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Phys Exam 1: Ch 4
Membrane Transport & Basics of Signal Transduction
| Question | Answer |
|---|---|
| Describe 3 methods for membrane transport by simple diffusion. Give an example of an ion or solute that is transported by each mechanism. | 1.Diffusion of lipid-soluble molecules; O2, CO2, Ethanol. 2.Diffusion thru pores (non-gated channels); Aquaporins - H2O. 3.Diffusion thru ion channels (voltage- and ligand-gated); Na+, K+ |
| Name 5 factors that affect the rate of diffusion of an ion or solute through a pore or channel. | 1.Concentration gradient, 2.# of pores in the membrane/# of OPEN ion channels, 3.Selectivity filter of the pore or channel, 4.Electrical Potential difference, 5.Pressure (capillary hydrostatic pressure) |
| If a drug is chemically modified to be more hydrophobic, would the rate of diffusion across a lipid bilayer increase, decrease, or stay the same? | Increase |
| If aquaporins are removed from the lipid bilayer, would the rate of diffusion of water across a lipid bilayer increase, decrease, or stay the same? | Decrease |
| After the opening of voltage-gated K+ channels, would the rate of diffusion of Na+ across a lipid bilayer increase, decrease, or stay the same? | Increase |
| Compare & contrast primary (1*) vs. secondary (2*) active transport. The activity of which pump is the primary driving force for secondary active transport for most cells? | 1*:energy needed to transport ion or molecule AGAINST favorable gradient via exergonic chemical rxn (ATP hydrolysis), use pumps; 2*:Downhill transport of 1 ion/molecule coupled w/uphill transport of another ion/molecule; exchangers or cotransporters |
| True or False: The Na+/K+ pump transports 3K+ to the extracellular fluid and 2Na+ into the intracellular fluid. | FALSE: 3Na+ --> extracellular, 2K+ --> intracellular |
| True or False: The Na+/K+ pump is electroneutral. | FALSE: electrogenic (moving an unequal amount of charge); 1.Creates negative charge inside cell to maintain negative resting membrane potential; 2.Establishes electrochemical gradients for movement of Na+ & K+; 3.Helps maintain cell volume |
| True or False: The Na+/K+ pump uses the energy liberated from the ATP hydrolysis to drive the transport of ions across a lipid bilayer. | TRUE: the liberated energy drives conformational changes in the pump. |
| True or False: The Na+/K+ pump acts as an ATPase enzyme. | TRUE: the pump cleaves a high-energy phosphate bond of 1 ATP molecule |
| True or False: The Na+/K+ pump helps to maintain cell volume by pumping more ions out of the cell than in. | TRUE: By pumping more ions out of the cell (3 Na+) than in (2 K+), the pump helps balance osmolarity and movement of H20. Ex: If cell volume increases, pump activity increases |
| True or False: Ca2+ concentration in the cytoplasm is higher than the extracellular fluid for most cells. | FALSE: Cytoplasmic [Ca2+] is kept EXTREMELY LOW |
| True or False: There are no 1* active transport mechanisms for Ca2+. | FALSE: Primary active transport for Ca2+ into internal stores (sarco/ER, vesicles) and out of the cell. |
| True or False: The 2* active transport of Ca2+ is driven primarily by the activity of the Na+/K+ pump. | TRUE: The transport of Na+ out of the cell by the Na/K pump encourages 2* transport of Na into the cell and Ca out of the cell via the Na/Ca exchanger |
| True or False: Epithelial membrane transport can only occur by simple diffusion across tight junctions. | FALSE: simple diffusion, facilitated diffusion, Primary Active Transport, Secondary Active Transport |
| True or False: In epithelial membrane transport, the apical and basolateral membranes express identical carrier proteins. | FALSE |
| True or False: For membrane transport across epithelia, secondary active transport is driven primarily by the activity of the Na+/K+ pump. | TRUE: Na/K pump on the basolateral side sets up the [gradient] for Na to come in thru the apical side, which draws in glucose with it |
| Compare & contrast endocrine vs. paracrine vs. autocrine cell signal | Endocrine: signal travels thru bloodstream Paracrine: b/n 2 adjacent cells (ex: neuronal synapse) Autocrine: cell makes & secretes signaling molecule (ex: immune system activation) |
| Name 5 common signal transduction pathways. | Receptor Tyrosine Kinases, Ligand-gated Ion Channels, Steroid Hormone Receptors, Antigen Binding Receptors, G-protein Coupled Receptors |
| For Receptor Tyrosine Kinases, identify an example of a specific receptor, the signaling molecule the receptor binds, and the general outcome of the signal. | Receptor = ?; signaling molecule = growth factors; Outcome = cell growth, differentiation |
| For Ligand-gated Ion Channels, identify an example of a specific receptor, the signaling molecule the receptor binds, and the general outcome of the signal. | Receptor = Nicotinic ACh receptors; signaling molecule = neurotransmitters; Outcome = neurotransmission |
| For Steroid Hormone Receptors, identify an example of a specific receptor, the signaling molecule the receptor binds, and the general outcome of the signal. | Receptor = ?; signaling molecule = steroid hormones; Outcome = multiple (sex hormones, etc) |
| For Antigen Binding Receptors, identify an example of a specific receptor, the signaling molecule the receptor binds, and the general outcome of the signal. | Receptor = ?; signaling molecule = pathogens; Outcome = immune response |
| For G-protein Coupled Receptors, identify an example of a specific receptor, the signaling molecule the receptor binds, and the general outcome of the signal. | Receptor = ?; signaling molecule = multiple; Outcome = multiple |
| Describe the general mechanism for activation of a G-protein. | 1.extracellular signalling molecule binds to G-protein complex; 2.alpha-subunit releases and binds to receptor protein; 3.(a)DAG releases and binds to enzyme, (b)IP3 releases, causes Ca2+ release from ER |
| Describe the general mechanism for activation of a Receptor Tyrosine Kinase. Why are these molecules, or molecules in these signaling pathways frequently mutated in human cancers? | 1.extracellular signalling molecule binds; 2.ATP is hydrolyzed 3.tyrosine is phosphorylated (phosphorylated dimer) and is activated; 4.Activated protein system causes the cellular resoponse |
| Why are the molecules, or molecules, in Receptor Tyrosine Kinase signaling pathways frequently mutated in human cancers? | Because they play key roles in cell growth, proliferation, and differentiation |
| Discuss the clinical correlation of Multi-Drug Resistant Transporter 1 (MDR1) for Primary Active Transport | 1.ATP-binding cassette (ABC) protein; 2.Use the energy of ATP hydrolysis to expel cationic metabolites and hydrophobic drugs across the cell membrane; 3.Defense mechanism in cancer cells turn on MDR1 and renders them resistant to chemotherapeutics |
| Which ions are higher on the outside of the cell? | Na+, Ca2+,Cl-, HCO3-, Glucose |
| Which ions are higher on the inside of the cell? | K+, Mg2+, Phosphates |
Created by:
hclark86
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