Bioenergetics

Bioenergetics

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Photosynthesis

Photosynthesis is the process in which the raw materials water and carbon dioxide are used to make glucose. Oxygen is produced as a by-product. It takes place within the chloroplasts within the leaf. Chlorophyll is found here which is used to absorb light energy. This is an endothermic process. Equation: 6CO2 + H2O -> C6H12O6 + O2Carbon dioxide + Water -> Glucose + Oxygen

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Caption: : The chloroplasts are in the palisade cells

Limiting Factors

A limiting factor of photosynthesis is a factor that is stopping the process of photosynthesis from taking place faster The limiting factors of photosynthesis are light, concentration of CO2 and temperature All of these factors have an overall effect upon the rate of photosynthesis. The environmental conditions determine which factor is limiting At night it is light In winter it is temperature If it is warm and bright enough then concentration of CO2 may be the limiting factor Chlorophyll can also be a limiting factor. Amount of chlorophyll can be affected by disease (e.g. tobacco mosaic virus) or lack of nutrients.  These factors can cause chloroplasts to become damaged or not be able to produce enough chlorophyll The rate of photosynthesis is therefore reduced as not as much light can be harnessed

Rate of Photosynthesis: Light

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Light provides the energy that is required for the process of photosynthesis When light intensity is a limiting factor and light level is raised then the rate of photosynthesis increases steadily but up to a point From this point onward either temperature of carbon dioxide concentration will be limiting A light meter is used to get accurate results of light intensity

Caption: : Rate of photosynthesis against light intensity

Rate of Photosynthesis: Carbon Dioxide

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Caption: : Rate of photosynthesis against carbon dioxide concentration

Carbon dioxide is one of the raw material needed for photosynthesis The graph is similar to the light intensity graph because it is only the limiting factor up to a point From that point onward the line flattens out as it is no longer the limiting factor If light and carbon dioxide concentration are in perfect supply then temperature may be the limiting factor

Rate of Photosynthesis: Temperature

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Caption: : Rate of photosynthesis against temperature. The optimum temperature is located where the peak of the line is

Temperature is normally a limiting factor if it is too low Enzymes (biological catalysts) are used in photosynthesis for various chemical reactions Enzymes work slowly at lower temperatures but work very well at optimum temperatures If the plant gets too hot however, the enzymes needed for photosynthesis and other reactions will be damaged and start to denature If an enzyme is denatured then the shape of the active site will change which will cause the enzyme to slowly stop working 45*C is often the temperature at which this happens

Required Practical: Photosynthesis

Canadian pond-weed can be used to measure the effect of light intensity upon the rate of photosynthesis. The rate at which oxygen is produced corresponds to the rate of photosynthesis. A lamp is placed at a specific distance from the pond-weed The pond-weed is left to photosynthesise for a set amount of time. The oxygen released will collect in the capillary tubing The syringe is used after the experiment to draw the gas in the tube up along the ruler to measure the length of the gas bubble. This is proportional to the volume of O2 produced This experiment is repeated at different distances away from the pond-weed Variables to be controlled: temperature, time pond-weed is left_______________________________________________________________________________This experiment can be used to test the effect of temperature using a water bath of different temperaturesThis experiment can also be used to test effect of carbon dioxide using different concentrations of sodium hydrogen carbonate dissolved in the water (it releases carbon dioxide)

Required Practical: Diagram

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Caption: : The Experiment

The Rate of Photosynthesis: The Law

When the lamp is moved away from the pond-weed the amount of light that reaches it decreases As distance increases light intensity decreases. This is an inversely proportional relationship The light intensity decreases in proportion to the square of the distance which is known as the inverse square law:The EquationLight intensity ∝ 1 / distance (d)^2This law shows that if you halve the distance the light intensity is four times greater. If you treble the distance then the light intensity will be nine times smaller.

Greenhouses

Greenhouses are used to artificially create an ideal environment for plants to grow Greenhouses trap the sun's heat to ensure that temperature is not a limiting factor In Winter a heater may be used to keep the temperatures at the ideal level If it gets too hot then shades or ventilation may be used to cool the greenhouse down Light is often supplied after the sun goes down at night to allow plants to photosynthesise for longer Carbon dioxide levels are also regulated by farmers. Paraffin heaters heat the greenhouse as well as give off carbon dioxide as a by-product Plants are kept away from pests and disease by keeping them enclosed within the greenhouse. Fertilisers are also used to ensure that the plants are able to get all the minerals they need from the soil Money is needed for all of this. However, if the farmer is able to keep the conditions at the optimum level (no extra costs) then a decent from can be grown faster and can be harvested more often. An excess of light or carbon dioxide will be wasting money so the farmers need to be aware of this.

A Greenhouse

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Uses of Glucose

Glucose is used by plants in five different ways: Respiration - Energy is trasferred from the glucose  to enable the plant to carry out different processes such as converting the glucose into various substances Making Cellulose - Glucose is converted into cellulose to make strong cell walls Making Amino Acids - Glucose is combined with nitrate ions from the soil to make amino acids, which are then made into proteins Stored as oils / Fats - Glucose is tuned into lipids (fats and oils) for storing in seeds Stored as Starch - Glucose is converted into starch in order to store it in roots, stems and leaves. This is so that it is ready to use when photosynthesis is not happening such as in winter.  Starch is insoluble and so it is easier to store than glucose. A cell with lots of glucose would swell up as it is soluble in water.

Respiration

Respiration is the process of transferring energy from the breakdown of glucose. All living things (including plants) respire. Living things transfer energy from their food to every single cell in the body. Respiration is an exothermic reaction as it transfers energy to the environment Organisms use energy from respiration in different ways. In mammals, it is used for keeping body temperatures steady and allow muscles to contract. Another use of the energy is to build up larger molecules (e.g. proteins from amino acids)

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Caption: : The respiration equation

Aerobic and Anaerobic Respiration

Metabolism

There are many chemical reactions within cells which are happening all the time. These are controlled by enzymes Many of these reactions are liked to form bigger reactions In some reactions smaller molecules of glucose are joined to form starch Lipid molecules are made from one molecule of glycerol and three fatty acids Glucose is combined with nitrate ions to make amino acids which are then made into proteins In some reactions larger molecules are broken down into smaller molecules Glucose is broken down to release energy which powers other reactions Excess protein is broken down to produce urea which is excreted through unimn

Aerobic and Anaerobic Respiration

Exercise