Movement across membranes Flashcards
What is the definition for simple diffusion?
net movement of particles fro an area of high to low concentration (through a phospholipid bilayer)
What are the key requirements for simple diffusion?
all particles are constantly in motion, motion is random, particles constantly bouncing off eachother
Why do oxygen and carbon dioxide pass directly though membranes unassisted?
non polar
small
uncharged
What is Ficks law?
(SA x conc. gradient) / diffusion distance
What is facilitated diffusion?
passive movement (high to low conc.) across transmembrane channels that span membrane
doesn’t require ATP
What are the transmembrane channels?
channel protein
carrier protein (no ATP used)
Channel vs carrier protein?
channel: core - water filled
transports ions - charged
carrier: change shape
transports glucose - larger
What are water aquaporins?
allow diffusion of water through protein channel
water passes through simple diffusion
What factors increase rate of facilitated diffusion?
conc. gradient
no. of proteins
What factors increase rate of simple diffusion?
conc. gradient
surface area
diffusion distance
Why is facilitated diffusion a passive process?
no ATP required
How does active transport differ from passive transport?
requires ATP
Low to high conc.
How does active transport work with a carrier protein?
molecule/ion binds to carrier protein
ATP binds to protein and splits
Carrier protein changes shape to transport molecule or ion from one side of membrane to other
phosphate molecule released from protein and protein reverts to original shape
ADP reforms ATP
