Bioenergetics

• Photosynthesis is an endothermic reaction as it takes in energy from the environment
• carbon dioxide + water ---> glucose + oxygen
• 6CO2 + 6H2O ----> C6H12O6 +6O2
• Plant uses light for their source of energy
• Photosynthesis takes place in the leaves of a plant
• Chloroplasts are found inside the cells of the leaf, they contain chlorophyll which absorbs sunlight to make photosynthesis happen.
• Glucose is to release energy in respiration
• Photosynthesis only produces glucose during the day, where there is light. The plant cells respire at night and so glucose is stored in starch and at night starch will release glucose
• The glucose can produce amino acids and amino acids are used to synthesise proteins. To make amino acids from glucose, , plants need to absorb nitrate ions from the soil
• Humans and animals need energy to keep warm. We need energy for movement and we need energy for chemical reactions to build larger molecules
• The energy we need is supplied by a process called cellular respiration. Respiration is an exothermic reaction because it releases energy and it continually takes place in living cells
• In aerobic respiration, the sugar glucose is reacted with oxygen gas. This produces carbon dioxide and water and releases energy. Aerobic respiration releases a great deal of energy and this is because the glucose molecule has been fully oxidised
• Anaerobic respiration is in muscles. Muscle cells need a great deal of energy for contraction
• Anaerobic respiration releases less energy than aerobic respiration because in anaerobic respiration , the oxidation of glucose is incomplete
• During exercise, the body needs a great deal of energy for muscle contraction and the body has to react to the increased demand for energy because as the body needs more energy, aerobic respiration increases and this means that the body cells require more oxygen
• To provide more oxygen, both the breathing rate and the breathing volume increases. We breathe more frequently and we take deeper breaths. This gets more oxygen into the bloodstream. The heart rate increases to pump oxygenated blood around the body. Sometimes there is not enough oxygen supplied for the muscles, especially when we exercise hard and so anaerobic respiration takes place in the muscles
• The energy released by respiration is used by enzymes to synthesise new molecules in the cell
• Metabolism is the sum of all the chemical reactions in a cell or the body
• Glucose is a very important reaction in metabolism because it is the main source of energy for cells
• Glucose in plants are converted into cellulose and it strengthens the plant wall. Glucose is a storage for starch. Glucose reacts with nitrate ions to make amino acids and this is used to synthesise proteins
• Glucose in humans is used to make glycogen in the liver and muscles. It is also a storage form of glucose