movement of substances into and out of cells Flashcards
what is diffusion?
the random movement of particles from an area of high concentration to an area of lower concentration
what 4 factors affect the rate of diffusion?
- temperature
- conc gradient
- distance
- surface area to volume ratio
how does temperature affect the rate of diffusion?
at higher temperatures, molecules have more kinetic energy and move faster so diffusion occurs faster
how does concentration gradient affect the rate of diffusion?
- if there is a large difference in concentration between 2 areas, molecules will diffuse from the higher to the lower concentration quickly
- if concentration gradient is smaller, diffusion will happen more slowly
how does distance affect the rate of diffusion?
diffusion takes longer if the molecules have to travel further
how does SA:V ratio affect the diffusion distance?
surface area is very large compared to the distance the molecules must travel- speeds up the rate of diffusion
what is water potential?
a measure of the concentration of free water molecules in a solution
what is osmosis?
the net movement of water molecules from an area of high water potential to an area of low water potential across a partially permeable membrane
what is an isotonic solution?
the solution outside the cell has the same water potential as inside the cell- no net movement
what is a hypotonic solution?
the solution outside the cell has a higher water potential than inside the cell- net movement of free water molecules into the cell
what is a hypertonic solution?
the solution outside the cell has a lower water potential then inside the cell- net movement of free water molecules out of the cell
when will plant cells become turgid?
in a hypotonic solution
when will plant cells become flaccid?
in an isotonic solution
when will plant cells become plasmolyzed?
in a hypertonic solution
when do plants wilt?
when there is not enough water to fill their cells and therefore the cytoplasm shrinks from the cell wall
why is active transport used by organisms?
to transport substances against the concentration gradient
in order to transport substances against the concentration gradient what does the organism need?
- special carrier proteins in the cell membrane
- these use ATP to provide the energy to move substances across the membrane against the concentration gradient
when is active transport used in humans?
glucose is absorbed by active transport in the small intestine
when do plants use active transport?
in their root hair cells to absorb mineral ions
what is active transport?
the movement of molecules from an area of low concentration to an area of high concentration using ATP
what do multicellular organisms have that maximise the exchange of materials?
exchange surfaces and organ systems
what are the gas exchange organs in fish?
gills
how do these organs increase the efficiency of materials?
- having a large SA to increase the rate of transport
- a short diffusion distance
animals have well ventilated gas exchange surfaces to maintain what?
steep concentration gradients
