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59 Cards in this Set
- Front
- Back
What is a Transporter?
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It is class of membrane transport proteins that has moving parts to shift small molecules from one side of the membrane to the other.
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What is a Channel?
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It is a class of membrane transport proteins that form tiny hydrophilic pores in the membrane that solutes can pass by diffusion.
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What are the 5 most plentiful ions of all the solutes in a cell's environment?
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1. Na+
2. K+ 3. Ca2+ 4. Cl- 5. H+ |
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Is Na+ most plentiful inside or outside the cell? What about K+?
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Na+ is the most plentiful OUTSIDE the cell whereas K+ is the most plentiful INSIDE the cell
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If they're small enough, what 2 things can readily diffuse across the lipid bilayer? Give examples for both.
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1. Small nonpolar molecules (O2, CO2)
2. Uncharged polar molecules (water, ethanol) |
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Lipid bilayers are highly impermeable to what?
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All ions and charged molecules, no matter how small.
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Membrane Transport Proteins fall into what 2 classes?
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1. Transporters
2. Channels |
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Channels discriminate passage of molecules based on what two things?
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1. Size
2. Charge |
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Transporters allow passage only to what?
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Molecules or ions that fit into a binding site on the protein!
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What is Passive Transport?
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Also called Facilitated Diffusion is diffusion down the concentration gradient (high to low) without using any energy
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What is Active Transport?
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Movement of a molecule across a membrane (usually from low to high concentrations) driven by ATP hydrolysis or another form of metabolic energy.
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The lysosome membrane contains what kind of transporter that acidifies the interior?
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H+ transporters!
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The inner membrane of mitochondria contains what kind of transporters so it can generate ATP and export it?
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Pyruvate transporters which is used for fuel for ATP generation
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What does Glucagon do?
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It stimulates the liver cells to produce large amounts of glucose by the breakdown of glycogen!
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How is the binding sites for glucose transport highly selective?
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The transporter will only bind D-glucose for transfer NOT L-glucose which cannot be used for glycolysis.
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What is Membrane Potential?
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Difference in the electrical potential on each side of the membrane
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Does the cytoplasmic side of the plasma membrane usually have positive or negative potential relative to the outside?
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Cytoplasmic side usually has a NEGATIVE potential (thus pulls positively charged solutes into the cell and negatively charged ones out of the cell.)
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What is Electrochemical Gradient?
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Gradient caused by both concentration gradients and voltage potential gradients across the membrane!
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What are the 3 main ways cells carry out active transport?
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1. Coupled transporters
2. ATP-driven pumps 3. Light-driven pumps |
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What are coupled transporters?
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Active transporters that couple the uphill transport of one solute across the membrane to the downhill transport of another.
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What are ATP-Driven Pumps?
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Active transporter that couple uphill transport to the hydrolysis of ATP
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What are Light-Driven pumps?
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Active transporter mostly found in bacteria that couples uphill transport to the input of energy from light
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Animal cells use what to pump out Na+?
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The energy of ATP hydrolysis!
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The Na+ - K+ pump is also called what?
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Na-K ATPase
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The Na-K pump is not only a transporter. What is it also?
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An enzyme called an ATPase because it hydrolyzes ATP to ADP to transport Na+ out of the cell and K+ into the cell.
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What happens if ouabain is introduced to a cell?
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It halts the operation of the Na-K pump but the energy in this store is sufficient to sustain the cell for many minutes.
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What is the net driving force for movement of K+ across the membrane?
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Close to zero: electric force pulling K? into the cell is almost exactly balanced by the concentration gradient tending to drive it out.
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The Na-K pump is driven by the transient addition of what?
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The transient addition of a phosphate group!
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What are the 6 stages in the Na-K pump cycle?
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1. Na+ binds to pump
2. Pump phosphorylates itself 3. Phosphorylation triggers conformational change and Na+ is ejected into ECF 4. K+ binds 5. Pump is dephosphorylated 6. Pump returns to original conformation and K+ is ejected into ICF |
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The net result of one cycle of the Na-K pump is the transport of how many Na+ and K+ ions?
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3 Na+ ions out of the cell and 2 K+ ions into the cell!
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What is Osmosis?
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The movement of water from low to high SOLUTE concentrations. (In other words, the movement of water from high to low WATER concentrations.)
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The driving force for the movement of water is what?
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The difference in water pressure called the Osmotic Pressure.
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In the absence of any counteracting pressure, the osmotic movement of water will cause a cell to do what?
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Swell
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What is Turgor Pressure?
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The pressure exerted by water inside the cell against the cell wall.
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Is Ca2+ kept in high or low concentrations in the cytosol?
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LOW concentrations!
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The downhill movement of the first solute down its gradient provides what?
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The energy to drive the uphill transport of the second solute!
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If the transporter moves both solutes in the same direction across the membrane, what is it called?
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Symport
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If the transporter moves moves two solutes in opposite directions, what is it called?
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Antiport!
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A transporter that ferries only one type of solute across the membrane is called what? Is it still a coupled transporter?
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Uniport! It is no longer considered a coupled transporter.
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What is a type of H+ pump in bacteria?
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Bacteriorhodopsin
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In animals, what is the purpose of an H+ pump found in some lysosomes?
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To pump H+ out of the cytosol to keep the pH of the cytosol neutral and the pH of the interior of the organelle acidic.
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Ion channels have what 2 important properties?
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1. Ion-selective
2. Gated |
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Regarding ion channels, ion selectivity depends on what 3 things?
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1. diameter of channel
2. shape of channel 3. distribution of the charged amino acids that line the channel |
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What is Patch-Clamp Recording?
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Technique in which the tip of a glass electrode is sealed into a patch of cell membrane, thereby making it possible to record the low of current through individual ion channels in the patch.
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Why is Patch-Clamp Recording important (think clamp)?
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Its ability to expose the membrane to different specific voltages makes it possible to see how changes in membrane potential affect the opening/closing of the channels.
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What is a Voltage-Gated Channel?
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Membrane protein that selectively allows ions to cross a membrane and is opened by changes in membrane potential.
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What is a Ligand-Gated Channel?
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An ion channel that opens when it binds a small molecule such as a neurotransmitter.
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What is a Stress-Gated Channel?
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Membrane protein that allows the selective entry of specific ions into a cell and is opened by mechanical force.
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What type of channel does the ear use to transmit sound signals to the brain?
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Stress-gated channels!
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Voltage-gated channels have specialized charged protein domains called what? What are they?
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Voltage sensors that are extremely sensitive to changes in the membrane potential.
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What are Leak Channels?
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Channels that randomly flicker between open and closed states no matter what the conditions are inside or outside the cell.
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What is the Resting Membrane Potential?
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Membrane potential in steady-state conditions (flow of positive and negative ions across membrane is precisely balanced)
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What is the Nernst Equation?
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Equation that expresses the equilibrium quantitatively and makes it possible to calculate the theoretical resting membrane potential if internal to external [ion] in known.
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What is the actual Nernst Equation assuming 37 C temperature?
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V = 62log(outside concentration/inside concentration)
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What is Curare?
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Drug that blocks the delivery of excitatory signals at neuromuscular junctions thus causing paralysis.
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What are the 2 common excitatory neurotransmitters?
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1. Acetylcholine
2. Glutamate |
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What are the 2 main inhibitory neurotransmitters?
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1. GABA
2. Glycine |
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Excitatory neurotransmitters activate ion channels that allow what ions passage?
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Na+ and Ca2+
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Inhibitory neurotransmitters activate ion channels that allow what ion passage?
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Cl-
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