transport Flashcards
What factors affect diffusion
- Temperature
- Diffusion distance
- Surface area
- Size of molecule
- Concentration gradient
What is the definition of diffusion
is it passive or active
Movement of particle from an are of high concentration to low concentration along the concentration gradient
passive
What is facilitated diffusion and what does it transport
is it passive or active
It transports water soluble molecules that cannot pass through the phospholipid bilayer
e.g. some polar molecules
passive
How is diffusion facilitated
By channel and carrier proteins that are complimentary to the molecule and these can sometimes become saturated
What is the definition of facilitated diffusion
Movement of particles from high to low concentration, across a membrane by means of a channel or carrier protein
How is a cell wall important in osmosis
It keeps the plant turgid and stops it from lysis (splitting)
What is water potential and how is it measured?
what is the water potential of pure water?
The potential energy of water in a system compared to pure water
- measure if Kpa (pressure), and is ALWAYS NEGATIVE , with a maximum value of 0
water potential of pure water is 0 kpa
what is the osmotic/solute potential and what is the pressure potential
osmotic/solute potential is inversely proportional to the amount of solute dissolved
pressure potential can be exerted by a cell wall and can bring the water potential to 0
what is the definition of osmosis
is it passive or active
The net movement of water from a high water potential to a low water potential across a partially permeable membrane.
passive
what happens to water potential as the amount of :
solute concentration goes up
pressure potential goes up
- Water potential goes up
- Water potential goes down
what is the definition of active transport and what are the 2 types
particles move from an area of low concentration to high concentration through the use of ATP against the concentration gradient
primary active transport
secondary : co transport
What happens in primary active transport
- ATP binds to the carrier protein
- ATP is hydrolysed and donates a phosphate group to the carrier protein (also the molecules/ions needed to be transported)
- This causes the carrier protein to change shape
- The substance can now be carried over the membrane
3 sodium ions out (+)
2 potassium ions in (+)
What happens in secondary active transport / co transport
happens in phloem loading
1. ions are pumped across the membrane by primary active transport
2. A carrier protein facilitates the diffusion of the ion back across the membrane to the phloem
3. Another chemical is associated with the ion and is brought in with it
What is exocytosis and endocytosis and when do they happen and how
exocytosis - going out
endocytosis - going in
vesicles fuse with the plasma membrane and releasing its contents
happens in bulk transport (transportation of big molecules)
How does temperature effect membrane permeability
More kinetic energy so phospholipids will have more energy to move so there’s an increase in membrane permeability
What happens to membrane permeability at different temperatures
- 0 degrees or below - phospholipids are packed closely together but channel/carrier proteins change shape/deform increasing permeability
- 0-45 degrees - membrane is partially permeable as phospholipids move freely. As temperature increase the membrane permeability increases
- 45 degrees and above - Membrane becomes highly permeable, proteins start to deform, water inside cell expand putting pressure on the membrane
How does the solvent concentration effect membrane permeability
increase in solvent concentration increases permeability
What are channel proteins
- water filled pores
- Allow polar ions to diffuse through the membrane
- control the exchange of ions
what are the factors effecting the rate of osmosis
- water potential gradient - higher gradient = more osmosis
- Thickness of the exchanging surface
- Surface area of exchanging surface
what are the factors effecting the rate of active transport
- the speed of individual carrier proteins
- The number of carrier proteins present
- The rate of respiration in the cell and the availability of ATP
What are the functions of the cell membrane
- separation between extracellular fluids and internal organelles
- communication with other cells
- transport of materials
- structural support
- recognition of external substances
What happens if the cell in osmosis is exposed to an
- isotonic
-hypertonic
or hypotonic
solution
Isotonic - Water concentration is the same inside and outside the cell so movement of water will happen at the same rate
Hypertonic - outside the cell has a higher solute concentration than the inside so the cell will shrivel due to loss of water
hypotonic - inside the cell there is a higher concentration of solute so the cell will become turgid and could burst
what can and cannot move across the cell membrane
polar and non-water soluble molecules can pass through the membrane
water-soluble molecules such as sugars, amino acids and proteins cannot leak out of the cell and unwanted water-soluble molecules cannot get in along with non polar molecules
what is co transport
