Respiratory physiology

Biology B3 B3.1 Exchange of materials 1.1 Osmosis Osmosis is the net movement of water particles from an area of high water concentration to an area of low water concentration across a partially permeable membrane (e.g. a cell membrane) It?s random and re quires no energy 1.2 Active transport Cells may need to absorb substances which are in short supply, i.e. against the concentration gradient. To do this they use active transport to absorb substances across partially permeable membranes Active transport requires the use of energy released in respiration Cells are able to absorb ions from dilute solutions. For example, root cells absorb mineral ions from the dilute solutions in the soil by active transport Glucose can be reabsorbed in the kidney tubules by active transport