Term
| What type of molecules and ions are able to transverse the lipid bilayer? |
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Definition
| Small, uncharged, polar molecules and gases can diffuse without help (i.e. CO2, N2, O2, ethanol) |
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Term
| Which type of molecules and ions require help to transverse the lipid bilayer? |
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Definition
| Large, uncharged polar molecules, ions, and charged polar molecules are impermeable and require transport |
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Term
| Which types of molecules can cross the membrane by simple diffusion |
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Definition
| Gases and small uncharged molecules |
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Term
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Definition
| relative diffusion rate of any substance if proportional to its concentration gradient across th bilayer, the greater the concentration gradient of the substance the rater its rate of movement across the bilayer |
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Term
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Definition
| determined by measuring its partition coefficient K, the equilibrium constant for partition between oil and water. Higher K = more lipid soluble and faster it will diffuse across the bilayer. |
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Term
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Definition
| the electric potential (voltage) across the membrane, influences substances movement across the membrane if that substance has a net charge |
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Term
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Definition
| combination of concentration gradient and membrane potential, determines the energetically favorable direction of movement of a charged molecule across a membrane |
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Term
| For which types of substances does the electrochemical gradient affect transport? |
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Definition
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Term
| three main classes of membrane proteins... |
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Definition
| ATP-powered pumps, Channels and Transporters |
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Term
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Definition
| utilize the energy released by ATP hydrolysis to power movement of specific ions or small molecules against their electrochemical gradient |
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Term
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Definition
| channels permit movement of specific ions (or water ) down their electrochemical gradient |
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Term
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Definition
| facilitate movement of specific small molecules or ions |
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Term
| What are the membrane transport protines similarities? |
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Definition
| They are all Transmembrane proteins containing multiple membrane spanning segments that generally are alpha helices |
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Term
| What are the membrane transport protines difference? |
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Definition
| Transport different substance, either with or against their concentration gradient |
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Term
| Which types of transport proteins transport against the concentration or electrochemical gradient? |
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Definition
| ATP powered pumps and transporters (only antiporters and symporters) |
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Term
| Which types of transport proteins transport down the concentration gradient? |
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Definition
| Channels and transporters (only uniporters) |
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Term
| What is the difference between active transport and facilitated transport? |
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Definition
| Active transport requires ATP |
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Term
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Definition
| transport is against the concentration gradient, and the transport is coupled to ATP hydrolysis, transports ions, small hydrophilic molecules, and lipids |
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Term
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Definition
| transports glucose and amino acids via uniporters and ions and water via channels. This type of transport does not require ATP and the solutes are being transported with their concentration gradient. |
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Term
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Definition
| A protein gate blocks the channel or moves out of the way to open the channel in response to specific chemical or electrical signals. |
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Term
| How is transport through a channel different from a pump? |
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Definition
| Pumps move via active transport against the concentration gradient and need ATP |
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Term
| How are uniporters different from symporters and antiporters? |
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Definition
| Uniporters move with the concentration gradient |
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Term
| Three types of transporters |
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Definition
| Uniporters, symporters, and antiporters |
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Term
| If it is a gas, or a small uncharged polar molecule |
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Definition
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Term
| If it is a large, uncharged polar molecule like glucose or fructose |
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Definition
| it will use facilitated transport via uniporters |
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Term
| If it is an ion, like K+, Mg2+, Ca2+, Cl-, HCO3-, or HPO42 |
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Definition
| and moving with its concentration gradient it will use facilitated transport via channels, if it is moving against its concentration gradient it will move via active transport via ATP-powered pumps |
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Term
| If it is a charged, polar molecule, like amino acids, ATP, Glucose-6-phosphate, proteins or nucleic acids |
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Definition
| it will move via facilitated transport via uniporters with its concentration gradient or by cotransport via symporters and antiporters. |
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Term
| List 5 features that distinguish uniport transport from simple diffusion |
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Definition
1. Uniporters move substrate faster than simple diffusion
2. K is irrelevant
3. Vmax is dependent upon the number of uniporters in the membrane. Vmax is achieved when the concentration gradient across the membrane is very large and each uniporters is working at its maximal rate
4. Transport is reversible and dependent on the direction of the concentration gradient
5. Transport is specific, each uniporter has a specific molecule which it transports |
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Term
| Describe how Km influences the directionality of transport for the GLUT1 uniporter |
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Definition
| GLUT1 has a low Km and this enables it to transport glucose into most mammalian cells |
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Term
| Describe experimental approaches used to study membrane transporters using recombinant proteins |
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Definition
| gene encoding a specific transport protein can be expressed at high levels in a cell type that normally does not express it |
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Term
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Definition
| generates a pressure because of water flow to equalize solute content, it is the hydrostatic pressure that would have to be applied to one solution to prevent the natural water flow that equalizes the solute concentration |
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Term
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Definition
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Term
| What is the function of an aquaporin? |
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Definition
| They quickly transport water to maintain ionic gradients across the membrane and increase the permeability of biomembranes to water |
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Term
| How many classes of aquaporins are found in humans? |
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Definition
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Term
| Discuss the relationship between mutations in the vasopressin receptor and aquaporin 2 genes and the disease diabetes insipidus. |
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Definition
| Aquaporin 2 in the plasma membrane of certain kidney cells is essential for resoprtion of water from urine being formed; the absence of aquaporins 2 leads to the diabetes insipidus because large amounts of urine are excreted. |
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Term
| List the four main classes of ATP powered pumps |
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Definition
| P-class, F-class, V-class, and ABC transporters |
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Term
| Compare and contrast the ligands transported by P, F and V pumps as compared to ABC transporters |
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Definition
| P, F and V class pumps move ions, ABC transporters move bigger molecules |
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Term
| What does the acronym ABC transporter stand for? |
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Definition
|
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Term
| Structure of P class pumps |
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Definition
| have two catalytic alpha subunits which becomes phosphorylated, the beta subunit regulated transport |
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Term
| Structure of V and F class Pumps |
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Definition
| pumps do not becomes phosphorylated, structures are similar and contain similar proteins |
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Term
| Sttructure of ABC transporters |
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Definition
| contain two Transmembrane (T) domains and two cytosolic ATP-binding (A) domains |
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Term
| Function of P-class pumps |
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Definition
| are seen in plasma membranes and sarcoplasmic membranes, they pump H+, Na+/K+, and Ca2+ |
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Term
| Function of F-class pumps |
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Definition
| are seen in plasma membranes, inner mitochondrial membranes, and thylakoid membranes, they function as a reverse proton pumps and move protons from the exoplasmic to cytosolic face down the proton electrochemical gradient which provides energy to make ATP |
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Term
| Function of V-class Pumps |
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Definition
| are seen in some plasma membranes and vacuolar and endosomal membranes, they generate low pH by pumping protons from cytosolic to exoplasmic face of a membrane against a proton gradient |
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Term
| Function of ABS transporters |
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Definition
| seen in plasma membranes, they pump specific substrates or groups of substrates. |
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Term
| Do ATP pumps transport with or against the concentration gradient? |
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Definition
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Term
| Describe the general mechanism of the Ca2+ ATPase in muscle. |
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Definition
1. ATP binds to a site on the cytosolic surface and is hydrolyzed to ADP
2. Protein undergoes a conformational change
3. Ca2+ ions dissociate and enter lumen
4. Phosphate bond is hydrolyzed
5. Conformational change
6. Now the protein can transport two more Ca2+ into the lumen |
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Term
| What is the Ca2+ ATPase function? |
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Definition
|
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Term
| What protein regulates the Ca2+ATPases function? |
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Definition
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Term
| Which class does the Ca2+ATPase pump belong to? |
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Definition
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Term
| Describe the mechanism of action of drugs such as ouabain and digoxin with regard to the Na+K+ ATPase. |
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Definition
| These drugs bind to the exoplasmic domain of the plasma membrane Na+K+ ATPase and specifically inhibit its ATPase activity |
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Term
| Describe the major function of V-class ATPases in the cell. |
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Definition
| Maintain the acidity of lysosomes and vacuoles |
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Term
