Diffusion
-the movement of molecules from one location to another across a membrane
-always proceeds from higher to lower concentrations
Magnitude
The _______ of diffusion is the same as direction
Temperate, mass, surface area, medium
What are some factors that influence the magnitude of diffusion?
higher temperatures will increase speed of molecules; increasing net flux
How does temperature affect diffusion & net flux?
slows the speed of molecules; slows net flux
How does the mass of the molecules affect diffusion & net flux?
greater surface area leads to greater diffusion; greater net flux
How does the surface area of the container affect diffusion & net flux?
denser the medium; slower net flux
How does the medium affect diffusion & net flux?
size of concentration gradient/ how dense molecules are
What does dC/dX represent?
size
What does Ds represent?
impacts diffusion rate
What happens when a membrane is present?
hydrophilic
Diffusion through membranes will cause diffusion rates for what types of molecules to decrease?
oxygen, carbon dioxide, fatty acids, steroid hormones, nonpolar molecules
Which substances diffuse rapidly through lipid portions of membranes?
Na, K, Cl, and Ca
Which substances must form water channels to enter or exit the cell?
Channels
-this machinery regulates the control and movement of ions into and out of a cell
channel gating; conformational change
The process of opening or closing is called _______; results from ____________
how often the channel opens, how long it stays open
What factors determine an ion passing through the channels?
ligand, voltage, mechanical
What are your types of Gated channels?
Ligand gated
-opens when ligands bind to it
Voltage gated
-opens when changes in membrane potential occur
Mechanically gated
-opens due to mechanical stress
transporter moves molecules down concentration gradient and across cell membrane; continues until concentrations are equal on both sides of membranes
How does facilitated diffusion work?
atp
Facilitated diffusion does not utilize ______ to move molecules
active transport
-this form of transport uses ATP to move molecules against the concentration gradient
pumps
Transporters that utilize ATP are called ?
Primary active transport
-this form of active transport utilizes a direct source of ATP
Secondary active transport
-uses an electrochemical gradient found across the plasma membrane to drive the transport process
Na+
-a major EXTRACELLULAR ion
K+
-a major INTRACELLULAR ion
3 Na+ out; 2 K+ in
How does the Na+/K+ ATPase pump work?
Cotransporters (symporters)
move molecules in the same direction
Countertransporters (antiporters)
move molecules in opposite directions
Osmosis
-the net diffusion of water across a membrane
aquaporins
What type of channel proteins diffuse water across a membrane?
Kidney
Which organ contains a high number of aquaporins inside of its cells?
increase in permeability
Increasing the number of aquaporins=?
Isotonic
-have the same concentration of solutes inside the cell as extracellular fluid
Hypotonic
-have lower concentration of solutes inside the cell compared to extracellular fluid
Hypertonic
-have higher concentration of solutes inside the cell compared to extracellular fluid
shrink
Hypertonic solution causes the cell to _____
swell
Hypotonic solution causes the cell to _____
transcellular transport
-movement that occurs through cells
paracellular transport
-movement that occurs around cells
tight junctions
Paracellular transport is minimized by ________ of epithelium
Claudins
How does our body regulate tight junctions? (i.e. make them less tight)
Epithelial transport
- molecules entering or leaving the body
-molecules moving between compartments
cross layers of polarized epithelial cells
In order for epithelial transport to occur, what must the molecule do?
2 step
Transcellular transport is a ________ process
3
Glucose transport from intestinal lumen or kidney tubule to ecf requires how many transport systems?
Sodium-glucose cotransporter
-brings glucose into cell against its gradient using sodium concentration gradient and kinetic energy
GLUT transporter
-transfers glucose to ECF by facilitated diffusion
Sodium-Potassium ATPase pump
-pumps sodium out of the cell to keep intracelluar sodium concentrations low
concentration differences, electrical differences
The direction and magnitude of ion fluxes depend on what ?