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100 Cards in this Set
- Front
- Back
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What are the 2 Common Charateristics to All biological Membranes
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Same Basic strurcture
are selectively permeable |
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What 2 ways can a substance pass through a membrane
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Transport Protien
simple diffusion |
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What charateristics must a substance posses to pass through the lipid biylayer
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small size
soluble in lipd |
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What is simple diffusion
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the passive transport of substances along their concentration graidents toward equilibrum
It is a single step reaction follows flicks law V=P(ChgC) always exergonic- energy is released |
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what is the permiablity constant in flicks law?
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P= Permiablity constant it is the rate constant of simple diffusion which is determined by the solubility and size of the molecule
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Relations between solubility permeiablity constant and veloicity
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as solubility increases, permiabliity increases and velocity increases
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relations between size permiablity and velocity
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as size increases permeablity decreases and velocity decrease
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Substances that use simple diffusion
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Small Hydrophobi molecules
o2, n2, benzene Small uncharges polar molecule h20, glycerol, ethanol |
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what is osmosis?
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Osmosis is the movement of water across a semipermeable membrane from a compartment of low osmotic pressure to a compartment of high osmotic pressure.
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What does semipermiable mean?
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As the term is used here, a semipermeable membrane is a membrane that is permeable to water but NOT permeable to a select group of solutes.
• These solutes that are NOT permeable through the membrane are called osmotically active solutes.” |
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what is osmotic pressure?
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Osmotic pressure is a pressure exerted by these
osmotically active solutes Osmotic pressure is directly proportional to the concentration of these “osmotically active” solutes. |
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What is the permeability pathway taken by water
during osmosis? |
The water permeability pathway of many membranes
consists solely of the lipid bilayer. Some cells and some organelles require a much faster rate of osmosis The water permeability pathway of the membranes of these cells & organelles consists of the lipid bilayer & transport proteins that transport water. The special transport proteins are called “aquaporins”. |
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What are Aquaporins?
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Special transport protiens that are only for transporting water in the membrane
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what do aquaporins consist of?
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4 identical subunits
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Aquaporins and Water Reabsorption in Kidney
Epithelial Cells |
Epithelial cells lining the “collecting ducts of the kidney
– Note: • Structure: tight junctions form apical and basolateral domains of the cells. • Water transport is forced through the cells, not between the cells • Water transport is regulated by a hormone: Antidiuretic hormone (ADH) through a cascade that involves cAMP and Protein Kinase A The final result of this cascade is to insert aquaporins in the apical membrane. |
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what are transport protiens?
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membrane protiens that transport substances accross the membrane
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what are the 2 basic charateristics of all the transport protiens?
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all are transmembrane proteins
all are highly selective for the substrate |
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how do you classify transport protiens?
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Passive and Active
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What consists of a passive transport protien?
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transport down a gradient
no external source of energy needed |
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what does an active transport protien consist of ?
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transport up a gradient
requrires external energy input |
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what are the charateristics of carrier protiens?
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contain a substrate binding site on a hydorphilic domain of the protien
opperates according to the alternating conformation mechanism |
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what is the alternating conformation mechanism?
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when the carrier protien opperates between 2 conformations
1- the binding site has a high substrate binding affinity when it is exposed to one side 2- the binding site has a low substrate binding affinity when it is exposed to other side change in confromation is induced by the binding or release of a substrate |
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How do carrier protiens behave like enzymes?
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both utilize substrate binding sites
exhibits similar michelis menten lke saturation kinetics |
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what are the 2 categories of carrier protiens
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uniports- 1 substrate in 1 direction
contransport- 2 substrates, (1 in 2 opp directions, other in same) |
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what are the subcategories of the contransport
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symport- 2 directions= same
antiport-2 directions = opp |
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Facilitaive diffusion vs Simple difusion
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Facilitated diffusion uses a transport protien and simple does not
Both passive and move down concentration gradient |
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Glucose accross plasma membrane + Transport protiens
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all animal cells need glucose because it is the primary source for the production of ATP and needs a transport protien
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Why is glucose transported into cells via a transport protein?
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glucose is not permiable through the lipid bilayer
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Why is facilitated diffuson used in the movement of glucose?
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there is a high concentration of glucose outside the cell
there is a low inside the cell glucose is needed and is a large polar molecule |
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what is the carrier protien of glucose?
