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.
What is high water potential called?
hypotonic
What is low water potential called?
hypertonic
plant cell in high water potential?
turgid
plant cell in low water potential?
flaccid
plasmolysis / plasmolysed
- cell membrane peels back from cell wall
animal cells in high water potential
burst
animal cell in low water potential
crenated
define active transport
active transport is the process in which energy is used to move the particles of a substance across a membrane against its concentration gradient, that is from a region where they are of higher concentration
where does active transport occur?
active transport only occurs in respiring living cells (abundant mitochondria) to release energy through oxidation of glucose
- dissolved mineral salts are taken up by root hair cells via active transport
- glucose and amino acids are absorbed by cells in the small intestines of humans via active transport
Criterion for difference in osmosis, diffusion, active transport
SMEG
Substance that is moving
presence of Membrane
Energy
type of Gradient (direction of movement)
difference in osmosis, diffusion, active transport
notes
