# Shared Flashcard Set

## Details

Fundamentals I Test 3 McNicholas
Flash Cards for Dental School
73
Biochemistry
Professional
09/12/2010

Term
 What is the Nernst Equation?  And what do the variables represent?
Definition
 E = 60/z * log(Co/Ci) E = Nernst Equilibrium Potential z = charge of ion Co = [outside] Ci = [inside]
Term
 What are the conditions for Active Transport under the Nernst Equation?
Definition
 The actual intracellular concentration differs from the calculated concentration.
Term
 What are the conditions for Passive Transport under the Nernst Equation?
Definition
 The actual internal concentration is the same as the calculated concentration.
Term
 How does a pressure gradient effect water flow?
Definition
 Fluid flows from an area of high pressure to low pressure.
Term
 What does the initial rate of water flow after a pressure change depend on?
Definition
 Magnitude of pressure difference Area of membrane (P = F/A) Hydraulic Conductivity (Permeablility) of membrane
Term
 How does the movement of water respond to differnces in osmotic pressure?
Definition
 Water flows from low to high osmotic pressure
Term
 How does the movement of water respond to differences in water concentration?
Definition
 Water flows from high water concentration to low water concentration
Term
 How many osmolytes ae in one molecule of Sucrose? NaCl? MgCl2?
Definition
 1 osmolyte 2 osmolytes 3 osmolytes
Term
 What amount of NaCl would be needed to balance 100mM of sucrose?
Definition
 50 mM NaCl
Term
 What amount of sucrose would be needed to balance 100mM of MgCl2?
Definition
 300mM
Term
 What are the three major fluid compartments in the body?
Definition
 Blood Plasma, Interstitial Fluid, & Intracellular Fluid
Term
 Rank the four fluid compartments from largest to smallest according to volume.
Definition
 Intracellular Fluid (25L), Interstitial Fluid (13L), Blood Plasma (3L), and Transcellular Fluid (1L)
Term
 What are the three major ions in the fluid compartments?  Where is each ions concentration the highest?
Definition
 Na+: 142mM BP, 145mM Inter, 15mM Intra K+: 4.4mM BP, 4.5mM Inter, 120mM Intra Cl-: 102mM BP, 116mM Inter, 20mM Intra
Term
 How does osmolarity differ among the four major fluid compartments?
Definition
 It is at a constant 290mOsm in all compartments
Term
 Rank the fluid compartments from highest protein concentration to lowest.
Definition
 Intracellular Fluid (4mM), Blood Plasma (1mM), and Interstitial Fluid (0mM)
Term
 What molecules are freely permeable across the membrane?
Definition
 Gas & Small uncharged molecules
Term
 What is the function of the Extracellular Matrix?
Definition
Term
 What are the proteins in the Extracellular Matrix and what are they responsible for?
Definition
 Collagen, fibronectin, laminin, and elastin Functions: structural or adhesive
Term
 What are the polysaccharides in the Extracellular Matrix and what are they responsible for?
Definition
 Glycosaminoglycans: covalently bound to protein backbone
Term
 How do cells attach to the ECM?
Definition
 via transmembrane glycoproteins called integrins
Term
 What is the role of the Cytoskeleton?
Definition
 supports & stiffens cell, provides anchorage for proteins, contributes to dynamic whole cell activities (dividing & crawling)
Term
 What are the three cytoskeletal fibers?
Definition
 Microtubules, Microfilaments, & Intermediate filaments
Term
 What cell type are tight junctions found? And what is their purpose there?
Definition
 epithelial cells - maintain polarity of epithelial cells
Term
 T/F Adhering Junctions are only found in epithelial cells.
Definition
 F - They're found in epithelial & non-epithelial cells
Term
 What is the major role of Gap Junctions?
Definition
 allow passage of solutes from cell to cell, cell-cell communication, & propagation of electrical signal
Term
 What portion of the cell involves carbohydrates covalently attached to membrane proteins & lipids and forms a slimy surface coating.
