2.2 Flashcards
diffusion
net movement from regions of greater concentration to regions of lower concentration
random movement towards equilibrium
diffusion rate factors (5)
size and mass of molecules or ions (larger and heavier = slower)
temperature of the solution (higher temp. = faster movement)
density of solution (higher density = higher rate)
concentration gradient
area and distance (shorter = higher rate)
passive transport
simple diffusion
facilitated diffusion
NO energy input
active transport
primary active transport
secondary active transport
ATP needed
simple diffusion
small uncharged molecules can diffuse through the membrane down the concentration gradient
osmosis
diffusion of water molecules through a membrane down its concentration gradient
water diffuses from hypotonic to hypertonic
hypertonic v. hypotonic solutions
hypertonic solutions have a higher concentration of solute
hypotonic solutions have a lower concentration of solute
facilitated diffusion
diffusion of polar and charged molecules facilitated by channel or carrier proteins
channel proteins
form a tunnel across a membrane through which certain molecules can pass
allow certain substances to diffuse through the membrane down their concentration or electrochemical gradient
AKA integral membrane protein
ion channels
channel proteins with hydrophilic pores
ligand-gated channels
type of ion channel
open in response to a stimulus molecule (ligand) so that specific polar molecules can pass through
voltage-gated channel
open in response to a change in electrical potential (voltage) causing Ca2+ influx
aquaporins
channel proteins that facilitate the rapid movement of water across the membrane
carrier proteins
bind a polar molecule and facilitate its diffusion down the concentration gradient
glucose transporter
carrier protein
glucose binds to the glucose transporter, causing it to change shape and release glucose on the other side
rate of diffusion (facilitated)
channel: linearly increases
carrier: increases then reaches an asymptote
active transport
moves substances against their concentration or electrochemical gradient
requires energy
primary active transport
Na+-K+ pump brings two K+ ions into the cell and exports 3 Na+ ions using energy from ATP
secondary active transport
an electrochemical gradient generated by primary active transport is used to move a solute against its concentration gradient
active transport membrane proteins
uniporter, symporter, antiporter