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GluT1, transmembrane protien that is multipass ( 12 membrane spannins segments), a uniport carrier, single glucose binding site
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How does the facilitated diffusion of glucose happen?
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through 2 conformations
1- glucose binding site has a high binding affinity when exposed to the outside of the cell where the concentration of glucose is high 2-the glucose binding site has a low substrate binding affingity when exposed to the inside of the cell where the concentration of glucose is low |
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what is the importance of gradients?
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cells must maintain the gradients for purposes of energy conservation through active transport
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what is active transport?
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transports substances against the concentration gradients inorder to maintain the concentration and requires an imput of chemical energy
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Where does the energy come from to move accose a concentration gradient?
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Through ATP hydrolosis, breaking of phosphate bonds releases usable energy
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What is Direct Active transport+ ATP hydrolosis?
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The energy from ATP hydrolysis is applied directly to the transport mechanism
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what is indirect active transport + ATP hydrolosis?
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energy from ATP hydroplosis is applied indirectly to the transport mechanism
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How are direct active transpot mechanisms carried out?
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by ATPases - are proteins that hydrolyze ATP and apply the energy to an acitve transport mechanism
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What are the types of ATPases?
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P-Type
V-Type F-Type ABC-Type |
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What does the P type ATPase consist of?
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always activly tranfers cations
self phosphoralates during hydrolosis |
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What is the V-type ATPase?
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ATP is hydrolozied but transport protien is not phosphoralated
Pumps H+ into vesicles such as lysosomes Not a selfphosphoralationg protein |
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What is the F-type ATPase?
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AKA ATP synthases
Found in the Mitochondria cholorplasts, bacteria H+ transport Not a self phosphoralating Protien |
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What are the Major P type ATPases?
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Uniport: Ca+ ATPases
IN The ER & Plasma Membrane Antiport: NA+, K+ ATPase Found in Plasma Membrane of Animal Cells and H+, K+ ATPase found in the parietal cells of the the stomach |
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What does the Ca2+ ATPase Do?
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pumps ca2+ ions out of the cytosol
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What is the basic structure of the Ca2+ ATPase?
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Single protein (10 pass)
• 2 large cytosolic loops – Between M2 and M3 – Between M4 and M5 • All functionality on this single proetin – Cation binding – ATP binding – ATPase activity – Phosphorylat |
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What does the folded protein of the Ca2+ ATPase consist of?
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– Membrane domain
• Made of the 10 membrane spanning segments • Contains binding sites for 2 Ca++ ions – Cytoplasmic (cytosolic domain • Made of the 2 large cytosolic loops • 3 functions – ATP binding – ATP hydrolysis (ATPase activity) – Site of phosphorylation |
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How many conformations does ATPase have?
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2
E1-, E2 change in conformation is induced by the binding or release of Ca2+ ions, inorganic phosphate from ATP hydrolosis |
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What Happens in the E1 conformation of a Ca2+ ATPase?
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In the E1 conformation (open to cytosol)
1. 2Ca++ bind tightly to the Membrane domain (high Ca++ binding affinity)from the cytosolic side 2. ATP binds to the cytosolic domain 3. ATP hydrolysis and Phosphorylation of the cytosolic domain (ca++ dependent phosphorylation) 4. Conformational change to the E2 conformation |
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What happens during the E2 Conformation of the Ca2+ ATPase?
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In the E2 conformation (open to noncytosolic side)
1. Ca++ released from the Membrane domain (low Ca++ binding affinity) to the noncytolic side of the membrane 2. Dephosphorylation of the cytoslic domain 3. Conformational change back to the E1 conformation |
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What are the Important features of the conformations in the Ca2+ ATPase?
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Important features
– ATP hydrolysis and Phosphorylation are Ca++ dependent – Ca++ binding and phosphorylation are required for conformational change from E1 to E2 – Dephosphorylation is promoted by Ca++ release – Ca++ release and Pi required for conformational change from E2 to E1 |
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What is the purpose of te Na/k+ ATPase?
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To maintain the resting Na+ and K+ electrochemical Gradients
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What is the structure of the Na+/K+ ATPase?
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4 subunit, 2 Beta (glycoprotiens) 2 Alpha (Each is a 10 pass protien for Na+ binding – K+ binding – ATP binding – ATPase activity
– Phosphorylated |
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What is the E1 Conformation of the Na+/K+ ATPase?
