Chapter 5 - Membranes Flashcards
Exam I
Explain how the body can be in osmotic equilibrium but electrical and chemical disequilibrium.
- Osmotic equilibrium does not mean that there are equal levels of molecules
- Electrical and chemical disequilibrium can mean that the levels of ions are disproportionate between ECF and ICF but in their own ‘equilibrium’
Describe the distribution of body water among compartments.
ICF - fluid is 2/3 of total body water volume
ECF - 1/3 of the total body water volume
How much water is in a “textbook normal” person.
42 L
What percentage of the ECF is plasma?
25%
what percentage of ECF is interstitial fluid?
75%
what is the only difference between interstitial fluid and plasma?
plasma has more proteins
Compare and contrast molarity, osmolarity, and osmotic pressure.
- molarity: moles solute/liter of solution
- osmolarity: osmoles/liter of solution
- osmotic pressure: minimum pressure that must be applied to prevent flow of solvent across membrane (osmosis)
Compare bulk flow to solute movement across membranes.
- bulk flow: fluid movement in response to pressure gradients
- solute movement across membranes: solute movement in response to energy requirements of transport
Explain the differences between diffusion in an open system and diffusion across biological membranes.
diffusion in an open system:
- does not require an outside energy source
- diffuse from high to low concentration
- diffusion continues until equilibrium
diffusion across membranes:
- requires energy
- rate of diffusion depends on the SA
- permeability depends on lipid composition
What is Fick’s law of diffusion?
Diffusion of an uncharged solute across a membrane is proportional to the concentration gradient of the solute, the membrane surface area, and the membrane permeability to the solute.
(rate of diffusion) is proportional to (SA) x (concentration gradient) x (membrane permeability)
What is the equation for membrane permeability?
lipid solubility / molecular size
What subcategories fall under passive protein-mediated transport across membranes?
- facilitated diffusion
- ion channel
- aquaporin channel
What subcategories fall under active protein-mediated transport across membranes?
- direct/primary transport
- indirect/secondary transport (concentration gradient created by ATP)
What subcategories fall under vesicular transport across membranes?
- exocytosis
- endocytosis
- phagocytosis
Compare movement through channels to movement on facilitated diffusion and active transport carriers.
channels:
- move ions (and water)
- passive transport
- transport down concentration gradients
- no energy input
- facilitated diffusion uses carrier molecules (GLUT transporters)
- always open to both ICF + ECF at the same time
active transport carriers:
- move different types of molecules
- change conformation
- transport against concentration gradients
-requires energy
- never open to both ICF + ECF at the same time
Apply the principles of specificity, competition, and saturation to carrier-mediated transport.
specificity: molecule has to fit the “mold” of the transporter or else it won’t be carried across the membrane
competition: decreases transport rate when another molecule is fighting to be transported in the same transport as another molecule
saturation: when transport reaches a maximum rate + all the carrier binding sites are filled with substrate
Give the 4 types of membrane proteins based on function.
1) membrane transport
2) structural proteins
3) membrane enzymes
4) membrane receptors
what are uniport carriers?
move one molecule
what are cotransporters?
move more than one type of molecule
what are symport carriers?
move molecules in the same direction
what are antiport carriers?
move molecules in opposite directions
what is primary (direct) active transport?
uses ATP directly (ex: Na, K, ATPase)
what is secondary (indirect) active transport?
Uses potential energy stored in concentration gradients of one molecule to push another molecule against its gradient (ex: SGLT)
How many Na+ and K+ transported in the Na+-K+-ATPase?
3 Na+ out to ECF
2 K+ in to ICF
Compare phagocytosis, endocytosis, and exocytosis.
Phagocytosis: uses actin microfilaments and myosin motor proteins to engulf particles in large vesicles
exocytosis: same as phagocytosis except it engulfs smaller things like fluid, ECF, and solutes
endocytosis: removes something from inside the cell (ex: membrane removed from the cell surface)
Explain transcellular transport, paracellular transport, and transcytosis as they apply to epithelial transport.
transcellular transport: goes through the cell (by simple diffusion or transporters)
paracellular transport: goes between cells (have to be small to move)
transcytosis: use vesicles to cross cells
what is the definition of absorption?
Transport from lumen to ECF
what is the definition of secretion?
Transport from ECF to lumen
Explain what it means for a cell to have a resting membrane potential difference.
- Resting is the steady state
- Potential energy stored in the electrochemical gradient
- Difference in electric charges inside and outside of the cell
Explain how changes in ion permeability change membrane potential, giving examples.
Depolarization –> getting more positive
- ex:
Repolarization –> go from depolarization to RMP
-ex:
Hyperpolarization –> get more negative
- ex:
