Fluids & Osmosis Flashcards
1
Q
Homeostasis definition
A
maintenance of steady state in the internal environment despite changes in the external environment
2
Q
List properties of the cell membrane.
A
- selectively permeable
-
lipid soluble substances dissolve in hydrophobic lipid bilayer & therefore CAN cross cell membere
- O2, CO2, steroid hormones
-
water soluble substances cannot dissolve in lipid bilayer
- some can cross cell membrane through water filled channels or pores, or may be transported by carrier proteins
- Na+, Cl-, Glucose, H2O
- some can cross cell membrane through water filled channels or pores, or may be transported by carrier proteins
3
Q
Describe the Fluid Mosaic Model of the cell membrane
A
4
Q
Describe simple diffusion
A
- form of passive transport
- Movement of a substance along its concentration (downhill); requires no energy
- Continues until the concentration becomes equal on both sides (reaches equilibrium)
-
Rate of diffusion depends on:
- Concentration gradient
- Permeability of the membrane
- Surface area
- i.e. substances that are lipid soluble
- blood gases, steroids
5
Q
Describe facilitated diffusion
A
- transport of a substance along its concentration gradient
- facilitated by a carrier protein in the cell membrane
- passive transport (no energy)
- rate of diffusion is faster due to presence of carrier protein
- rate of diffusion reaches saturation at higher concentrations
- follows all features of a carrier mediated transport
- saturation, specificity, competition
6
Q
List 3 common features of carrier mediated transport. Which forms of membrane tranpsort involve carrier mediated tranport?
A
-
chemical specificity/stereospecificity
- glucose transporter in proximal renal tubule is specific for D-glucose, not L-glucose
-
competition sites
- can turn transporters on/off
- saturation
-
carrer - mediated transport involved in:
- facilitated diffusion
- primary active transport
- secondary active transport
7
Q
Define transport maximum (Tm)
A
- defined as the maximum rate at which a substance can be reabsorbed
- represented by the plateu phase on a graph
- at high solute concentrations, rate of transport reaches a plateau, as all the binding sites are saturated (occupied)
- at low solute concentrations, mamy binding sites are available & rate of transort increases rapidly with increasing concentrations
8
Q
Describe primary active transport
A
- transport of solutes against the concentration gradient
- low concentration → high concentration
- requires energy (ATP)
- used directly to pump solutes
- carrier protein has ATPase activity
- Examples
- Na - K pump
- digialis (turns pump off)
- Ca Pump
- H-K Pump (Proton pump)
- prilosec
- Na - K pump
9
Q
Distinguish between uniport, symport, and antiport as they related to carrier mediated transports.
A
-
uniport
- transport of a single substance
-
symport
- transport of mroe than one substance in the same direction (also called cotransport)
-
antiport
- transport of more than one substance in opposite directions (also called countertransport or exchange)
10
Q
Describe secondary active transport.
A
- solute is coupled with sodium transport and is transported against its gradient
- Na moves down its gradient but provides energy for moving the solutes uphill
- energy is used indirectly; not directly by the carrier
- driving force for the carrier is the Na concentration gradient (created by primary active transport0
- no sodium gradient → transport stop
- inhibiting Na K pump stops this transport
11
Q
Define osmosis
A
- Osmosis is NOT the diffusion of water
- Osmosis occurs because of a pressure difference
- Diffusion occurs because of a concentration difference
- water concentration of a solution is determined by the concentration of solute.
- water goes where the solute is more concentrated
- Concentration difference of solutes creates an osmotic pressure that makes water to move
- Water continues to move until the concentration of solutes become equal on both sides
12
Q
Example of osmoles
A
13
Q
Define osmotic pressure
A
- external pressure that would be required to prevent solvent flow across a membrane
- higher solute concentrations with higher osmotic pressures “draw” water
- less permeable solutes exert more effective osmotic pressure
- Na exerts greater osmostic pressure than urea which exerts no osmotic pressure
- urea is a rapidly permeating solute across the cell membrane
- Na exerts greater osmostic pressure than urea which exerts no osmotic pressure
14
Q
Define tonicity
A
- effective osmolarity of a solution
- measure of a solutions ability to create an osmotic pressure gradient relative to another solution
- “what will the solution do when it gets inside the body?”
15
Q
Distinguish between permeant solutions and impermeant solutes.
A
-
impermeant solutes
- i.e. sucrose
- remain in ECF
- cell volume won’t change → isotonic
-
peremant solutes
- i.e. urea
- move through the membrane → increasing ICF osmolality
- causes water to enter the cell, making the cell swell
- **hypotonic** (even though osmolality is the same as sucrose)
*
19
Q
Cation/Anion breakdown in ECF and ICF
A
20
Q
The volume of a compartment is determined by the _______.
A
osmoles
22
Q
What is the equation to find the volume of a compartment? Which indicators can be used to find the volume of each compartment?
A
- Plasma - Evans blue
- ECF - Inulin
- TBW - Tritiated Water
- ICF = TBW - ECF
- ISF = ECF - Plasma
23
Q
Primary solute constituents of body fluid compartments
*Diagram*
A