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Na+ sites have a high binding affinity when open to the cytosolic side, while the K+ have a low binding affinity
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What is the E2 Conformation of the Na+/K+ sites?
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WHen open to the EC side
Na+ has a low binding affinty K+ sites have a high binding affinity |
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When does a change in conformation occur in an Na+/K+?
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With the binding or relesase of Na+ and K+ aswell as inorganic phosphates
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What is the diagram for the Na+/K+ ATPase mechanism?
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3 sodiums are taken from inside, ATP phosphoylates alpha subunits, causes a confromational change following phosphoralation expels 3 Na+ to the outside,
2 K+ are accepted from outside,Dephosphoralation triggers confroamtion change, 2 K+ are expelled to inside pump returns to initial state |
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what is the average voltage accoss a plasma membrane
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85mv
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what does the distribution of ions accoss a plasma membrane create?
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a separation of charge across the membrane
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what are the volatages of NA K CL in the Extra cellular Fliid and overall charge?
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Na= 145
K=5 Cl=125 Over all charge is positive |
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What are the voltages of Na K and Cl in the intra cellular fluid and overall voltage?
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Na-10
K-140 cl-10 Overall voltage = Negative |
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what can the goldman equation be used for?
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To calculate the resting membrane potiential shown by combining the permiablity coeffiecents and concentration gradients of three major ions Na, K, Cl
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What is the action potential?
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a specific rapid fluctuation in the membrane potential of an excitable cell
it has two phases... Depoloarizatoin and Repolarization |
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what is the depolarization phase of action potential?
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it is due to a rapid influx of Na+ ions
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what is the repolarization phase of action potential due to?
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a rapid efflux of K+ ions
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What are the properties of Channel Protiens?
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Aqueous channel
2. Transport mechanism does not employ a substrate binding site . . . 3. . . . nor does it operate via the alternating conformation mechanism. 4. Mechanism of transport: simple diffusion 5. Three Major Families: |
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what are the 3 major families of channel protiens?
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1.Voltage-Gated Ion Channels
2. Ligand-Gated Ion Channels 3. Major Intrinsic Protein |
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what are voltage gated ion channels?
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Molecular gates are regulated by changes in membrane potential or voltage
Typically closed at resting state, opens when membrane potential drops quickly |
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what are the 3 major types of voltae gated ion channels
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Na+
K+ Ca2+ |
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what is the specific role of voltage gated ion channels?
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generation and conduction of an action potential
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what is teh strutural organization of voltage regulated gate
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Some gates have one
component: an activation gate Some gates have two components: an activation gate and an inactivation gate. |
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what is the sturture of the voltage gated Na+ channels?
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Monomeric, 4 domains, each domain 6 pass
Extracellular loops within domains Intracellular loops between domains |
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what ate the features of the Na+ Voltage gated Ion channel?
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The Voltage Sensor: S4.
(High concentration of + charged amino acids) • Selectivity Filter: extracellular P loops (loop between S5 and S6) - determines selectivity of pore • The Activation Gate: Localization NOT settled. Likely S6. • The Inactivation Gate: Cytosolic Loop between Domain III S6 and Domain IV S1 |
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How does the Voltage gated Na+ channels opperate?
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It has 3 conformations
closed resting inactive |
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What does the open conformation consist of?
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the activation gate open
the inactivation open resulting in the Na+ diffuse down their EC gradeint (influx) causing depolaization |
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what does the inactive conformaiton consist of?
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activation gate open
inactive gate closed resultins in the stop of Na+ influx, ending depolarization adn membrane is refractory |
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what does the closed conromation consist of?
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activation gate closed
inactivation gate open results in a no longer refractroy |
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what does the structure of the voltage gated K+ Channel consist of ?
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Multimeric, 4 subunits, each subunit 6 pass – identical to Na+ channel domains
Extracellular loops within subunnits No intracellular loops between subunits |
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What are the features fo the voltage gated K+ channels?
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The Voltage Sensor: S4.
High concentration of + charged amino acids • Selectivity Filter: P loop (loop between S5 and S6) - determines selectivity of pore • The Activation Gate: Localization NOT settled. Possibly S6. • NO INACTIVATION GATE |
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waht are teh 2 basic conformations of the voltage gated K+ channels?
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closed
open resting= closed, activation gate closed |
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What does the open conformation of the voltage gated K+ channels consist of?
