Movement of Substance In and Out of Cells Flashcards
What are the 3 types of movement of substances?
active transport
diffusion
osmosis
What is active transport?
movement of particles from an area of low conc. to high, across a membrane, requires energy
What is osmosis?
movement of water from a dilute solution (high water potential) to concentrated solution (low water potential) across a partially permeable membrane
What is diffusion?
movement of particles from an area of high conc. to low
Do single-celled organisms need a transport system?
no, they have large surface area:volume ratio
Do multi-celled organisms need a transport system?
yes, they have a small surface area:volume ratio
they have specialist exchange organisms to obtain all they need & have circulatory systems to move nutrients/oxygen around
How does a cell become shrivelled?
- higher water potential inside cell
- water moves out of cell by osmosis
- cell shrivels up
How does a cell become flaccid?
- water is lost from cell
- vacuole shrinks & loses its shape
How does a cell become normal?
- no net movement
- water moves at same rate since there is an equal water potential
- cell stays same
How does a cell become lysed?
- higher water potential outside cell
- water moves into cell by osmosis
- too much moves in & it bursts
How does a cell become turgid?
- water enters by osmosis
- vacuole swells & pushes against cell wall
What factors affect the rate of diffusion?
- temperature - particles have more energy & move faster, increased rate of diffusion
- diffusion distance - wider the barrier, slower the rate of diffusion
- surface area - higher means faster diffusion
- concentration gradient - difference in concentration, higher difference = faster diffusion
How does active transport work?
- protein pumps in cell membrane
- energy from ATP is used to pump substances across membrane, against concentration gradient
- substances moved can’t move back
What are some examples of things that use active trasnport?
- root hair cells in plants - used to obtain mineral ions from soil
- small intestine - absorption of glucose into blood
- kidney - reabsorption of glucose from glomerular filtrate in PCT
What is used to show osmosis and why?
visking tube
- mimicks the partially permeable membrane
What osmosis happens when a plant cell is in water?
- water moves into cell
- cytoplasm pushes against cell wall
- makes cell turgid - provides support
What osmosis happens when a plant cell is in strong salt solution?
- water moves out of cell
- cytoplasm pulls away from cell wall
- cell is plasmolysed
What molecules/substances can’t cross the membrane?
large molecules
charged particles
What organelle controls what goes in & out the cell?
cell membrane
What molecules enter the cell for respiration but leave for photosynthesis?
glucose
oxygen
