diffusion Flashcards
(89 cards)
define ‘diffusion’
diffusion is molecules that are going from an area of high concentration to an area of low concentration, going down a concentration gradient until they are equally spread apart.`wha
what feature of the phospholipid bilayer prevents polar and charged particles crossing a membrane
the hydrophobic tails
name 2 gases that can cross the membrane by simple diffusion
oxygen - O2
carbon dioxide - CO2
name 2 vitamins that can cross the membrane by simple diffusion and why they can
Vitamin A and D as they are lipid soluble which allows them to pass through bilayer without needing membrane proteins
explain how lipid solubility and the size of the molecule affects the rate of diffusion
lipid soluble molecules diffuse more easily than polar or charged molecules as they can dissolve and pass through the lipid bilayer of membrane which is non polar.
Smaller molecules diffuse faster than larger molecules as they can more easily diffuse through the pores
explain how the surface area of a cell membrane affects the diffusion rate
the larger the surface the more molecules have room to diffuse across in a given time
what adaptation of the cell membrane increases surface area
having microvilli
how does diffusion path affect the rate of diffusion
the shorter the diffusion path the faster the rate of diffusion
How does concentration gradient affect the rate of diffusion
the greater the difference in the concentration of molecules in 2 areas the more molecules diffuse in a given time
explain how temperature affects the rate of diffusion
a higher temperature increases the rate as molecules or ions have more kinetic energy.
what are 2 similarities between simple and facilitated diffusion
They are both a passive process so don’t require energy in the form of ATP and they both involves molecules that move down a concentration gradient
what are 2 differences between simple and facilitated diffusion
simple diffusion doesn’t require membrane proteins whereas facilitated diffusion uses channel or carrier proteins and simple diffusion is used mainly for small non polar molecules whereas facilitated diffusion is used for large polar molecules
name 2 substances that could be transported by facilitated diffusion
glucose and amino acids
what is co transport
a type of diffusion that brings molecules and ions into cells together on the same transport protein molecule.
an example of co transport
the glucose-sodium co- transport
what happens when there is a high concentration of ions or molecules
there will be a net movement away from that area until there is a uniform distribution
list the things that affect the rate of diffusion
-concentration gradient
-thickness of exchange surface of distance of travel
-surface area of membrane
-size of the molecule being diffused
-nature of the diffusing molecule
-temperature
how does the thickness of exchange surface or distance of travel affect the rate of diffusion
the thinner the membrane or shorter the distance the more molecules diffuse in a given time
what is the equation the rate of diffusion can be expressed by
rate of diffusion = (surface area x difference in concentration) / length of the diffusion path
how does the size of the molecule being diffused affect the rate of diffusion
as the smaller molecules diffuse faster than large molecules
how does the nature of the diffusing molecule affect the rate of diffusion
as fat soluble molecules diffuse faster than water soluble molecules and non polar molecules diffuse faster than polar molecules
Why can’t ions and molecules such as glucose not pass through the cell membrane
as they are relatively insoluble in the phospholipid bilayer
what is facilitated diffusion
the passive process of transferring molecules or ions down a concentration gradient across a membrane by protein carrier molecules in the membrane
where does facilitated diffusion occur
at specific sites on the plasma membrane where there are transport protein molecules