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activation gate opened
resulting in the K+ diffuse down their EC gradient causing repolarization of the membrane |
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what is the state of voltage gated K+ channels during the action potential?
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1 (at rest)
– K+ closed conformation • 2 (depolarization) – K+ still closed conformation • 2a (end of depolarization) – K+ open conformation • 3 (repolarization) – K+ still open conformation |
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What is the role of Ion Channels in synaptic transmission?
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Ca2+ ion channels are found in the presynaptic membrane
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What is the operation of a chemical synapse?
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Depolarization of presynaptic
membrane • NT vesicles fuse with the presynaptic membrane • NT released and diffuses across synaptic cleft • NT binds to receptors on the postsynaptic membrane • Depolarizes the second cell • Depolarization of presynaptic membrane • NT vesicles fuse with the presynaptic membrane • NT released and diffuses across |
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what is the role of the Ca2+ channels in the presynaptic membrane?
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Depolarization of
presynaptic membrane 2. Voltage-gated Ca++ channels briefly open. 3. Brief influx of Ca++ along its EC gradient - Results in an increase in the local concentration of Ca++ within the terminal bulb. 4. Ca++ stimulates the fusion of vesicles with presynaptic membrane. 5. Neurotransmitter is released into the synaptic cleft… |
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What is the structure of the Ca2+ voltage gated channel in the presyanaptic membrane?
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Monomeric, 4 domains, each domain 6 pass
Extracellular loops within domains Intracellular loops between domains |
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what type of channels are found in the postsynaptic membrane?
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Ligand-regulated ion channels
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what are ligand-gated ion channels?
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also known as neurotransmitter receptors
They belong to a channel protein family: Ligandgated Ion Channel (LIC) Family • Binding of a ligand (neurotransmitter) to the channel protein opens the gate |
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what are the 5 basic classes of LICs?
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Acetylcholine receptors
• Serotonin receptors • Glycine receptors • Glutamate receptors • Gamma-aminobutyric acid (GABA) receptors |
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what is the basic structure of a ligand-gated Ion channel?
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Pentameric channel
• Each subunit is a 4- pass protein |
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what is the structure of the acetylcholine receptor?
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• 5 subunits
– 2 alpha • @ 1 acetylcholine binding site – 1 beta – 1 delta – 1 gamma • Each subunit is a 4- pass protein – M1, M2, M3, M4 • The 5 M2 α helices line the pore and form the gate. |
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How does the Acetylcholine receptors work?
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Bulky hydrophobic leu chains of M2 helices close the channel
with the binding of 2 acetylcholine molecules causing twisting of the M2 helicies with the receptor sites occupoed the M2 helicies have smaller polar residues lining the channel and open |
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What is the role of the Ligand-gated ion channels?
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Neurotransmitters acetylcholine binds to teh receptor protein causing it to open and allowing Na+ to diffuse down the EC gradient
resulting in the depolarization of the postsynaptic membrane |
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where do endergonic reaction get their needed energy?
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From specific coupled exergonic reactions with specific carrier molecules (ATP)
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what does the structure of ATP consist of?
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Three Pi (inorganic phosphates, alpha beta gamma)
Ribose (pentose sugar) Adenine (nitrogenous base) |
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what holds the inorganic phosphates together in the ATP structure?
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Phosphoanhydride bonds
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What does hydrolosis have to do with ATP?
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when ATP's phosphate bonds are hydrlozied (ATP- ADP)causes a release of energy that can be used to cople with reactions
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Which Hydrolosis reaction is primarly used for chemical energy?
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the hydrolosis of the terminal phosphanhydride bond on ATP
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where does the cell get the energy to create ATP?
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Oxidation of high-energy coenzymes usually NAD+
as the cell reduces NAD+ into NADH it gives off energy that is coupled to take ADP and a Phosphate to create ATP |
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where do you get energy to reduce NAD+ and produce NADH
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from the oxidation of inorganic fuels such as glucose and fatty acids
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what is a metabolic pathway?
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a series of enzymecatalyzed
reactions in which the product of one reaction is the substrate for the next. |
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what is the example of a metabolic pathway?
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Glucose- glycolosis (oxidation of glucose)-oxidative decarboylation of pyruvate(produciton of large quantites of NADH + H+)- citic acid cycle (same as above)- Mitochondrial Electron Transport Chain- Production of Large quantities of ATP
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