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28 Cards in this Set
- Front
- Back
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What kinds of molecules CAN go through a membrane w/out a transporter?
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Hydrophobic (drugs, carcinogens; small uncharged polar (water, urea, glycerol)
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What kinds of molecules canNOT go through a membrane w/out a transporter?
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Large uncharged polar molecules (like sugars and nucleosides); charged molecules like amino acids and nucleotides
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What is membrane transport?
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The movement of molecules across cell membranes.
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What are the two classes of membrane transport?
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Protein-mediated; simple membrane diffusion
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What are the characteristics of simple diffusion:
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Nonspecific and very slow (relatively); use for h-phobic and nonpolar
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What are the two main classes of membrane transport proteins?
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Transporters and channels
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How do transporters work? What are they?
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They are pumps that pump molecules against the electrochemical gradient. They are enzymes.
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What's a passive transporter?
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An enzyme that accelerates the rate @ which a molecule achieves equilibrium across the cell membrane, providing an alternative rxn pathway.
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What's an active transporter?
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SOME use ATP to create rapid solute movement against a concentration gradient (upill). OTHERS use Na+ and K+ gradients to drive a molecule against its chem gradient.
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What's the major difference between passive and active transport?
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Passive: substrate diffuses down chemical gradient; nondirectional. Active: substrate goes up its chemical gradient using energy; directional
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What are the three types of passive transporters?
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Uniport, symporter, and antiport.
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Describe a uniport transporter.
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Passes only 1 molecule. Simple carrier. Goes from high [s] to low [s].
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Describe an antiport transporter.
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Exchange only carrier. Exchanges one molecule for another. If you had high [Na+] in and high [Ca2+] out, you need both to bind, undergo conformational change, and then exchange one for the other.
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What are the characteristics of simple diffusion:
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Nonspecific and very slow (relatively); use for h-phobic and nonpolar
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What are the two main classes of membrane transport proteins?
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Transporters and channels
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How do transporters work? What are they?
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They are pumps that pump molecules against the electrochemical gradient. They are enzymes.
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What's a passive transporter? What's a classic example?
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An enzyme that accelerates the rate @ which a molecule achieves equilibrium across the cell membrane, providing an alternative rxn pathway. Example: the GluT1 Glucose transporter (must have D-glucose).
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What's an active transporter?
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SOME use ATP to create rapid solute movement against a concentration gradient (upill). OTHERS use Na+ and K+ gradients to drive a molecule against its chem gradient.
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How does a passive transporter work?
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The transporter is in open confirmation. It binds. It closes and let the molecule fall into the cell. Its either open OR closed. Never both @ the same time.
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What are the 3 kinds of active transporters?
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Symport. Uniport. Antiport.
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Describe symport.
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Co-transprot. Use Na/K gradients to drive a substrate against its chemical gradient. Everything goes in one direction. One is driving force, and other drags ion against its chem gradient. Examples are neurotransmitter transport in synaptic cleft and sugar and a.a. transport in epithlia.
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Describe uniport, ATPase.
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Use ATP from inside cells to pump stuff outside.
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Antiport (ATPase).
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1/3 of ATP is burned by this pump. Na outside and K inside for every ATP hydrolysis
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Na+/K+ ATPase. Some details.
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1/3 of a cells ATP is used for this pump. Goes 100times/sec. We transfer 3Na+ outside and 2K+ inside (against gradient); closely coupled to ATP hydrolysis. It sets the gradient in all our cells.
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What are the two kinds of channel proteins and how are they different?
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more coming
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Name the three kinds of gated channel proteins.
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more coming
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Define the term used to describe transportation of solutes in a transporter protein and describe describe how it works.
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Alternating Confirmation Model. Confirmation change is independent of solute binding and net direction of transport determined by solute concentration (gradients).
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What is a classic example of a passive uniporter?
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GLUT1 in RBCs
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