Movement in and out of cells
Movement in and out of cells
Diffusion:
(mixing molecules)
Molecules and ions in a liquid or a gas move continuously. The movement is quite random, and the particles change direction as they bump into one another. The particles collide more often when they are close together (when they are concentrated) and so they tend to diffuse, or spread out, until they are spaced evenly throughout the gas or liquid. The random movement of particles is due to their own kinetic energy. When the diffusion happens in living cells, the cells themselves do not have to expend any energy for it to take place.
What 4 things can we define diffusion as?
The net movement of molecules within a gas or liquid.
From a region of high concentration to a lower region
As a result of their random movement
Until an equilibrium is reached.
What are partial permeable membranes?
Not all particles can diffuse through cell surface membranes. Sometimes the particles are too big or they have the wrong electrical charge on them or the chemical composition of the membrane prevents them passing across.
What does a diagram of a partially permeable membrane look like when it is permeable to glucose and water but impermeable to protein?
What living organisms have certain adaptations to speed up diffusion?
Diffusion distances are short – the membranes in the lungs, for example, are very thin so that the oxygen and carbon dioxide can diffuse between the blood and the lung air spaces.
Concentration gradients are maintained – glucose molecules that cross from the gut into the blood, for example, are quickly removed by circulating blood so that their concentration does not build up and equilibrium is not reached.
Diffusion surfaces are large – the surface of the placenta, for example, is highly folded to increase the surface area for the diffusion of molecules between a pregnant female and the developing fetus in her uterus.
Diffusion:
(mixing molecules)
Molecules and ions in a liquid or a gas move continuously. The movement is quite random, and the particles change direction as they bump into one another. The particles collide more often when they are close together (when they are concentrated) and so they tend to diffuse, or spread out, until they are spaced evenly throughout the gas or liquid. The random movement of particles is due to their own kinetic energy. When the diffusion happens in living cells, the cells themselves do not have to expend any energy for it to take place.
What 4 things can we define diffusion as?
The net movement of molecules within a gas or liquid.
From a region of high concentration to a lower region
As a result of their random movement
Until an equilibrium is reached.
What are partial permeable membranes?
Not all particles can diffuse through cell surface membranes. Sometimes the particles are too big or they have the wrong electrical charge on them or the chemical composition of the membrane prevents them passing across.
What does a diagram of a partially permeable membrane look like when it is permeable to glucose and water but impermeable to protein?
What living organisms have certain adaptations to speed up diffusion?
Diffusion distances are short – the membranes in the lungs, for example, are very thin so that the oxygen and carbon dioxide can diffuse between the blood and the lung air spaces.
Concentration gradients are maintained – glucose molecules that cross from the gut into the blood, for example, are quickly removed by circulating blood so that their concentration does not build up and equilibrium is not reached.
Diffusion surfaces are large – the surface of the placenta, for example, is highly folded to increase the surface area for the diffusion of molecules between a pregnant female and the developing fetus in her uterus.