diffusion Flashcards
(37 cards)
what are the two types of diffusion
-simple diffusion
-facilitated diffusion
definition for diffusion
-the net movement of particles from a region of higher concentration to region of lower concentration
net movement of particles down a concentration gradient
describe why diffusion is a passive transportation process
diffusion moves molecules/ions down a concentration gradient
-diffusion does not require a metabolic source of energy such as ATP to transport molecules across the membrane
it instead relies on the energy from the natural, random movement of particles
explain why simple diffusion occurs and when it stops
-the particles of gas/liquid have kinetic energy
-their movement is random
-This creates an unequal distribution of particles between two areas
-This establishes a concentration gradient as substances diffuse from a region of higher concentration to a region of lower concentration
-Diffusion stops when an equilibrium is established, meaning that there is an equal distribution of particles between the two areas
what does an equilibrium being reached mean in terms of the movement of particles
particles are still constantly moving, however they now move equally in both directions
what factors affect the rate of diffusion
-steepness of concentration gradient
-surface area
-thickness of membrane
-temperature
-properties of molecules
what is the rate of uptake dependent on for simple diffusion
- the concentration
explain what is meant by the steepness of the concentration gradient
-firstly concentration gradient means the difference in the concentration of a substance between the two areas
-steepness-refers to the degree of a difference, the larger the difference between concentrations ,the steeper the concentration gradient
how does the steepness of the concentration gradient affect the rate of diffusion.
Explain your answer
The bigger the difference in the concentration of a substance , between the two areas ,the higher the rate of diffusion will be.
This is because the overall movement of particles from a region of higher concentration to a region of lower concentration will be larger.
explain how temperature effects the rate of diffusion
-as temperature increases, molecules have more kinetic energy thus move faster, this results in higher rate of diffusion
how does the thickness of a membrane affect the rate of diffusion. Explain
-the thicker the membrane, the longer the diffusion distance will be ,meaning that particles will collide more ,decreasing the rate of diffusion
describe how the surface area has an affect on the rate of diffusion
-the larger the surface area, the higher the number of molecules that can diffuse through at once, increasing the rate of dission
how can we increase the surface area
-the folding of a membrane increases the SA.
-like cristae in mitochondria
how does the SA:V ratio affect the rate of diffusion
-as the size of a cell increase, its SA:V ratio decreases.
This increases the diffusion distance of molecules and thus slows down the rate of diffusion
why is the rate of diffusion faster over short distances and slower over long distances
-particles move at high speed and are constantly colliding
-over short distances particles collide less thus rate of diffusion is faster
-over longer distances ,particles collide more thus the rate of diffusion is slower
what type of molecules are transported by facilitated diffusion and what by simple diffusion
-small, non-polar molecules such as oxygen are transported down a concentration gradient and across the membrane by simple diffusion
-larger and polar molecules like glucose are transported down a concentration gradient and across the membrane using carrier/channel proteins via facilitated diffusion
definition of facilitated diffusion
diffusion across a membrane using channel/carrier proteins
what are the two types of proteins involved in facilitated diffusion
-carrier proteins
-channel proteins
why are channel ad carrier proteins said to be specific
they are specific to and thus only transport one type of ion/molecule
difference between channel and carrier proteins
channel proteins do not change shape to transport substances across the membrane, whereas carrier proteins do
how do channel proteins control the exchange of charged/polar molecules
-they are ‘‘gated’’, meaning that a part of them moves to open and close the pore as the substance is being transported across the membrane
how do carrier proteins transport a polar molecule across the membrane
-the binding site of the carrier protein opens
-a molecules attaches to the binding site of the carrier protein which is embedded within the membrane
-this causes the carrier protein to change shape and release the molecule on the opposite end of the membrane
-the molecules are moved down a concentration gradient
is facilitated diffusion passive
yes
what other factors also affects the rate of facilitated diffusion
-the number of carrier/channel protein embedded in the cell membrane,
the higher the number of carrier/channel protein, the more molecules can be transported across at once, thus increasing the rate of diffusion
