passive transport Flashcards
factors affecting diffusion across a membrane
membrane thickness
surface area
temperature
concentration difference/gradient
define simple diffusion
diffusion where there is no barrier/membrane
factors affecting simple diffusion
temperature
concentration difference / gradient
how does diffusion across a membrane work?
particles passing through a phospholipid bilayer
can only happen if membrane is permeable
hydrophobic interior of membrane repels charged substances so they can’t pass through
define partially permeable
membranes that allow some molecules through
how is alveoli adapted to increase the rate of diffusion
a massive surface area
a one cell thick lining –> short diffusion pathway
a very good blood supply –> concentration gradient
how is villi adapted to increase the rate of diffusion
tiny, finger-shaped structure –> increase the surface area of small intestine
wall is one cell thick –> short diffusion distance and active transport
network of blood capillaries –> transport glucose and amino acids away from the small intestine in the blood
lacteal –> transports fatty acids and glycerol away from the small intestine in the lymph