2B Diffusion, Osmosis & Active Transport Flashcards
Define diffusion.
NET MOVEMENT of particles from an area of HIGHER concentration to an area of LOWER concentration - the particles diffuse DOWN a concentration gradient
Is diffusion a passive or active process?
Passive
What is an active process?
Requires energy to happen
What is a passive process?
No energy is required for it to happen
What are the three factors that affect diffusion?
Surface area, concentration gradient and the thickness of diffusion pathway
How does the concentration gradient affect diffusion?
> HIGHER conc. grad. = HIGHER RATE of diffusion
However, diffusion SLOWS down ove time as the difference in concentration DECREASES with movement until an EQUILIBRIUM is reached
How does the surface area affect diffusion?
> The LARGER the surface area, the FASTER the rate of diffusion
How does the thickness of the diffusion pathway affect diffusion?
> The SMALLER the diff. path. width, the FASTER the rate of diffusion
Define facilitated diffusion.
The NET MOVEMENT of particles across a SEMI-PERMEABLE MEMBRANE from an area of HIGHER conc. to and area of LOWER conc. through a CARRIER/CHANNEL protein
Is facilitated diffusion an active or passive process?
passive
What is a carrier protein and how does it work?
> A protein in the membrane that moves LARGE molecules across it
a molecule ATTACHES to a carrier protein which causes it to CHANGE SHAPE
The molecule is then released on the OPPOSITE side of the membrane
What is a channel protein and how does it work?
> A protein that forms PORES in the membrane for CHARGED molecules to diffuse through
Different charged particles diffuse through different channel proteins
What two factors affect facilitated diffusion?
Concentration gradient and the number of channel/carrier proteins
How does the number of channel/carrier proteins affect the rate of facilitated diffusion?
> Once all proteins are in use, F.D can’t increase the rate even if there is an increase in the concentration gradient
The GREATER the number, the FASTER the rate of F.D
Define osmosis.
The diffusion of WATER MOLECULES across a PARTIALLY PERMEABLE MEMBRANE from an area of HIGH WATER POTENTIAL to an area of LOW WATER POTENTIAL
What is the potential of pure water?
0
What is the meaning of isotonic?
The water potentials of two solutions are equal so neither will lose/gain any water
Define hypotonic.
A solution with a water potential that is HIGHER than INSIDE the cell causing the cell to SWELL
Define hypertonic.
A solution with a water potential that is LOWER than INSIDE the cell causing the cell to SHRINK
What are the factors that affect the rate of osmosis?
Water potential gradient, thickness of exchange surface, SA of exchange surface
How does the water potential gradient affect the rate of osmosis?
> The HIGHER the gradient, the FASTER the rate of osmosis
> As osmosis occurs, the water potential gradient DECREASES so the rate of osmosis LEVELS off over time
Define active transport.
The use of ENERGY to move molecules and ions across PLASMA MEMBRANES using CARRIER PROTEINS and CO-TRANSPORTERS
What is the role of carrier proteins in active transport?
> Molecules ATTACH to the protein, it CHANGES SHAPE and causes the molecule to be RELEASED on the OPPOSITE side of the membrane
They usually move molecules from a LOW to a HIGH concentration
The movement requires ENERGY in the form of ATP - it is an active process
What is the role of co-transporters in active transport?
> they are a type of CARRIER PROTEIN that BIND to 2 molecules at one time
the concentration gradient of ONE molecule is used to move the other AGAINST its own conc. grad.
What three factors affect the rate of active transport?
Speed of individual carrier proteins, the number of carrier proteins, rate of cellular respiration and the availability of ATP
Define water potential
Liklihood of water molecules to diffuse out of or into a solution
Describe the chemical reaction the occurs to release energy from ATP
> A HYDROLYSIS reaction that breaks ATP down into ADP and an INORGANIC PHOSPHATE
It is the breaking of the HYDROGEN BOND that releases the energy
Why are sodium ions important in the transport of glucose from the ileum into the blood?
> Sodium ions diffuse from the LUMEN of the ILEUM into the INTESTINAL EPITHELIUM CELLS DOWN their conc. grad. through a sod.-gluc. co-transporter protein.
At the same time, the co-transporter carries glucos into the EPITHELIUM CELL AGAINST its conc. grad.
GLUCOSE is then able to DIFFUSE into BLOOD from the EPITHELIAL CELL
