passive transport

Question 1

factors affecting diffusion across a membrane

Answer 1

membrane thickness
surface area
temperature
concentration difference/gradient

Question 2

define simple diffusion

Answer 2

diffusion where there is no barrier/membrane

Question 3

factors affecting simple diffusion

Answer 3

temperature
concentration difference / gradient

Question 4

how does diffusion across a membrane work?

Answer 4

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

Question 5

define partially permeable

Answer 5

membranes that allow some molecules through

Question 6

how is alveoli adapted to increase the rate of diffusion

Answer 6

a massive surface area
a one cell thick lining –> short diffusion pathway
a very good blood supply –> concentration gradient

Question 7

how is villi adapted to increase the rate of diffusion

Answer 7

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