movement of substances Flashcards
factors affecting diffusion
-smaller particles diffuse faster
-diffusion takes place faster through thin membrane
-SA:V
-shorter distance between two regions
-increase in temperature as particles have more kinetic energy
why are plant cells most suitable in hypotonic solution
-uptake of water is eventually balanced by elastic wall pushing back on cell
why is animal cell most suitable in isotonic solutions
-no special adaptation to offset uptake or loss of water
what happens when animal cell is in hypotonic solution
-cytoplasm has lower water potential than outside solution
-water diffuses into cell through osmosis across the partially permeable cell membrane
-as water enters the cell, cell swells as it does not have cell wall to protect it and burst
what happens when animal cell is in hypertonic solution
-as cell shrink, it crenates and become dehydrated and dies
what happens when plant cell is in hypotonic solution
-cell sap has lower water potential than outside solution
water diffuses into cell by osmosis
-water enter cells, vacuole increase in size and pushes cell contents against cell wall and cell becomes turgid
-strong and inelastic cell wall prevents over expansion of cell by exerting opposing pressure as water enters cell, prevents entry of more water
-protect cell and does not burst
what happens when plant cell is in hypertonic solution
-as cell loses water, vacuole decrease in cell and becomes plasmolysed
definition of facilitated diffusion
-diffusion of molecules and ions across cell surface membrane that is facilitated by protein channels within membrane down a concentration gradient
how do channel proteins function
-open up pores lined with polar groups across the membrane allowing entry and exit of substances including charged ions
how do carrier proteins function
-allow larger polar molecules like sugars and amino acids to diffuse across membrane
-particular molecule attaches to carrier protein at binding site causing it to change shape and deliver molecule through membrane
difference and similarity in diffusion and facilitated diffusion
-rate depends on concentration gradient, specific molecules diffuse faster
-occur in either direction, diffuse faster in one direction
-equilibrium reached when concentration is equal
-energy from ATP not required
example of diffusion and facilitated diffusion
-oxygen moving through plasma membrane
-glucose molecules moving into cells
carrier proteins that require ATP
-energy required for membrane protein to change shape and deliver molecule
-have mitochondria, high rate of respiration
factors that affect active transport
-temperature faster
-oxygen concentration higher
-presence of poisons like cyanide
processes that involve active transport
-nerve impulse transmission
-muscle contraction
-absorption of amino acids in gut and mineral salts by roots
-excretion of urea in kidney
