| K+ | ___ gradient is a major determinant of electrical excitability |
| 1. simple diffusion
2. faciliated diffusion
3. osmosis | 3 types of passive transport |
| random movement of particles | what is Brownian Motion? |
| higher; lower
-but not necessarily on purpose | particles move from area of ____ concentration to areas of ____ concentration. |
| 1. size
2. lipid-solubility
3. charge | membrane permeability based on (3): |
| -no energy needed
-no carrier proteins needed
-lipid-soluble molecules easily cross
-other small lipid-insoluble can use channels | characteristics of simple diffusion |
| 1. gated= some stimulus must open in
2. non-gated= tunnel | two types of channels |
| 1. voltage-gated channels
2. ligand-gated channels | two types of gated channels |
| Human Aquaporin I | ex of non-gated tunnel |
| 1. size
2. shape
3. charge | channels are selectively permeable based on (3): |
| 1. at resting conditions, gates are closed
2. stimulation
-either alternation in membrane voltage or binding of ligand
3. channel opens | summary of control of diffusion |
| TRUE | T/F: potential has to reach a threshold to open the gate. |
| FALSE
-all or none | T/F: channel gates can halfway open. |
| 1. membrane permeability
2. concentration difference across the membrane
3. effect of electrical potential | factors influencing diffusion (3): |
| fick's law | what concept related to concentration differences? |
| nernst equation | what concept relates to electrical potential? |
| 1. thickness of membrane
2. lipid solubility of substance itself
3. # of protein channel available
4. size of diffusing substance | membrane permeability in diffusion depends on (4): |
| rate of diffusion across cell membrane is proportional to concentration difference & permeability of partition to solution | concentration difference in diffusion |
| rate= permeability coefficient x (Ci-Co)
-holds true for uncharged molecule | Fick's Law |
| -movement is not random when electrical force influences motion
-have to take into account concentration difference and electrical pull
-equilibrium develops b/w concentration gradient & electrical gradient rep'd by Nernst Equation | effect of electrical gradient in diffusion |
| equilibrium that develops b/w concentration gradient and electrical gradient
- EMF= (+/-)61logCi/Co | Nernst Equation |
| -occurs in direction of electrochemical gradient
-no energy required
-movement of solutes via carrier proteins
-can become saturated | characteristics of facilitated diffusion |
| FALSE | T/F: carrier proteins and channel proteins are the same. |
| -double-gated binding sites
-finite # of binding sites (limit on transport rates)
-3 types (uni-, sym-, antiporter) | characteristics of carrier proteins |
| 1. uniporter= one molecule
2. symporter= 2 diff molecules in same direction
3. antiporter= 2 diff molecules in diff directions
2&3 most common | 3 classifications of carrier proteins |
| -water moving from area of high water to low water OR low solute to high solute
-net movement can cause cell to shink or swell
-can create pressure diff if solute concentration REALLY differs | characteristics of osmosis |
| water will only push until pressure of gravity on solute side balances pressure of water movement
- hydrostatic pressure = osmotic pressure | concept of osmotic pressure |
| 1. movement of molc/ions "uphill" against concentration gradient
2. can establish/maintain concentration gradient
3. requires energy
4. has specificity, saturation, & competition bc of carrier proteins | characteristics of active transport (4) |
| 1. primary
2. secondary | types of active transport |
| 1. uses ATP to move molecule "uphill" against concentration gradient
2. ATP-powered pumps used for this | characteristics of primary AT |
| 1. ATP binding sites on cytosolic/cell sides
2. ATP -> ADP + Pi when molecules/ions transported | characteristics of ATP powered pumps |
| 1. p-pumps
2. f-pumps
3. v-pumps
4. abc-pumps | four classes of ATP powered pumps |
| Na+/K+ pump
- 2 K+ in/ 2 Na+ out/ 1 ATP used
-maintains resting membrane potential
-present in all cells of the body | example of MOST important p-pump & characteristics |
| H+-K+ pump
-in stomach, kidney, intestines
-2 H+ in/ 2 K+ out/ 1 ATP used | example of a lesser important p-pump |
| Ca2+ pump aka PMCA
- found in possibly all cells & ER & SR
- CA2+ out of cells | another example of lesser important p-pump |
| -does not use ATP directly
-uses energy of downhill movement of other molecule | characteristics of secondary active transport |
| 1. cotransporters (symporters)
2. exchangers (antiporter/countertransport) | two major types of secondary active transport |
| Na+ Glucose transporter
-energy to move glucose against concentration gradient comes from NA+ electrochemical gradient
- glucose piggybacking on Na+ passively going in | example of secondary active transport |
