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35 Cards in this Set
- Front
- Back
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why is Facilitated diffusion considered passive transport?
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Because the solute is moving down its concentration gradient.
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Does facilitated diffusion speed or slow down the transport of a solute?
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speed up. It provides an efficient passage through the membrane.
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Can facilitated diffusion alter the direction of transport?
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no.
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Can transport protein move solutes against their concentration gradients?
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yes, they can move solutes across the plasma membrane from the side where they are less concentrated to the side where they are more concentrated.
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What is active transport?
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When a transport protein moves solutes against a concentration gradient.
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Are transport protein that move solutes against a concentration gradient channel protein or carrier protein?
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carrier protein
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True or False: Active transport enables a cell to maintain internal concentraions of small solutes that differ from concentrations in its environment.
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True. For example, compared with its surroundings, an animal cell has a much higher concentration of potassium ions and a much lower concentration of sodium ions.
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What supplies the energy required for active transport?
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ATP
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One way ATP can power active transport is by transferring its terminal _________ group directly to the transfer protein.
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phosphate
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How does a phosphate group being given to a transport protein help in transporting?
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It makes the protein change its shape in a way that translocates a solute bound to the protein across the membrane.
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How does a sodium-potassium pump exchange sodium for potassium across the plasma membrane of animal cells?
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by a protein gaining a phosphate group and being translocated across the membrane.
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True or False: Some cells don't have voltages across their plasma membrane.
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False. All cells have voltages across their plasma membranes. (a separation of opposite charges.) p. 136
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Is the cytoplasm positive or negative in charge relative to the extracellular fluid?
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negative
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Why does the cytoplasm have the charge that it does?
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because of an unequal distribution of anions and cations on opposite sides of the membrane.
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What is membrane potential?
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The voltage across the membrane.
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________ ________ is the voltage across the membrane.
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membrane potential
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the membrane potential ranges tom ____ to _______ millivolts.
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-50 to -200
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_______ _______ acts like a battery.
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membrane potential
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How does the cytoplasm being negative affect the traffic of the cell?
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It favors passive transport of cations into the cell and anions out of the cell
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What are the two forces that drive the diffusion of ions across a membrane?
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chemical force (concentration gradient) and eletrical force (the membrane potential.)
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When we talk about chemical force in relation to diffusion, what are we specifically talking about?
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the concentration gradient
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What is electrochemical gradient?
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the combination of electrical force and chemical force for diffusion
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An ion diffuses not simply down its concentration gradient, but down its ______________ gradient.
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electrochemical
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True or False: In cases where electrical forces due to the membrane potential oppose the simple diffusion of an ion down its concentration gradient, nothing can be done.
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False. Active transport may be necessary and can intervene. p. 137
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True or False: All membrane proteins contribute to the membrane potential.
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False. Only proteins that are actively transport ions contribute to membrane potential. (p.137)
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A transport protein that generates voltage across a membrane is called an ________ _______
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electrogenic pump
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What is an electrogenic pump?
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A transport protein that generates voltage across a membrane.
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What is an example of an electrogenic pump?
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sodium-potassium pump
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What is phosphorylation?
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the addition of a phosphate group to a substance.
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What is the major electrogenic pump of animal cells?
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sodium-potassium pump
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What is the main pump of plant, fungi, and bacteria?
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proton pump
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What does a proton pump do?
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it actively transports hydrogen ions (protons) our of the cell.
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One important use of proton gradients in the cell is for _________ synthesis.
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ATP
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What happens in cotransport?
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When a single ATP-powered pump transports a specific solute can indirectly drive the active transport of several other solutes.
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True or False: A substance that has been pumped across a membrane can do work as it moves back across the membrane by diffusion.
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True. Similar to water that has been pumped uphill, it can perform work as it flows back down. p.137
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