2 | MOS Flashcards
Definition of diffusion
Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration, down a concentration gradient (until equilibrium)
Properties of diffusion
- a passive process as energy is not required
- can take place with or without a membrane
- involves any type of molecule
- down a concentration gradient
- when particles have reached equilibrium between the 2 regions, the concentrations are the same and there will be no net movement of particles
Answering structure
- what is moving
- name of the process
- which gradient
- from where to where
What is net movement?
all particles move in constant random motion. Net movement occurs when there are more particles moving in a particular direction.
- due to a concentration gradient.
What is a concentration gradient?
- Concentration gradient is the difference in concentration between 2 solutions / regions
- the steeper the concentration gradient, the faster the rate of diffusion.
Role of MOS in nutrient uptake and gaseous exchange in humans
digestion:
- absorption of nutrients in the small intestine
respiration:
- exchange of gases between alveoli and blood
- exchange of gases between blood capillaries, tissue fluid and body cells
Role of MOS in nutrient uptake and gaseous exchange in plants
photosynthesis:
- exchange of gases between leaves and environment through stomata
transport in plants:
- absorption of mineral salts / ions by root hair cells
Factors affecting MOS
TCSD
Temperature
- increase in temp, increase in KE of molecules
Concentration gradient
- conc. grad is the diff in conc. betw 2 regions. Steeper the conc., higher the rate of diffusion
Size of molecules
- heavier molecules move more slowly than light molecules
Diffusion distance
- molecules do not have to travel far thus rate of diffusion is faster
Definition of osmosis
Osmosis is the net movement of water molecules, down a water potential gradient, across a partially permeable membrane (until equilibrium)
What is water potential?
- Tendency of water molecules to move from one place to another
- A dilute solution has a higher water potential
- A concentrated solution has a lower water potential
Definition of partially permeable membrane
allows some substances to pass through but not others
effects of osmosis
intake of water by cells
transport in plants
- absorption of water from surroundings by root hair cells
strip in water / concentrated sugar solution
- water / cell sap has higher water potential compared to cell sap
- net movement of water molecules in / out of the cell of the tissue strip down a wp gradient, through a ppm via osmosis.
strip in water
- swell, lengthen and become firm and turgid (effect)
- epidermal cells lined with a waxy cuticle impermeable to water
- expansion of cortical cells more than the epidermal cell will cause the strip to curl outwards
strip in concentrated sugar solution
- shrink, shorten and become soft and flaccid (effect)
- epidermal cells lined with a waxy cuticle impermeable to water
- shrinking of cortical cells more than epidermal cells cause strip to curl inwards.
