National 5 Respiration Mr G Davidson

Energy in Food Food is a source of energy for all organisms. This energy is measured in Joules (J) or kilojoules (kJ). (1000J = 1kJ) We can measure the amount of energy in a foodstuff by using it as an energy source to heat a known volume of water and measuring the rise in temperature. Tuesday, September 18, 2018 Mr G Davidson

Energy in Food Thermometer We need to know the starting temperature of the water and the finishing temperature of the water. This allows us to calculate the rise in temperature. We also need to know the mass of the food we are burning. Known volume of water Burning Food Tuesday, September 18, 2018 Mr G Davidson

Energy in Food Once we have carried out the experiment, we should be able to fit the results into the following equation. M= mass of water (g) T= rise in temperature (oC) Energy (kJ) = 4.2 x M x T 1000 Tuesday, September 18, 2018 Mr G Davidson

Energy in Food The 4.2 comes from:- it takes 4.2 kJ to raise 1kg of water by 1oC, e.g. If using a peanut weighing 2g to heat 50g water from 20oC to 58oC, we would enter the following. M=50 T= 58-20= 38 So: 4.2 x 50 x 38 = 7.98 1000 Tuesday, September 18, 2018 Mr G Davidson

Energy in Food We must remember that this number is for 2g of peanut. Therefore, if 2g releases 7.98kJ of energy, then 1g of peanut releases 3.99kJ of energy. These figures can be worked out more accurately using a food calorimeter. The energy values are often displayed on the side of food packets. Tuesday, September 18, 2018 Mr G Davidson

Respiration Respiration is the chemical process in cells which releases energy from food. Glucose is the main source of energy in cells and releases 17kJ per gram. During respiration, glucose is broken down by enzymes in a series of biochemical reactions. Tuesday, September 18, 2018 Mr G Davidson

Respiration During this process energy is released. Some of this energy is transferred to other chemicals and some of this energy is lost as heat. In some organisms, this heat energy is essential if the organism is to maintain a constant temperature. Tuesday, September 18, 2018 Mr G Davidson

Adenosine Tri-phosphate (ATP) An adenosine tri-phosphate molecule consists of adenosine attached to three inorganic phosphate molecules. Pi Pi Pi ADENOSINE Tuesday, September 18, 2018 Mr G Davidson

Adenosine Tri-phosphate (ATP) ATP is made using adenosine diphosphate (ADP), which contains two inorganic phosphates, and adding another inorganic phosphate. ADENOSINE Pi Pi Adenosine diphosphate Inorganic phosphate Tuesday, September 18, 2018 Mr G Davidson

ATP When the energy is released from glucose, some of it is used to join the inorganic phosphate to the ADP to make ATP. High energy bond ADENOSINE Pi Pi Inorganic phosphate Adenosine diphosphate Tuesday, September 18, 2018 Mr G Davidson

ATP The energy used to join the phosphate to the ADP is stored in a high energy bond. This energy is now available for a quick release as and when the cell needs it. The high energy bond is broken and the stored energy is released. Tuesday, September 18, 2018 Mr G Davidson

ATP When energy once again becomes available to the cell the ADP and P are put back together to make ATP. This build up of ATP is called PHOSPHORYLATION. Energy released ATP ADP + Pi Energy used up High energy compound Low energy compound Tuesday, September 18, 2018 Mr G Davidson

Chemistry of Respiration Respiration is the process which releases chemical energy from glucose. Respiration occurs in ALL living cells. When there is an ample supply of oxygen it is called aerobic respiration. Respiration builds up ATP molecules. Aerobic respiration occurs in the mitochondria of the cell. Tuesday, September 18, 2018 Mr G Davidson

Respiration A 6-carbon glucose molecule is broken down by a series of enzyme controlled reactions into two 3-carbon molecules of pyruvate (pyruvic acid). This process is called glycolysis and does not require oxygen. It occurs in the cytoplasm. It also releases enough energy to regenerate 2 molecules of ATP. Tuesday, September 18, 2018 Mr G Davidson

Glycolysis Pyruvate Glucose Pyruvate 2 ADP + Pi 2 ATP Tuesday, September 18, 2018 Mr G Davidson

Chemistry of Respiration Pyruvate still contains a lot of energy and is now broken down even further by enzymes in the presence of oxygen. This occurs in the mitochondria. This stage requires oxygen. Each pyruvate is broken down to carbon dioxide and water, and this releases enough energy to make 18 molecules of ATP. Tuesday, September 18, 2018 Mr G Davidson

Chemistry of Respiration This means a total of 36 ATP molecules are produced from the two pyruvic acid molecules. If this is added to the 2 molecules of ATP produced in glycolysis it means that one molecules of glucose can release enough energy to regenerate a total of 38 ATP molecules. Tuesday, September 18, 2018 Mr G Davidson

Chemistry of Respiration 18ADP + Pi 18ATP Carbon dioxide + Water Pyruvic acid Glucose 2 ADP + Pi + OXYGEN 2 ATP Carbon dioxide + Water 18ADP + Pi 18ATP Tuesday, September 18, 2018 Mr G Davidson

Anaerobic Respiration Anaerobic respiration occurs when there is no oxygen. It involves the partial breakdown of glucose. Glycolysis occurs as normal, releasing its 2 ATP molecules. Tuesday, September 18, 2018 Mr G Davidson

Anaerobic Respiration However, the pyruvate is converted to other molecules depending on whether the organism is a plant or an animal. In animals pyruvate is converted into lactic acid. Tuesday, September 18, 2018 Mr G Davidson

Anaerobic Respiration This lactic acid can be converted back to pyruvic acid when oxygen becomes available. Lactic acid results in muscle fatigue which reduces the efficiency of the muscle cells, and eventually leads to cramp. Tuesday, September 18, 2018 Mr G Davidson

Anaerobic Respiration During periods of anaerobic respiration an oxygen debt builds up, and this oxygen must be repaid to convert the lactic acid back to pyruvic acid. This makes anaerobic respiration in animals a reversible process. Tuesday, September 18, 2018 Mr G Davidson

Anaerobic Respiration in Animals Glucose 2 ADP + Pi 2 ATP Pyruvate Recovery period Vigorous exercise + OXYGEN Lactic acid Tuesday, September 18, 2018 Mr G Davidson

Anaerobic Respiration in Plants Anaerobic respiration in plants and yeast results in pyruvate being converted to ethanol and carbon dioxide. This process is known as fermentation. The carbon dioxide is released as a waste product, and this makes anaerobic respiration in plants an irreversible process. Tuesday, September 18, 2018 Mr G Davidson

Anaerobic Respiration in Plants Glucose 2 ADP + Pi 2 ATP Pyruvate Ethanol + Carbon dioxide Tuesday, September 18, 2018 Mr G Davidson