Transport Across Membranes Flashcards
What is diffusion?
The movement of particles from an area of high concentration to an area of low concentration down a concentration gradient.
Diffusion is a passive process that occurs through a selectively permeable membranes resulting in a uniform concentration of particles.
What is active transport?
Where molecules move from an area of low concentration to high concentration against the concentration gradient using energy from ATP.
What affects the rate of diffusion?
Temperature - higher the temp, faster rate as more kinetic energy
Concentration gradient - steeper gradient, faster rate as more particles moving from high conc to low conc
- surface area of exchanging surface, larger surface area, faster rate as more surface are to move across
- distance, shorter distance, faster rate as lest distance for p to move
- nature of cell membrane, more transport proteins means faster diffusion of polar particles as more facilitated d, more phospholipid bilayer, more diffusion of small non polar particles
- size and nature of particles, small particles Fisches faster as more kinetic energy, polar moves and lipid soluble rather than water soluble faster as move through bilayer
What is simple diffusion?
Where small non polar molecules diffuse through hydrophobic phospholipid bilayer. E.g. carbon dioxide
What is facilitated diffusion through a channel protein?
Ions diffuse through hydrophilic channel of protein from high to low conc as ion causes channel to open
What is facilitated diffusion through a carrier protein?
Where polar molecule diffuses through the hydrophilic channel from high to low conc by molecules attaching to binding site in carrier protein, which changes shape, molecule then moved through and carried protein moves back to original shape
How does active transport happen?
Phosphate group from ATP binds to site in carrier protein, molecule binds to to sites on carrier protein which changes shape and molecules move across memberane. Phosphate group released and carrier back to original form
What are similarities between active and passive transport?
- transport substances across the membrane
- use carrier proteins
What are differences between active and passive diffusion?
F: high conc to low conc
- no energy
A: low conc to high conc
- ATP required
What is osmosis?
Net movement of water from area of high water potential to low water potential down a water potential gradient across a partially permeable membrane
What’ is water potential of distilled water?
0kpa
What is definition of water potential?
Tendency of a solution lose water
What happens to water potential as solutes are added?
It decreases
What is solute potential?
Same as water potential, notated as ¥s
What is pressure potential?
A physical force (pressure) exerted on a solution/system
What is the equation for water potential
¥=¥s+¥p
What is a hypotonic solution?
Where the ¥ of solution is higher than the ¥ of cell. Water moves into cell by osmosis down a ¥ gradient
What is affect of hypotonic solution on animal and plant cell!
Animal: lysis occurs, and cell bursts, in blood cells this is haemolysis
Plant: becomes turgid due to cell wall does not burst
What is meaning of hypertonic?
¥ of solution is lower than ¥ of cell so water moves out of cell by osmosis
What is affect of hypertonic solution on animal and plant cells?
Animals: crenation, cell shrivels
Plants: becomes fully plasmolysed, where cell membrane and tonoplast of vacuole pull away from cell wall
What does isotonic meaning?
¥ of solution is equal to ¥ of cell so volume of water leaving will be at same rate as entering
What is effect of isotonic on animal and plant cells?
Animal: normal
Plant: becomes flaccid due to incipient plasmolysis, cell membrane just detaching from wall
What is co transport?
Type of facilitated diffusion that brings molecules and ions into cell together on same transport protein e.g. sodium glucose into blood in the ileum and kidney nephron
