19 is maintained by a pump, the _____, which uses the energy of ____ to cotransport ions into and out of the cell. | - Na+/K+ exchanger; ATP hydrolysis |
| Nerve cells transmit signals along axons in the form of action potentials. As an action potential passes along the axon membrane it is locally _____. | - Changed in voltage potential from negative internal to neutral and transiently positive. |
| Mitochondria | - # & morphology maintained in cells by equilibrium of fission & fusion - derived from ancient endosymbionts of early eukaryotes - Genomes contain different mitochondrial genes (circular/linear) - Function in intracellular signaling steps of apoptosis |
| Mitochondria vs. Chloroplasts | - Both have an ATP Synthase - Both use a proton (H+) gradient to energize ATP synthesis - Both have an inner and outer membrane |
| GPCRs typically can signal through all of the following: | - DAG (diacylglycerol) - cAMP (cyclic AMP) - IP3 (inositol triphosphate) - PKA (protein kinase A) |
| Activated Tor kinase operates in eukaryotic cells to: | - Promote metabolism via inhibition of protein degradation and stimulation of protein synthesis |
| Both free GTP bound G-alpha and free G-bettagamma subunits are able to signal to and regulate effector target proteins of GPCR pathways. | True |
| The G protein regulated target protein adenyl cyclase, upon activation, increases cAMP levels. This in turn activates: | - Protein Kinase A (PKA) |
| Antibodies contain two binding sites per molecule for their specific targets. If you added antibodies recognizing either GPCRs or RTKs to the cell medium, what might you expect to potentially activate signaling and why? | - RTKs because the antibodies could facilitate the dimerization of the receptors, allowing them to phosphorylate themselves and recruit signaling complex proteins. |
| Glycine acts as inhibitory neurotransmitter (gate channels in neurons changing electrochemical nature of cell membrane & thus the probability of firing action potential). What ion is being admits to cells via glycine gated channel & nature of its effect? | Glycine is gating Cl- entry into cells to increase their internal electronegative potential (i.e. increasing the magnitude of the degree of- charge inside the cell relative to outside), thereby inhibitin the initiation of action potentials. |
| Gated Na+ channel, open: transition thru inactive conformation where it can't transport Na+, b4 resetting to close state, immediately b re-open. Inactive pd reestablishes resting electrochemical potential & helps direct action potential 4ward down axon. | True. |
| In contrast to their inner membranes, the outer membranes of mitochondria contain porins that make them freely permeable to a variety of ions and solutes. | True |
Created by:
Ash T.
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