2.12 Understand definitions of diffusion, osmosis and active transport.
Diffusion: The net movement of molecules from a region of high concentration to a region of lower concentration down a concentration gradient.
Osmosis: The diffusion of water, from a dilute solution into a more concentrated solution through a partially permeable membrane.
Active transport: The movement of ions or molecules in or out of a cell through the cell membrane against a concentration gradient, using energy released during respiration.
Concentration Gradient: The difference between the concentration inside and outside of the cell.
Osmosis: The diffusion of water, from a dilute solution into a more concentrated solution through a partially permeable membrane.
Active transport: The movement of ions or molecules in or out of a cell through the cell membrane against a concentration gradient, using energy released during respiration.
Concentration Gradient: The difference between the concentration inside and outside of the cell.
2.13 Understand that movement of substances into and out of cells can be by
diffusion, osmosis and active transport.
Diffusion: Molecules pass through a partially permeable membrane which only allows small particles through. This is called a passive movement, as they do not require energy.
Osmosis: Only involves water molecules. The tiny holes in the membrane allows water molecules to pass through, but not larger particles. The water moves from a dilute solution with a high concentration of water to a concentrated solution with a low concentration of water.
Active Transport: Cells take up molecules and ions to keep them in high concentration. The cell membrane contains carrier proteins. These proteins span the cell membrane and provide a means by which ions and molecules can enter or leave a cell by active transport. First the molecules or ion combines with the carrier protein. Then energy is used to change the shape of the cell membrane, allowing the molecules to be carried to the inside of the membrane, the carrier protein then returns to it's original shape.
Osmosis: Only involves water molecules. The tiny holes in the membrane allows water molecules to pass through, but not larger particles. The water moves from a dilute solution with a high concentration of water to a concentrated solution with a low concentration of water.
Active Transport: Cells take up molecules and ions to keep them in high concentration. The cell membrane contains carrier proteins. These proteins span the cell membrane and provide a means by which ions and molecules can enter or leave a cell by active transport. First the molecules or ion combines with the carrier protein. Then energy is used to change the shape of the cell membrane, allowing the molecules to be carried to the inside of the membrane, the carrier protein then returns to it's original shape.
2.15 Understand the factors that affect the rate of movement of substances into and out of cells.
Surface area to volume ratio
Larger surface area = Faster rate of movement Smaller surface area = Slower rate of movement This is because a larger surface area, gives molecules more surfaces through which to diffuse, this increases the rate of moment. |
Temperature
Higher temperature = Faster rate of movement Lower temperature = Slower rate of movement This is because the higher the temperature the more kinetic energy. This means that molecules collide with the cell membrane more often making movement through it more likely |
Concentration gradient
Larger concentration gradient = Faster rate of movement Smaller concentration gradient = Slower rate of movement If there is a larger difference, it gives the molecules more opportunity to diffuse. |
2.16 Describe experiments to investigate diffusion and osmosis using living and non-living systems.
Diffusion experiment:
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Osmosis experiment:
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