03. Movement In and Out of Cells

• Define diffusion as the net movement of particles from a region of their higher concentration to a region of their lower concentration down a concentration gradient, as a result of their random movement

• Describe the importance of diffusion of gases and solutes

• State that substances move into and out of cells by diffusion through the cell membrane

• State that the energy for diffusion comes from the kinetic energy of random movement of molecules and ions

• Investigate the factors that influence diffusion, limited to surface area, temperature, concentration gradients and distance

• State that water diffuses through partially permeable membranes by osmosis

• State that water moves in and out of cells by osmosis through the cell membrane

• Investigate and describe the effects on plant tissues of immersing them in solutions of different concentrations

• State that plants are supported by the pressure of water inside the cells pressing outwards on the cell wall

• Define osmosis as the net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution), through a partially permeable membrane

• Explain the effects on plant tissues of immersing them in solutions of different concentrations by using the terms turgid, turgor pressure, plasmolysis and flaccid

• Explain the importance of water potential and osmosis in the uptake of water by plants

• Explain the importance of water potential and osmosis on animal cells and tissues

• Explain how plants are supported by the turgor pressure within cells, in terms of water pressure acting against an inelastic cell wall

• Define active transport as the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration

• Discuss the importance of active transport as a process for movement across membranes:

– e.g. ion uptake by root hairs and uptake of glucose by epithelial cells of villi and kidney tubules

• Explain how protein molecules move particles across a membrane during active transport