Chapter 4 Flashcards
Diffusion of small particles
Moves DOWN its concentration gradient (electrochemical). Requires no additional energy
Simple diffusion
No binding needed (not carrier mediated)
What affects simple diffusion?
Concentration difference, electrical gradient, pressure, and temperature
Simple diffusion through phospholipid bilayer
The more lipid soluble the higher the concentration difference, the faster the diffusion rate
What passes through a phospholipid bilayer using simple diffusion?
Gasses (CO2, O2, NO), alcohol, and small lipid solubles (steroid hormones, testosterone, estrogen, progesterone, cortisol)
Simple diffusion through a pore
Usually for water and are always open
What are the simple diffusion pores for water called?
Aquaporins
Simple diffusion through a channel
Can be opened or closed. Selective permeability based on charge, shape, & diameter
Mechanically gated channels
Opened or closed in response to changes in pressure
What is another name for mechanically gated channels?
Pressure gated
What uses mechanically gated simple diffusion channels?
Most mechanoreceptors. Baroreceptors, joint proprioceptors, muscle spindles, golgi tendon organs, meisner’s, meckel’s, pacinian
Ligand gated channels
Opened or closed when a molecule binds to a membrane receptor
What are examples of ligand gated channels?
Nicotinic & muscarinic receptors, neurotransmitters, protein hormones, chemoreceptors, & chemical senses (taste and smell)
Voltage gated channels
Opened or closed in response to a change in the electrical charge/potential of the nearby membrane
Where are voltage gated channels used (location)?
Axon hillock & along the axon during action potential
How does a voltage gated channel work?
They are shocked open or are on a timer. When opened they are snapped open. Na+ rushes in causing depolarization which then snaps the channel closed + triggers K+ channels
Facilitated diffusion
Binding required. Carrier mediated which is limited by stereospecificity
Examples of facilitated diffusion
Glucose uptake into cells using a GLUT4 protein
What activates facilitated diffusion in all cells EXCEPT neurons?
Insulin
Is simple or facilitated diffusion faster?
Facilitated until you hit V max
Active transport
Moves a molecule against its concentration gradient. Requires an energy source. Carrier mediated. Subject to saturation/transport max, stereospecificity + competition
Primary active transport
Uses ATP to pull molecules against their concentration gradient (pumps)
Sodium potassium pump (ATPase pump)
Moves Na+ and K+ against concentration gradient. Slightly electrogenic.
How many and in what direction does the ATPase pump move sodium and potassium?
3 Na+ OUT. 2 K+ IN
What pump can run in reverse to create ATP, when needed?
Sodium-potassium pump
What pump is the main burner (user) of ATP in most cells?
ATPase pump
Calcium Pump
Pumps calcium OUT of cells + into sarcoplasmic reticulum
H+ ion pump
Parietal cells of stomach to build gastric acidity. Intercalated cells in kidney nephron to balance acid-base
Secondary active transport
Uses energy stored as a concentration gradient
Synport (co-transport)
When 1 molecule pulls another molecule into the cell with it
What are examples of co-transport?
Sodium glucose symporter, amino acid cotransport
Antiport (counter transport)
As a molecule moves into the cell and another molecule moves out of the cell
What are examples of antiport?
Na+ moves into the cell so Ca2+ can move out. Chloride moves into RBCs and bicarbonate moves out
Carrier mediated transport
Physically binding to a transmembrane protein to get in/out of cell
What type of transport uses carrier mediated transport?
Facilitated diffusion + active transport
What are the limitations of carrier mediated transport?
Stereospecificity, competition, & transport maximum (saturation)
Stereospecificity
D vs L isomer
Competition
2 similar molecules competing for a binding site
Transport maximum (saturation)
Point where all the proteins are working as fast as possible to move molecules across
Sodium transport
Simple diffusion to enter epithelial cell. Active transport to get out of the cell
Potassium transport
Need active transport to pull it into the cell. Simple diffusion to exit the cell
Water transport
Osmosis
Movement of larger molecules
Endocytosis: pinocytosis
Forces acting on water crossing a membrane
Usually aquaporins allow water to freely move into and out of cells. Hydrostatic pressure pushes water. Osmotic pressure
example of regulation of CO2 & pH: O2
high levels of O2 in the lungs facilitate loading hemaglobin. O2 levels lower and easily detaches when it gets to tissues
example of regulation of CO2 & pH: CO2
diffuses out of cells down concentration gradient through interstitial fluid, capillary membranes and into RBCs
where is CO2 processed?
red blood cells
what buffers hemaglobin in RBCs?
H+
what acts as a buffer in the plasma?
bicarbonate
