Transport Processes Flashcards
Transport Processes: Diffusion, Osmosis & Active Transport
What is diffusion?
The net movement of molecules and ions from a region of higher to lower concentration, down a concentration gradient, as a result of their random movement.
What factors affect the rate of diffusion?
- Surface area : volume ratio (+)
- Temperature (+)
- Diffusion distance (−)
- Steepness of concentration gradient (+)
- Diffusion medium (slowest in solids, fastest in gas)
- Size of molecules/ions (−)
What are some examples of diffusion?
- Nutrient (glucose, amino acid) uptake into cells
- Gaseous exchange
- Loss of water vapour (transpiration) in leaves
What is hypertonicity and hypotonicity?
Hypotonic > higher water potential, dilute solution
Hypertonic > lower water potential, concentrated solution
Used for osmosis in animal cells
Isotonic > equal concentration
What is osmosis?
The net movement of water molecules from a region of higher to lower water potential through a partially permeable membrane
What happens when an animal cell is placed in a solution of higher/lower water potential compared to its cytoplasm?
Higher WP > expands and bursts
Lower WP > shrinks and becomes crenated
What happens when a plant cell is placed in a solution of higher/lower water potential compared to its cytoplasm/cell sap?
Higher WP > expands and becomes turgid
Lower WP > shrinks and becomes plasmolysed, tissue becomes flaccid
What is turgor pressure?
The pressure exerted outwards on the plant cell wall due to water in the cell.
What is Active Transport?
The movement of particles through a cell membrane from a region of lower to higher concentration using the energy from respiration.
What organelle can you expect to find more of in cells that perform active transport?
Mitochondria as it helps the cell to release more energy through respiration for active tranport.
Fairly niche question, could appear using given examples e.g. villi.
What effect does heat have on osmosis?
Heat damages the partially permeable membrane required for osmosis, causing it to become more permeable, allowing solute particles to also diffuse through, so osmosis can no longer occur.
What effect does heat have on active transport?
Heat causes the transport proteins in the cell to denature, so active transport cannot occur as it relies on a functioning transport protein.
What term best describes cell R in this diagram?
Plasmolysed
Do not use “crenated” as the cell is a plant cell (has cell wall).
goofy ahh question ik
A bag that is made of a partially permeable membrane is placed in a solution. If the mass of the bag increased, was the water potential of the solution higher or lower than that of the inside of the bag at first?
Higher