Definition
 Glycocalyx
Term
 What portion of the cell is responsible for sorting embryonic cells into tissures & organs and rejecting foreign cells by the immune system?
Definition
 Glycocalyx
Term
 What is Fick's first law of diffusion in words and equation?
Definition
 "The rate of flow of an uncharged solute due to diffusion is directly proportional to the rate of change of concentration with distance in direction of flow"   Flux = Js = DsΔCs/Δx
Term
 When must the net flux equal zero?
Definition
 When the concentration gradient of a substance is zero.  Also means that the system is at equilibrium.
Term
 What is the partition coefficient and what variable is represented by it?
Definition
 Ks; increases or decreases driving force of solute (S) across membrane
Term
 What variables are included in the Permeability Coefficient?  What variable represents the Permeability Coefficient?
Definition
 Ks, Ds, & Δx Ps = Permeability Coefficient
Term
 What influences the Permeability Coefficient?
Definition
 differences in lipid solubility - Not molecular size of uncharged solute
Term
 What is the Diffusion Coefficient dependant on and what variable represents it?  How does its value relate to the radius of the solute?
Definition
 Depends on the size of the solute molecule & viscosity of the medium; Ds Ds is inversely proportional to the radius of the solute
Term
 What is Flux (Js) directly proportional to?
Definition
 A solute's lipid solubility
Term
 What is defined as the pressure required to stop the flow of water?  What variable represents it?
Definition
 Osmotic pressure; Δπ
Term
 What is the van't Hoff Equation?
Definition
 Δπ = RTΔCs = (25.4)ΔCs
Term
 The equation for the effective osmotic pressure for nonideal membranes includes what variable?
Definition
 the Reflection Coefficient = σs which has values from 0 to 1
Term
 What is the role of Oncotic Pressure in blood flow?
Definition
 Oncotic (Hydrostatic) Pressure does not change as blood passes through a capillary bed because proteins are not allowed to move across the membrane.  This pressure draws water back into the capillaries as it leaves the capillary bed.
Term
 Define an Isotonic Solution. How does water move in this scenario?
Definition
 The osmolarity inside the cell is equal to that outside the cell; water has no net movement
Term
 Define a Hypertonic Solution. How does water move in this scenario?
Definition
 Higher concentration outside the cell than inside; water leaves the cell
Term
 Define a Hypotonic solution.  How does water move in this scenario?
Definition
 Higher concentration inisde the cell that outside; water moves into the cell
Term
 What is the Principle of Bulk Electroneutrality?
Definition
 Number of positive charges in a solution must equal the number of negative charges.  All solutions must obey this principle.
Term
 What two forces govern the movement of electrolytes?
Definition
 Chemical & Electrical
Term
 Describe a Diffusion Potential
Definition
 The ion with the smaller radius will move slightly ahead of the larger ion which causes a diffusing dipole.  A series of these leads to a diffusion potential.  The leading charge will characterize one side of the membrane; the lagging charge will characterize the other.
Term
 What are the typical equilibrium potentials for Na+, Cl-, K+, and Ca2+?
Definition
 ENa = +67 ECl = -89 EK = -95 ECa = +123
Term
 What does the Goldman-Hodgkin-Katz (GHK) Equation calculate?
Definition
 It allows you to compute the voltage across a membrane permeable to more than one ion.  It takes into consideration the permeability of all ions.
Term
 How would an increase in membrane permeability to Na+ effect the resting membrane potential?
Definition
 Sodium would enter the cell which makes the resting membrane potential more negative/less positive.
Term
 How would an increase in Cl- permeability effect the resting membrane potential?
Definition
 Cl- would rush into the cell causing the membrane potential to be more postive/less negative.
Term
 How would an increase in K+ permeability effect the resting membrane potential?
Definition
 K+ would rush out of the cell causing the membrane potential to be more positive/less negative.
