3: Movement in and out of cells Flashcards
Diffusion definition
net movement of particles from a region of their higher concentration to a region of their lower concentration
down a concentration gradient,
as a result of their random movement
why is diffusion of gases and solvents important?
Gases: allows gas exchange in organisms for metabolic reactions (respiration) to occur (substances move into and out of cells by diffusion through the cell membrane),
remove waste gases
Uptake of solutes from soil to plants
does not require energy
Where does the energy for diffusion come from?
factors: temp, conc, SA, diffusion dist
comes from the kinetic energy of random movement of molecules and ions
↑ Temp = ↑ rate of diffusion, molec gain KE = move faster
↑ conc gradient = ↑ rate, more random collisions occur
↑ SA = ↑ rate, more space available for particles to diffuse through
↑ Diffusion dist = ↓ rate, particles have to travel further
Osmosis definition
net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution), through a partially permeable membrane
What is the importance of water potential and osmosis on animal cells and tissues
Water within vacuole creates turgor pressure - pushes cell membrane against inelastic cell wall - provides support
Hypertonic solution
animal & plant cell
Water potential of solution < of cell
Animal: net movement of water OUT of cell - shrinks
Plant - out of cell - becomes PLASMOLYSED (cell membrane peels away from the wall)
concentrated solution outside
Hypotonic solution
animal & plant cell
Water potential of solution > of cell
Animal: net movement of water INTO of cell - bursts (lysis)
Plant - INTO of cell - becomes TURGID (does not burst = strong cell wall)
pure water/ dilute solution outside
Isotonic solution
animal & plant cell
Water potential of solution = of cell
No change in size
No net movement of water
Cell is FLACCID
equal solute concentration in/outside
Active transport definition
movement of
- particles through a cell membrane
- from a region of lower concentration to a region of higher concentration
- using energy from respiration
Why is active transport important?
In humans:
uptake of glucose by epithelial cells in villi and kidney tubules in nephron,
moves by carrier proteins
In plants:
uptake of ions and minerals by root hair cells
Carrier proteins
facilitate active transport
embedded in cell membrane
1. molecules from side with ↓ conc. g. bind to carrier protein
2. c. prot. changes shape using energy from respiration
3. forces molecules to move through membrane to side with ↑ conc., where it’s released.
