Additional Science Chapter 3 Energy Release Every cell needs energy to keep it alive. This energy comes from glucose. This sugar is broken down by a series of reactions called respiration. These reactions are speeded up by enzymes acting as biological catalysts.
Additional Science Chapter 3 Aerobic respiration This is the usual type of respiration seen in humans - it uses oxygen. The reactions of respiration take place in tiny structures called mitochondria (singular: mitochondrion) and they are referred to as the ‘power-houses’ of the cell because they produce the cell’s energy. Mitochondrion
Additional Science Chapter 3 Anaerobic Respiration Respiration can happen without oxygen. This process is called anaerobic respiration. Only a portion of the energy contained in the glucose is released. Higher
Additional Science Chapter 3 Anaerobic respiration in yeast cells When yeast respires without the presence of oxygen (anaerobic respiration) it produces ethanol (alcohol). This process is called fermentation. Glucose CO 2 + ethanol+H 2 O +EGNI Higher
Additional Science Chapter 3 Anaerobic respiration in the muscles When muscles work hard and the oxygen level decreases in the cells, they can respire anaerobically for a short time to enable them to keep going: glucose lactic acid + energy Higher
Additional Science Chapter 3 Disadvantages of Anaerobic Respiration It doesn’t release all the energy trapped in the glucose. Ethanol is toxic to cells. Lactic acid builds up in muscle cells and causes cramp. Higher
Additional Science Chapter 3 Oxygen Debt During physical exercise, acid lactic builds up in the muscles and it needs to be broken down. The body needs oxygen to do this and so we breathe deeper and quicker. In a way, we are paying this oxygen back. The name given to the ‘loan’ is oxygen debt. Higher O2O2 O2O2
Additional Science Chapter 3 Practical Work Energy release from respiring seeds. The peas in the three flasks below have been treated differently:
Additional Science Chapter 3 Flasks of peas A BC thermos flask metal case fresh pea seedsboiled pea seedsboiled pea seeds in disinfectant temperature probes datalogging interface computer time temperature clock A computer can be used to prove that respiring peas release energy in the form of heat.
Additional Science Chapter 3 Results fresh pea seeds boiled pea seeds boiled pea seeds in disinfectant
Additional Science Chapter 3 Question Why do the boiled peas that haven’t been disinfected cause a temperature increase?