Card Set Information
Covers material for 1st test
Study of the logic of life
No longer just FUNCTION - understand how/why life works
Using purpose as a means of explanation
Ie, we breathe to oxygenate our bodies
Using cause and effect as a means of explanation
Ie, concentration gradients are created in capillary beds and drive exchange
Define the key relationship for Quantity in mathematical terms
Quantity = Concentration x Volume
Volume can be exchanged for Flow
Define the key relationship for Flow in mathematical terms
Flow = Force x Conductance
Flow = Force / Resistance
The property of an open system (organism) to regulate its internal environment to maintain a stable, constant condition
Accomplished by adjusting multiple dynamic equilibriums which are controlled by interrelated control mechanisms
Relative ion concentrations of:
Positive > Negative
Relative ion concentrations of:
Positive > Negative
Relative ion concentrations of:
Negative > Positive
K+ > Cl- > Na+
: there are many negatively charged proteins
How large is the volume of plasma?
How large is the volume of the ISF?
Name the organs used to maintain the ISF
How large is the volume of the intracellular fluid?
How is water lost?
How is water obtained?
Water content in food
How much water is typically lost in a day?
Describe the point of this experiment:
Osmolarity acts as a regulator of homeostasis
The increased amount of fluid into the system dropped osmolarity of the blood
This triggered increased renal filtration to re-establish proper levels
What constitues the plasma membrane?
A lipid bilayer (hydrophobic in, hydrophilic out)
What is the fluid mosiac model?
Describes the motility/fluidity of the membrane
Proteins and lipids are free to diffuse around
Membrane can buckle and expand
How does the PM act as a barrier?
It is semipermeable based on molecule: size, polarity, and solubility
What are the PM's functions?
Bearer of self-identity markers/transport proteins
What are the two types of membrane proteins?
What are the types of integral proteins?
Carrier - must change shape to permit passage
Channel - always open
What are the types of unassisted membrane transport?
What are the types of assisted membrane transport?
What is diffusion?
Spreading of molecules based solely on their thermal energy
Move from high => low concentration
What is the difference between Brownian motion and diffusion?
Diffusion only occurs down a concentration gradient (until uniformly dispersed)
BM describes the actual motion - when gradient is abolished, movement still occurs
Factors that affect diffusion
Lipid solubility of molecule
Membrane surface area
Molecular weight of molecule
How can membrane channels be selective?
Residues within the "ion filter" portion selectively filter the correct ion
What is the difference between diffusion and carrier-mediated transport?
Carrier-mediated requires conformational change of protein
Carrier-mediated may require energy input
Carrier-mediated reaches a saturation point (speed of which protein can change shape maxed)
What factors affect speed of carrier-mediated transport?
What are the types of active transport?
Primary - require direct use of ATP
Secondary - driven by ion concentration gradient established by a primary pump
Does facilitated diffusion require energy input?
What are the types of vesicular transport?
Which cells have a membrane potential?
How is a membrane potential established?
Differences in charge are sequestered to opposite sides of the PM
What is the resting membrane potential?
The separation of charge across the PM in all cells
Nerves maintain this when they are not firing an action potential
What controls the membrane potential?
Approximate size of things:
Pores' existance was postulated long before they were discovered (due to size)
Describe the "ionic hypothesis"
The membrane potential is determined by the intracellular K+
Used squid axon
Describe the "sodium theory"
Membrane potential in nerves is based both on intracellular K+ and extracellular Na+
Hodgkin & Huxley
Had better instruments - could see action potential better
What was incorrect about the "ionic hypothesis"?
Stated an AP was generated to due breakdown of membrane potential
Did not account for Na+
What is the Nernst equation?
Em = ~(60/z) log10 [K+]outside / [K+]inside (mV)
For 1 ion
z = charge
What does the Nernst equation describe?
At equilibrium, the force exerted by ion concentration is balanced by force exerted by charge
Chemical vs Electrical
What is the Goldman-Hodgkin-Katz Constant Field Equation?
It accounts for numerous ions permeating the PM
Can simplify to Nernst when permeability of one ion >> other
Define the relative permeabilities of ions during an AP
At rest, K >> Na
At peak AP, NA >> K
What is a patch clamp?
Allows researcher to analyze (hopefully) a single ion channel in a membrane
The abolishment of a membrane potential
The re-establishment of a membrane potential
The further reduce (more negative) the membrane potential
To increase (make less negative) the membrane potential
How to local anesthetics work?
As a weak base, they can cross membrane in uncharged state
Inside cell, the charged form can bind to voltage gated Na+ channels
Prevent generation of an AP
What are the 3 major channels used in axons?
Voltage gated Na+
Voltage gated K+
What is crenation?
The wrinkling of a cell (ie, RBC) due to a high salt solution
How can water pass across PM?
By osmosis across bilipid layer (slow)
Thru aquaporins (fast)
Describe the structure of aquaporins
6 transmembrane segments that associate into an hourglass shape
What are the two branches of aquaporins?
Orthodox - extremely selective to water
Cocktail set - homologs; will let similar molecules pass
The net diffusion of water down its concentration gradient
Thru a selectively permeable membrane impermeable to the SOLUTE
Moves from low => high SOLUTE CONCENTRATION
When does osmosis reach equalibrium?
When osmotic pressure = hydrostatic pressure
Measure of a solution's total solute concentration
Expressed in Osmoles/L
A colligative property
What is a colligative property?
One that depends solely on the number of particles, not the nature of them
What is the normal osmolarity of body fluids?
What is the van't Hoff limiting law?
π = RTΦic
Calculates osmotic pressure
"i" is the number of moeities the molecule dissolves into
"c" (molarity) can also be substituted for "m" (molality)
Φ is the osmotic coefficient
Closer to ideal the more dilute a solution is
What is the osmotic coefficient (Φ) for some solutions?
Ideal = 1
Monovalent = 0.9-0.95
Multivalent < 0.9
Mono-/disaccharides ~ 1 (a little over)
Determining net flow of water
(net) = K
σ is the reflection coefficient
is the filtration coefficient
What is the reflection coefficient (σ)?
σ = 1 - P(solute)/P(water)
Describes the permeability of the solute
σ = 1, impermeable
σ = 0, permeable
What factors affect K
Related to the size of the membrane
Related to relative conductivity of water thru the membrane
Why do body cells not normally experience volume changes?
The concentration of nonpenetrating solutes in the ECF is carefully regulated to match the osmolarity of the ISF
The effect nonpenetrating solutes in a solution have on cell volume
Describe the difference between tonicity and osmolarity
Osmolarity has units to describe concentration in each compartment
Tonicity is merely the relative concentration between two compartments
Equal solute concentrations between compartments
[Solutes in ECF] > [Solutes in cell]
[Solutes in ECF] < [Solutes in cell]
What is the isotonic condition for RBCs?
Can proteins penetrate capillaries?
What is the mechanistic reason for molecule exchange in capillary beds?
Net blood pressure entering causes solutes to cross into tissues
Net osmotic pressure exiting causes the reverse
What makes the capillary beds ideal for exchange?
Maximized surface area
Velocity of blood flow is relatively slow
How to pass a capillary
Water soluble molecules can diffuse thru water-filled gaps
Lipid soluble can diffuse across endothelial PM
Proteins CANNOT diffuse across
What drives the osmotic pressure in capillaries?
Since all other solutes have a σ~0, and proteins are σ~1, only the proteins affect osmotic pressure
What is the Starling equation?
Describes how net pressure on either end of the capillary beds drives molecule transport