Bionergetics - topic 4 (paper 1)

• Cellular respiration is an exothermic reaction which is continuously occurring in living cells.
• Inverse proportion is a relationship between two values where as one value increases, the other value decreases at the same rate.
• Limiting factor is a factor that limits the rate of a reaction when there is not enough of it.
• Metabolism is the sum of all the reactions in a cell or the body.
• Oxygen debt is the amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells.
• Urea forming from the breakdown of proteins for excretion
• Photosynthesis is an endothermic reaction in which energy is transferred from the environment to the chloroplasts by light.
• Photosynthesis is the process by which plants make glucose from sunlight, an endothermic reaction in which energy is transferred from the environment to the chloroplasts by light.
• The equation for photosynthesis is: light carbon dioxide + water → glucose + oxygen.
• Each compound in photosynthesis has its own chemical symbol: Carbon dioxide: CO 2 Water: H 2 O Oxygen: O 2 Glucose: C 6 H 12 O 6.
• The rate of photosynthesis is affected by temperature, light intensity, carbon dioxide concentration, and the amount of chlorophyll.
• With an increase in temperature, the rate of photosynthesis increases, as the reaction is controlled by enzymes, this trend continues up to a certain temperature until the enzymes begin to denature and the rate of reaction decreases.
• For most plants, the higher the light intensity, the faster the rate of the reaction.
• Carbon dioxide is also needed to make glucose, as the concentration of carbon dioxide increases, the rate of reaction increases.
• Chlorophyll is a pigment in the leaf that converts light energy to food for the plant, and is therefore essential, if chlorophyll levels are reduced through a magnesium deficiency, then the rate of photosynthesis would decrease.
• The rate of photosynthesis can be measured by carrying out an experiment measuring the oxygen production of a plant, this involves placing pondweed in a test tube full with water, sealing the top with a bung, attaching a capillary tube containing water to a syringe, placing a lamp at a measured distance from the test tube, and measuring the distance the bubble has moved to calculate the volume of oxygen produced.
• If there is not enough oxygen being supplied, anaerobic respiration takes place instead, with lactic acid as a byproduct, this reaction builds up creating an oxygen debt as oxygen is needed to break lactic acid down.
• Farmers can use the knowledge of limiting factors to enhance the conditions in the greenhouse for a greater rate of photosynthesis, leading to increased growth and profits.
• Respiration can take place aerobically (with oxygen) or anaerobically (without oxygen).
• Metabolism is the sum of all the reactions in a cell or the body, the energy transferred in the cells by respiration is used in the processes of metabolism to make new molecules.
• Inverse proportion describes a relationship between two factors which involves one increasing whilst one decreasing, as the distance between the light source and the plant increases, the light intensity decreases.
• Respiration is exothermic as energy is transferred to the environment.
• Examples of metabolic reactions include glucose molecules being converted to starch, glycogen and cellulose by being joined together, a glycerol molecule and three molecules of fatty acids forming a lipid molecule, glucose and nitrate ions forming amino acids, which are used to form proteins, and the reactions in respiration.
• The light intensity is inversely proportional to the square of the distance, known as the inverse square law.
• If a lamp is 2 metres away from a plant, then the light intensity of the lamp is a ¼ of its original value.
• The oxidation of glucose is complete in animals, with glucose converting to lactic acid.
• Glucose from photosynthesis is used for respiration, converted into insoluble starch for storage in roots, stems and leaves, used to produce fat or oil for storage in seeds, used to produce cellulose to strengthen cell walls, and combined with nitrates (absorbed from the soil) to form amino acids which produce proteins.
• During exercise, more energy is needed for the muscles to contract, meaning respiration has to occur faster, and more oxygen needs to be supplied to cells (and more CO2 removed).
• Blood flowing through the muscles transports the lactic acid to the liver where it is converted back to glucose.
• Aerobic respiration uses oxygen and yields the most energy, with most of the reactions that make up aerobic respiration occurring in the mitochondria.
• In plant and yeast cells, the oxidation of glucose is incomplete, with glucose converting to ethanol and carbon dioxide, this reaction is used to make bread and alcoholic drinks.
• A graph involving three limiting factors includes temperature, light intensity, and carbon dioxide, with temperature as the limiting factor.
• Anaerobic respiration does not use oxygen and yields less energy, it is only used as a last resort, for example during a sprint where it is difficult to breathe in enough oxygen.
• Respiration occurs in every cell in the body, and it is the process of transferring energy from glucose so living processes can occur.
• Many variables can be changed to observe their effect on photosynthesis: temperature, time, light intensity, carbon dioxide concentration, and the amount of chlorophyll.
• A limiting factor in photosynthesis is an environmental condition which, in low levels, restricts any increase in the rate of photosynthesis.
• A graph involves one limiting factor if it has one line which levels off, with the factor on the horizontal axis and rate of photosynthesis on the vertical axis.
• A graph with two lines represents two limiting factors in two experiments, the investigation involves increasing the factor on the horizontal axis, and is carried out at two different other environmental conditions, such as two different temperatures.
• Light intensity is measured in lux and in a graph with two lines, the limiting factor is light intensity.