diffusion Flashcards
what is diffusion?
the passive movement of molecules or ions down a concentration gradient
from an area of higher concentration to an area of lower concentration
what are the factors affecting rate of diffusion?
surface area of membrane
length of diffusion pathway
Steepness of concentration gradient
temperature
size of diffusing molecule
nature of diffusing molecules
how does steepness of concentration gradient affect diffusion rate ?
the greater the difference in concentration of molecules in 2 areas the greater the rate of diffusion
how does length of diffusion pathway affect rate of diffusion?
the shorter the diffusion pathway, the faster the rate of diffusion.
Flattened cells, thinner membranes and less layers of cells decrease diffusion pathways.
how does surface area affect rate of diffusion?
a larger surface area gives more area in which diffusion can happen and increases the rate of diffusion.
Folds in the cell membrane increase the surface area.
how does size of diffusing molecule affect rate of diffusion?
smaller molecules diffuse faster than large molecules
how does temperature affect the rate of diffusion?
increased temperature increases rate of diffusion as molecules/ions have more kinetic energy
how does nature of diffusing molecules affect rate of diffusion?
fat soluble molecules diffuse faster than water soluble molecules
non polar molecules dissolve faster than polar molecules
what is the defintion of facilitated diffusion?
the passive transfer of molecules or ions from an area of higher conc to an area of lower conc (down concentration gradient) across a membrane by protein carrier molecules
channel proteins in facilitated diffusion:
channel proteins have pores lined with polar groups
channels are hydrophillic- water soluble ions can pass through
channels open and close according to the needs of a cell
carrier proteins in facilitated diffusion
allow diffusion of larger polar molecules such as amino acids and sugars
molecule attatches to its binding site on the carrier protein
carrier protein changes shape and releases the molecule on the other side of the membrane