Term
 What is the source of energy and the molecular pathway for diffusion?
Definition
 No energy is needed, molecules are driven by their concentration gradient; molecules move straight through phospholipid bilayer.
Term
 What is the source of energy and the molecular pathway for facilitated diffusion?
Definition
 No energy is needed, molecules are driven by their concentration gradient; molecules move through a protein channel or pore
Term
 What is the source of energy & the molecular pathway for Secondary Active Transport?
Definition
 Energy provided by primary active transport, molecules go against concentration gradient; uses a channel or pump
Term
 What is the source of energy and the molecular pathway for Primary Active Transport?
Definition
 Energy comes from ATP, molecules go against concentration gradient; molecules move through a channel or pump
Term
 Describe the mechanism used by the Na-K ATPase pump.
Definition
 Primary Active Transport: Cytoplasmic Na binds, ATP phosphorylates, Na released to outside, extracellular K binds, phosphate group released, K released inside cell
Term
 What is the mechanism for Ca to move across the membrane?
Definition
 Released down concentration gradient via gated channels, pumped back in via active transport
Term
 By what mechanism do H+ ions cross the membrane?
Definition
 If anyone knows please tell me!
Term
 How does the Na gradient drive active transport of other molecules?
Definition
 Energy releasedby sodium going down its concentration gradient is used to drive the uphill movement of other solutes via Secondary Active Transport
Term
 What determines the extent to which the channel is open or closed?
Definition
 Gating
Term
 What states that Proteins can influence the distribution of other ions so that electrochemical equilibrium is maintained?
Definition
 Gibbs-Donnan Membrane Equilibrium
Term
 How does the Gibbs-Donnan Equilibrium maintain cell volume?
Definition
 The proteins within the cell are too large to exit.  This exerts osmotic pressure and retains water in the cell
Term
 How many and in which direction are Na+ & K+ pumped?  In which direction do they leak and which one leaks more?  How does this effect the resting membrane potential?
Definition
 2K+ are pumped in for every 3Na+ pumped out Na+ leaks in and K+ leaks out; K+ leaks out much faster Causing the RMP to be negative
Term
 What is found at the Apical surface of Epithelia?
Definition
 brush border (microvilli) which increases surface area; also called mucosal or lumenal
Term
 What are the other names for the basolateral membrane of epithelial cells & what is its function?
Definition
 serosal or peritubular; vectorial transport
Term
 How do tight junctions contribute to epithelial polarity?
Definition
 Form a barrier that maintains a different environment on the apical side of the cell than on the basal side
Term
 Describe Paracellular movement.
Definition
 Water and ions move across the tight junctions instead of moving across the whole cell
Term
 What term describes a steady state condition with no flow of electrical current across the membrane?
Definition
 Resting Membrane Potential
Term
 Is the Vm at rest positive or negative?  Are the conductances of Na+ & K+ high or low?
Definition
 Negative; Na+ is very low & K+ is high (conductance = permeability)
Term
 What opens voltage-gated channels?
Definition
 A stimulus that raises the intracellular potential to a threshold level
Term
 During depolarization, what is the membrane most permeable to?
Definition
 Huge increase in Na+ conductance which allows Na+ in; Still permeable to K+ and Cl-
Term
 Describe the permeablility of the membrane durring Hyperpolarization.
Definition
 Na+ channels close once potential reaches max positive point, K+ channels open letting K+ out so potential becomes more negative, K+ channels are slow to close which causes the potential to briefly be more negative than the resting potential
Term
 During which period of time is the cell incapable of eliciting a normal action potential no matter how great the stimulus?
Definition
 Absolute Refractory Period
Term
 What period overlaps with the after-hyperpolarization period & can be stimulated by a greater than normal stimulus?
Definition
 Relative Refractory Period
Term
 Durring which period is the Na+ channel inactivation gate closed?
Definition
 Absolute Refractory Period
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