Movement Of Substances

Read all the questions carefully and answer True/T or False/F 1. The larger the volume of a cell or organism, the smaller the surface area across which absorption of useful substances and removal of waste products can take place. 2. The surface area to volume ratio limits the size to which cells can grow. 3. Substances will diffuse down a concentration gradient to regions which have less of them. 4. Osmosis is a passive mechanism which does not require energy expenditure on the part of the cell. 5. Osmosis is a special kind of diffusion. It involves the movement of water molecules from a region of higher water potential to a region of lower water potential through a selectively permeable membrane down a water potential gradient. 6. The plasma membrane is a selectively permeable membrane which allows certain substances to pass through it while preventing others from doing so. 7. The cell wall surrounding plant cells prevents the cells from bursting when they are immersed in a solution of low water potential. 8. Larger animals tend to have more complex systems to provide for the needs of the body because diffusion alone is insufficient to supply their needs. 9. Diffusion occurs at a slower rate when the temperature is high. 10. Diffusion occurs at a faster rate when the concentration gradient is steep. 11. Red blood cells in a hypotonic solution become swollen initially. 12. A plasmolysed cell can be restored to its original state by placing it in water or in a solution with high water potential. 13. An animal cell will crenate when placed in a solution of low water potential. 14. The daily opening and closing of flowers of certain plants is due to turgor. 15. A more dilute solution has lower water potential than another solution. 16. Solutions of the same concentration have the same water potential.

17. The cell walls of plants are semi permeable and allow only some dissolved substances to pass through. 18. Much fertilizer must first be placed around the roots of a wilting plant to ensure its survival. 19. The greater the area of cell surface membrane per unit volume, the faster the rate of diffusion of a substance for a given concentration gradient. 20. A small cell has a larger surface area to volume ratio than a large cell of the same shape. 21. Active transport occurs ONLY in living cells because living cells respire. 22. Active transport requires a semi permeable membrane. 23. Osmosis is a form of active transport as it involves a semi permeable membrane. 24. Active transport is used by root hair cells as well as cells of the human intestines. 25. When a root hair cell is immersed in a hypertonic solution, it uses active transport to keep itself turgid. 26. Concentration gradients provide the energy for diffusion and osmosis to take place. 27. All substances can diffuse across the plasma membrane as long as a concentration gradient is present. 28. Diffusion can occur only when there is solvent and a solute. 29. Diffusion describes the movement of the solute molecules only. 30. Osmosis can occur only when water is in the liquid state. 31. Osmosis can occur only in living organisms. 32. Osmosis will take place wherever there is water potential gradient as long as there is a barrier or membrane which is permeable to water and not to the solute. 33. Active transport is carried out only on those substances which cannot pass through the membrane. 34. The movement of substances against a concentration gradient is an indication that active transport is taking place. Sec 3E Biology 09

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Mr. Lim KS

35. Liver cells have more mitochondria than cheek cells. This implies more active transport takes place in them than the cheek cells.

Sec 3E Biology 09

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Mr. Lim KS