Section 2: d) Movement of substances into and out of cells Flashcards
What is diffusion?
The net movement of particles from a region of their higher concentration to a region of their lower concentration.
What is osmosis?
The net movement of water molecules across a partially permeable membrane from their higher concentration (a dilute solution) to their lower concentration (a more concentrated solution).
What is active transport?
The transfer of molecules across a cell membrane, against a concentration gradient, using energy from cell respiration.
What is net movement?
Where there are more particles moving in one direction than another.
What is a concentration gradient?
A difference in concentration on either side of the membrane.
What type of process are diffusion and osmosis?
Passive
What does passive mean?
Happening without the need for additional energy.
How does surface area affect the rate of movement of substances into and out of cells?
The greater the area of membrane across which the particles can move, the more that will cross in a given time. So the larger the surface area, the faster the rate of diffusion and osmosis.
How does the surface area to volume ratio affect the rate of movement of substances into and out of cells?
The greater the surface area to volume ratio, the faster the rate of diffusion (e.g. with cubes of volume 1cm^3, 8cm^3, 27cm^3 and 64cm^3, 1 cm^3 has highest SA:V ratio and hence fastest rate of diffusion or osmosis).
How does distance affect the rate of movement of substances into and out of cells?
The greater the distance particles have to move (e.g. if there are several membranes to pass through), the longer it takes. So the greater the distance, the slower the rate of diffusion or osmosis.
How does temperature affect the rate of movement of substances into and out of cells?
At a higher temperature, particles have more energy so they move around faster. This means they are more likely to bump into the cell membrane and pass through to the other side. So the higher the temperature, the faster the rate of diffusion or osmosis.
How does the concentration gradient affect the rate of movement of substances into and out of cells?
The greater the difference in concentration on either side of a cell membrane, the more particles will move from the concentrated side to the less concentrated side. So the greater the concentration gradient, the faster the rate of diffusion or osmosis.
What happens to the surface area to volume ratio as the size increases?
As the size increases, the surface area to volume ratio decreases.
