Unit 3 Flashcards
Membrane transport
passive transport
movement of molecules down a concentration gradient or electrical gradient no atp required
simple diffusion
materials diffuse by inserting through the phospholipids and going to the other side, movement from high concentration to low concentration, spontaneous movement happens until you reach equilibrium
what molecules can do simple diffusion
gases and small hydrophobic molecules can cross membrane via simple diffusion
Facilitated diffusion
type of passive transport, requires assistance of specialized proteins in the membrane that help the substance cross bc molecules to be transported are either too large, polar or charged and need help cross membrane
Transporters/carriers
specific and selective, carrier proteins can change shape to move a target molecule from one side to the other, slower rate than channels
channels
like a pore, leave space in the center so the molecule can pass, specific based on size and charge, they span the membrane and make hydrophilic tunnels across
what does passage though a channel protein allow
allows polar and charged compounds to avoid the hydrophobic core of the plasma membrane which would slow or block entry into the cell
hypertonic environment
high solute concentration, low water concentration, low osmotic pressure
Hypotonic cell
cell has low concentration of solutes high concentration of water, high osmotic pressure
what is movement of water if you have hypertonic environment and hypotonic cell
solutes move into cell water moves out
hypertonic environment outside the cell
osmotic pressure is higher inside than outside the cell so water diffuses out and the cell shrinks
if hypotonic environment (low concentration solutes high water concentration) and hypertonic cell (high concentration solutes in the cell)
water diffuses into cell- tend to go from where there is more water (high osmotic pressure) to where there is less water (low osmotic pressure)
active transport
transport of substances against gradient, energy is needed to pump particles
two types of pumps for active transport
ATP powered and coupled pumps
coupled pumps
the flow of one substrate downhill releases the energy for the pump to transport another uphill (symporters and antiporters)
ATP Na+/K+ pumps
uses energy from ATP hydrolysis to transport Na+ and K+ against electrochemical gradient, this pump typically accounts for 30%+ of total ATP consumption
where are things moving with the Na-K ATPase pump
ATP driven NA pump in animal cell hydrolyzes ATP to ADP to transport NA out of cell and at the same time the pump couples the outward transport of NA to transport K into the cell
importance of the Na/K pump
maintains membrane potential, important in transmission of electrical signals in nervous tissue and muscle contraction
what happens if Na/K pump does not work
gradient would be lost, cell would eventually die
Ca2+ pump
keeps concentration of Ca low inside the cell, the Ca ATPase pumps Ca out of cell to restart nerve firing cycle
coupled pumps
flow of one molecule by passive transport is coupled (gives energy) to passage of another against concentration gradient by active transport, they use the energy stored in the gradients to move other substances against their on gradients
glucose Na+ symport
epithelial cells in the gut transfer glucose from lumen of digestive tube into epithelial cells, these celle possess a glucose Na+ symport which they can use to take glucose from lumen by active transport
H+ pumps
H+ gradients are used to drive membrane transport in plants fungi and bacteria- they rely on the electrochemical gradient of H+ to drive the transport of solutes into the cell
pumps in plants vs animals
in animals cells often the Na/K pump to drive active transport of solutes across the membrane, in plants bacteria and fungi cells H+ ATPase is used
