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30 Cards in this Set
- Front
- Back
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The 2 main types of transport are:
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Nonmediated Transport
Mediated Transport |
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What is the difference between active and passive transport in terms of energy use?
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- Passive transport (PT) does not require an input of energy.
- PT goes down a concentration gradient. - PT is driven by a difference in concentrations - Active transport (AT) requires an input of energy. - AT is often against a concentration gradient |
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ΔG_A for non-charged particles:
If [A]_out > [A]_in, what type of reaction is this? What does this say about the net flow rate of molecules? |
If [A]_out > [A]_in, then you'll have -ΔG_A, which correlates with a spontaneous process.
This means that there will be a net flow of molecules *into* the cell, from the outside |
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What are 6 reasons that we need membrane transport?
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1) Import biological molecules (fuel and building blocks)
2) Export of waste 3) Transport of building blocks or degradation products between organelles and the cytoplasm 4) Regulate osmotic pressure 5) Regulate concentration of cetrain ions 6) Create gradients of ions across membranes. |
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What 2 things affect the equilibrium of concentration gradients?
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1) Ionic charge
2) Difference in electrical potential |
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Through what process does non-mediated transport occur?
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Simple diffusion
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What types of molecules undergo non-mediated transport?
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Non-polar molecules
EXAs: O₂ and steroids |
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What 2 things affect the rate at which substances diffuse across membranes?
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- Substances diffuse in the direction that eliminates their concentration gradient, at a rate proportional to the magnitude of the gradient.
- The rate of diffusion of a substance also depends on its solubility in the membrane's nonpolar core. |
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What types of molecules undergo mediated transport?
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Polar or charged molecules.
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What is required before a molecule can pass across a membrane using mediated transport?
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A specific carrier protein
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What are the 2 categories of Mediated Transport?
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1) Passive-mediated Transport
2) Active transport |
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What is another name for "Passive-mediated Transport"?
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Facilitated diffusion
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Describe the process (briefly) of Passive-mediated Transport
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Molecules flow from high concentration to low concentration.
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Describe the process (briefly) of Active Transport
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A specific molecule is transported from *low to high* concentration (i.e. against it's concentration gradient.
Requires energy in the form of ATP |
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Define and state the function of:
Ionophores |
Ionophores are organic molecules that increase the permeability of a membrane to ions.
Ionophores carry ions across membranes. |
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The 2 types of Ionophores are:
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1) Carrier Ionophores
2) Channel-forming Ionophores |
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Describe the function of:
1) Carrier Ionophores 2) Channel-forming Ionophores |
1) Carrier Ionophores
increase the permeability of membranes to their selected ion by binding it, diffusing through the membrane, and releasing the ion on the other side. 2) Channel-forming Ionophores Form transmembrane channels or pores through which their selected ions can diffuse. |
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What type of Ionophore is Valinomycin an example of?
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Valinomycin is a Carrier Ionophore
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What ion does Valinomycin transport across a membrane?
What types of bonds hold Valinomycin together? |
K+
Peptide bonds and Ester bonds |
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True/False:
Valinomycin transports K+ across a membrane, but it can also transport other cations such as Na+ and Li+. |
False.
Valinomycin is very *specific* for K+. Valinomycin has an affinity for K+ 10,000 times greater than that for Na+. |
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Describe the structure of:
Gramicidin A Gramicidin A's pore |
GENERAL STRUCTURE:
- A linear polypeptide containing D and L amino acids (15 residues) - Momomers form a helix that spans half the membrane - Side channels are mostly h-phobic. PORE: - Unusual helix: 6.3 residues per turn - N-H and C=O groups alternate pointing up and down - Central core is 4 angstroms in diameter - Conducts {H+, K+, Na+, Li+} |
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Valinomycin and Gramicidin A are similar in that they are both _____.
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...antibiotics!
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How do Valinomycin and Gramicidin A kill cells?
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They equalize their ion gradients that exist across the plasma membrane.
* This disrupts the necessary gradients that exist within cells, upsetting their equilibrium. |
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What type of super-secondary structure are porins?
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β-Barrels
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What are 6 characteristics of:
Ion Channels |
- Usually specific
- Found in all cells - Maintain osmotic balance - Signaling - Conductance of action potentials - Most ion channels are gated |
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What are 3 things that regulate Ion Channels?
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Hormones
Membrane potentials touch (mechanosensitive) |
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What are 4 types of Gated Channels?
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1) Mechanosensitive channels
2) Ligand gated channels (outside) 3) Signal gated channels (inside) 4) Voltage gated channels |
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What are 5 characteristics of:
Transport Proteins |
1) Fixed in the membrane
2) Do not form a channel (selective) 3) Alternate between two configurations - ensures only specific molecules are transported 4) Binding site is open at only one side of the membrane at a time 5) Conformational switch leads to binding site opening on other side of membrane |
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What are the 3 types of Transport Proteins?
How do they differ? |
Uniport = Transport in 1 direction
Symport = Transport 2 things in the same direction Antiport = Transport 2 things in *opposite* directions |
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Briefly describe the transport of glucose through an erythrocyte membrane.
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[10.13] pg. 307
1) Glucose bind to the protein on one face of the membrane 2) A conformational change closes the first binding site and exposes the binding site on the other side of the membrane (transport) 3) Glucose dissociates from the protein. 4) The transport cycle is completed by the reversion of GLUT1 to its initial conformation in the absence of bound glucose (recovery) |