| Describe the general functions of ABC transporters |
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Definition
|
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Term
| Examples of ABC transporters |
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Definition
| ABCB1- exports lipophilic drugs, ABCB4- exports phosphatidylcholine into bile |
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Term
| Discuss the role of ABC transporters in human disease using Cystic Fibrosis as an example. |
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Definition
| CFTR is a Cl- channel protein, not an ion pump. Channel opening is triggered by protein phosphorylation and by binding of ATP to the two A domains, a mutation causes the protein to fail to fold properly and move into the cell surface where it normally functions, this causes CF |
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Term
| Describe how patch clamp techniques can be used to study non-gated channels. |
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Definition
| Permit the measurement of ion movements through single channels are used to determine the ion conductivity of a channel and the effect of variations signals on its activity |
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Term
| Compare and contrast gated versus non-gated channels |
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Definition
| Gated channels open in response to various signals and Non-gated channels are always open (K+ channels) |
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Term
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Definition
| transported molecule and cotransported ion move in the same direction |
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Term
|
Definition
| transported molecule and cotransported ion move in the opposite direction |
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Term
| Describe how symporters can be used to pump against a concentration gradient. |
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Definition
| use the energy released by movement of an ion down its electrochemical gradient to power the import or export of a small molecule of different ion against its concentration gradient |
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Term
| Describe how drugs such as oubain used in congestive heart failure target Na+/Ca2+ antiporter. |
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Definition
| o These drugs lower the cytosolic K+ concentration and simultaneously increased cytosolic Na+. The resulting reduced Na+ electrochemical gradient across the membrane causes the Na+ linked Ca2+ antiporter to function less efficiently. These drugs increase the force of the heart muscle contractions. |
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Term
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Definition
| separate the apical and basolateral membranes and prevent many water soluble substances on one side from moving across to the other side through the extracellular space between cells |
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Term
| Classes of membrane transport proteins include all of the following except |
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Definition
|
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Term
| How does uniport transport compare to simple diffusion? |
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Definition
| Uniport transport is much faster and more specific than simple diffusion |
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Term
|
Definition
|
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Term
| When computing the osmotic pressure that must be placed across the membrane to stop the flow of water, what is the glucose osmotic equivalent of 1 M CaCl2? |
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Definition
|
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Term
| Which of the four classes of ATP-powered pumps share overall similarity: several subunits, the same general organization, and a similar function in being H+ transporters? |
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Definition
| F-class pumps and V-class pumps |
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Term
| The major ATP-powered pump responsible for maintaining ion gradients across the plasma membrane of mammalian cells is |
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Definition
| the plasma-membrane Na+/K+ ATPase |
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Term
| ABC superfamily proteins are thought to act as ATP-dependent transporters some of which function in transporting |
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Definition
| lipophilic drugs out of mammalian cells. |
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Term
| Which statement describes the mode of action of the ABCB1 transporter (the first eukaryotic ABC transporter to be recognized)? |
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Definition
| During transport, the ligand binding site is alternately exposed to the exoplasmic and the cytoplasmic side of the membrane |
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Term
| Which of the following statement(s) is (are) true of V-class proton pumps? |
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Definition
| They are ATPases, They are present in membranes of plant vacuoles, and they serve to decrease the pH inside a lysosome |
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Term
| The resting membrane potential in animal cells depends largely on nongated ____ channels |
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Definition
|
|
Term
| The magnitude of the membrane electrical potential is calculated by |
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Definition
|
|
Term
| How does inhibition of the Na+/K+ ATPase increase the force of heart muscle contraction? |
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Definition
| It increases cytosolic Na+ and therefore decreases Ca2+ export |
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Term
| Transepithelial glucose transport uses a symport to transport glucose up a concentration gradient by |
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Definition
| coupling glucose transport to Na+ movement. |
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Term
| Parietal cells acidify the stomach contents while maintaining a neural cytosolic pH by |
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Definition
| exporting excess cytosolic OH- as HCO3-, exchanging HCO3- for Cl- and preserving electroneutrality by accompanying the movement of each Cl- into the stomach lumen by a K+ |
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Term
| Transepithelial transport requires a cell layer |
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Definition
| that is polarized and sealed |
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Term
| Which of the following would be expect to diffuse across the cell membrane most easily? |
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Definition
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