Bioenergetics

• • Carbon dioxide + water ---> oxygen + glucose

  6CO2                  + 6H2O         6O2       + C6H12O6
• • When the light intensity is 0, the rate of photosynthesis is 0. Plants need light to carry out photosynthesis. As we increase the light intensity, the rate of photosynthesis increases. The plant now has more light energy to carry out photosynthesis so the reaction gets faster. It is a limiting factor, at one point the rate of photosynthesis does not increase anymore and is just at the same level.
• • As we increase the carbon dioxide level, the rate of photosynthesis increases. It is a limiting factor, at one point the rate of photosynthesis does not increase anymore and is just at the same level.
• • As we increase the temperature, the enzymes involved in photosynthesis work faster so the rate increases. If we keep increasing the temperature, the enzymes will denature and the rate of photosynthesis falls.
• • Glucose produced by photosynthesis is to produce the storage molecule starch. The starch can be converted back to glucose by the plant when it’s needed. Glucose can also be converted to fats and oils which are used by the plant as a storage form of energy.
  • The plant cell is enclosed in a cell wall which contains cellulose that gives the cell its strength. It is made from the glucose produced by photosynthesis. 
  • Glucose can also be used produce amino acids which are used by the plant to synthesise proteins. To make amino acids from glucose, plants need to absorb nitrate ions from the soil.
• • Muscle cells need a great deal of energy for contraction. Under certain conditions, the amount of oxygen is limited. When there is a shortage of oxygen, muscle cells respire anaerobically. 
  • During anaerobic respiration in muscles, glucose is converted to lactic acid. This doesn’t require any oxygen. Anaerobic respiration releases much less energy than aerobic respiration because the oxidation of glucose is incomplete.
  • Anaerobic in plant and yeast cells: glucose ---> ethanol + carbon dioxide
  • Anaerobic respiration in yeast cells is called fermentation
• During exercise the body needs a great deal of energy for muscle contraction. The body has to react to the increased demand for energy. Because the body needs more energy, aerobic respiration increases which means that the body cells require more oxygen. To provide this extra oxygen, both the breathing rate and the breathing volume increase. We breathe more frequently and we take deeper breaths which gets more oxygen into the bloodstream. The heart rate also increases to pump this oxygenated blood around the body.
• Sometimes not enough oxygen can be supplied to the muscles if we are exercising hard. Anaerobic respiration will then take place in the muscles. During long periods of vigorous activity, the lactic acid causes the muscles to become fatigued which causes the muscles to stop contracting efficiently. The body has to remove the lactic acid from the muscles which creates a condition called oxygen debt. The lactic acid is transported out of the muscles by the blood, then taken to the liver and converted back to glucose. Reacting with the lactic acid and removing it from the cells require oxygen.
• The oxygen debt is the amount of extra oxygen the body needs after exercise to deal with the accumulated lactic acid. This is why people continue breathing rapidly for some time after finishing exercise.
• • Metabolism is the sum of all chemical reactions in a cell or the body.