Chapter Note: Movement in and out of cells | Biology for GCSE/IGCSE - Year 11 PDF Download

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Movement in and out of cells
? Diffusion
? The net movement of molecules and ions from a region of their higher concentration to a
region of their lower concentration down the concentration gradient, as a result of their
random movement
? The difference in concentrations is known as the concentration gradient
? List 3 examples of diffusion in living organisms
? Respiration
? Photosynthesis
? Products of digestion
? Respiration
? Gas exchanges for respiration in animals and plants, cell membranes are freely permeable
to CO2 and so these diffuse easily in and out of cells.
? Photosynthesis
? Plants need CO2 for photosynthesis which diffuses from the air into the leaves, through
the stomata. It does this because there is lower concentration outside the leaf. CO2
molecules therefore diffuse into the leaf, down this concentration gradient
? Products of digestion
? Products of digestion are absorbed from ileum of mammals by diffusion and flowering
plants use diffusion to attract pollinators like bees and wasps
? Osmosis
? A process by which water molecules pass through a semipermeable membrane from a
higher water potential to a lower water potential
? Osmosis in plants
? H2O diffuses into the cytoplasm and vacuole through the partially permeable membrane.
The cell swells and becomes firm
? Water diffuses out of the cytoplasm and vacuoles through the partially permeable cell
membrane. First, the cell shrinks slightly and becomes flaccid. THen the cell membrane
pulls away from the cell wall, and the cell in plasmolysed
? Active transport
? The movement of molecules and ions in or out of a cell through the cell membrane against a
concentration gradient, using energy from respiration
Page 2


Movement in and out of cells
? Diffusion
? The net movement of molecules and ions from a region of their higher concentration to a
region of their lower concentration down the concentration gradient, as a result of their
random movement
? The difference in concentrations is known as the concentration gradient
? List 3 examples of diffusion in living organisms
? Respiration
? Photosynthesis
? Products of digestion
? Respiration
? Gas exchanges for respiration in animals and plants, cell membranes are freely permeable
to CO2 and so these diffuse easily in and out of cells.
? Photosynthesis
? Plants need CO2 for photosynthesis which diffuses from the air into the leaves, through
the stomata. It does this because there is lower concentration outside the leaf. CO2
molecules therefore diffuse into the leaf, down this concentration gradient
? Products of digestion
? Products of digestion are absorbed from ileum of mammals by diffusion and flowering
plants use diffusion to attract pollinators like bees and wasps
? Osmosis
? A process by which water molecules pass through a semipermeable membrane from a
higher water potential to a lower water potential
? Osmosis in plants
? H2O diffuses into the cytoplasm and vacuole through the partially permeable membrane.
The cell swells and becomes firm
? Water diffuses out of the cytoplasm and vacuoles through the partially permeable cell
membrane. First, the cell shrinks slightly and becomes flaccid. THen the cell membrane
pulls away from the cell wall, and the cell in plasmolysed
? Active transport
? The movement of molecules and ions in or out of a cell through the cell membrane against a
concentration gradient, using energy from respiration
? Human active transport
? Small intestine ? glucose can be actively transported from the lumen of the intestine into
the cells of the villi
? In kidney tubules ? glucose is actively transported out of the tribule and into the blood
? Plants active transport
? Root hair cells ? take in nitrate ions from the cells by active transport
? In the cell membrane of root hair cells are special transport proteins. These proteins pick
up nitrate ions from outside the cell and then change shape which pushes the nitrate ions
through the cell membrane and into the cytoplasm of the cell
Factors affecting rate of diffusion
? Surface area to reduce volume ratio
? The surface area of the second cell is much bigger than the first cell due to the folded
membrane. THe volume of the cells has a much larger surface area to volume ratio and it
increases the rate of diffusion
? Therefore parts of organisms that rely on diffusion have a larger surface area
? Temperature
? At higher temperature the particles have more kinetic energy and are moving around
faster. Therefore in a given time more diffusion will occur
? Concentration gradient
? When there is a big difference between the number of particles in one place than another,
diffusion will happen much faster then if they are already quite spread out