Movement Of Substances Flashcards
(8 cards)
What is a concentration gradient?
A concentration gradient is the difference in concentration between two regions
What is Diffusion
Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient
What are the factors which affect the rate of diffusion?
Diffusion distance
- the shorter the diffusion distance, the shorter the time needed for the substance to travel is and hence rate of diffusion increases.
E.G. Trachea in the lungs, Root hair cell
Surface area-to-volume ratio
- the greater the surface area-to-volume ratio of a cell, the higher the rate of diffusion.
E.G. microvilli in small intestine, root hair cells.
To calculate total surface area, calculate the surface area of one surface first before multiplying by the amount of surfaces the object has. Volume = Length x Breadth x Height
What is osmosis?
Osmosis is the movement of water molecules from a region of higher water potential to a region of lower potential down a water potential gradient and across partially permeable membrane.
What are some of the effects of osmosis on cells?
Cell in Solution of higher water potential:
Plant cell = expand or swell, becomes turgid. Cytoplasm pushes against cell wall, vacuole increases in size. (will not burst due to cell wall)
Animal cell = swell or burst
When cells are placed in a solution of the same concentration, nothing happens.
Cell solution of lower water potential:
Plant cell = plasmolysis occurs. Cell decreases in size, cytoplasm shrinks away from cell wall, vacuole decreases in size. Cell becomes flaccid or limp.
Animal cell = cell crenates, shrinks and spikes appear on the cell. Become dehydrated and eventually dies.
What is Active Transport?
Active Transport is the process in which energy is used to move the particles of a substance against the concentration gradient across a partially permeable membrane, from a region of lower concentration to a region of higher concentration.
What are the differences between diffusion and osmosis?
Diffusion | Osmosis
Net movement of particles | Net movement of water molecules
Down a concentration gradient | Down a water potential gradient
Presence of partially permeable membrane not needed | presence of partially permeable membrane needed
What are the differences between diffusion and active transport?
Diffusion | Active Transport
Region of higher concentration to region of lower concentration | Region of lower concentration to a region of higher concentration
Down a concentration gradient | Against a concentration gradient
Energy from respiration not required | Energy from respiration required
Partially permeable membrane not required | Partially permeable membrane required
