DOA Flashcards
Diffusion
The net movement of particles from an area of higher concentration to an area of lower concentration
Osmosis
The movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration
Water will move across the membrane from a dilute solution (with lots of
Active transport
The movement of particles across a membrane against a concentration gradient (i,e from an area of lower to an area of higher concentration) using energy transferred during respiration
% (osmosis)
% change in mass = ((final mass - initial mass)÷ initial mass)
x 100
Factors effecting diffusion
Concentration gradient
The bigger the difference in concentration between two areas, the greater the concentration gradient and the faster the rate of diffusion.
Membrane surface area
The larger the surface area of the membrane that a substance is diffusing through (e.g. the membrane around a cell), the faster the rate of diffusion.
Temperature
The higher the temperature, the faster therate of diffusion
What does partially permeable membrane mean
A partially permeable membrane allows water through, but won’t let larger molecules dissolved in water pass through.
So allows certain substances or molecules
Examples of active transport in real life
Mineral absorbtion in plants
Active transport in the root hairs of plants allows plants to absorb mineral ions, which are necessary for healthy growth, even though the concentration of minerals is usually lower in the soil than in the root hair.
Sugar absorbtion in human gut
Active transport allows sugar molecules, which are needed for cell respiration, to be absorbed into the blood from the gut, even when the sugar concentration of the blood is higher.
Is diffusion active or passive?
Diffusion is a passive process because it doesn’t require any energy from the cell
Explain the role of diffusion in gas exchange?
Oxygen diffuses from the alveoli into the bloodstream
Carbon dioxide diffuses from the bloodstream into the alveoli
What will happen when you put a plant cell in water?
Water wil move into the cell by osmosis and exapand. The cell wall prevents the cell from bursting and instead becomes swollen.
If we place it in a concentrated solution then water moves out by osmosis causing the cell to shrink
What would happen when you place a animal cell in water?
Cytoplasm contains a low concentration of water
So if we place the cell in water, water will move in by osmosis which could cause the cell to expand or even burst
What is a solute?
A substance like salt and sugar which can be dissolves within a solvent like water
So, water travels in osmosis when there is a higher solute concentration and low water concentration
What does hypertonic and hypotonic mean?
Where there is a higher solute concentration is hypertonic
Where there is a low solute concentration is hypotonic
What is isotonic?
Equal concentration
