Bioenergetics

Takes place in chloroplasts in green plant cells which contain pigmants like chlorophyll that absorb light. Ebergy is transferred to the chloroplasts from the enviroment by light. Photosynthesis is endothermic as it takes in energy.

Carbon Dioxide + Water (+ Light) -> Glucose + Oxygen

6CO2 + 6H2O -> C6H12O6 + 6O2

Glucose is used in 5 main ways:

• Respiration - transfers energy from glucose which enables the plant to convert it into other usefull substances.
• Making cellulose - used for strong plant cell walls.
• Making amino acids - combined with nitrate ions from the soil to make amino acid, which are then used for proteins,
• Stored as oils or fats - turned into lipids for storing in seeds.
• Stored at starch - turned into startch and stored in the roots, stems and leaves, ready for use when photosynthesis isnt happening. Starch in insolubleand so does not draw iin lots of water.

Limiting factors - light intensity, concentration of CO2 and temperature. At night, light will be the limiting factor and in winter it will likely be temperature or CO2. Chloropyll will be the limiting factor if the plant has a disease or undergoing enviromental stress, such as lack of nutrients, causing the chloroplasts to become damaged.

Pratical:

• Place a source of white light at a specific distance from pondweed within a test-tube filled with water attached to a capillary tube and syringe and ruler.
• leave the pondweed to photosynthesise for a set amount of time.
• The syringe ise used to draw the gass bubbles in the tube along the ruler and the length is measured, this is proprtional to the amount of O2 produced.
• Repeat with the light source at different distances from the pondweed.

As the distance increases, the light intensity decreases. The light intensity is inversely proportional to the square of the distance: LI = 1/d^2.

Greenhouses:

• Trap the sun's heat so temperature does not become a limiting factor. May use a heater or ventilation to create ideal conditions.
• Supply artificial light to give plants more time to photosynthesis.
• Increase the level of photosynthesis,e.g. by using a paraffin heater which release CO2 as a by-product.
• Keeps plants enclosed and away from pests or diseases. May use fertilisers to provide more minerals

Respiration is the process of transferring energy energy from the breakdown of glucose (sugars) and it goes on in every cell in your body continuously. All things respire. Respiration is exothermic as it transfers energy to the surroundings.

Three main uses of respiration:

• To build up larger molecules from smaller ones (like proteins from amino acids).
• In animals its used to allow the muscles to contract.
• In mammals and birds its used to keep body temperature steady in colder suroundings.

Metabolism is all the sum of all the reactions that happen in a cell or the body. These chemical reactions are controlled by enzymes and can join or break down molecules.

• Aerobic - efficient respiration using oxygen. This occurs all the time in plants and animals, usually within the mitochondria of cells.

glucose + oxygen -> carbon dioxide + water

C6H12O6 + 6O2 -> 6CO2 + 6H2O

• Anaerobic - respirationduring exercise when the supply of oxygen needed is too high. It is the incompleate breakdown of glucose, making lactic acid. The glucose is not fully oxidised so does not transfer as much energy, therfore it can only be used in emergencies.

glucose ->lactic acid

• Anaerobic respiration in plants - in yeast cells this is called fermentation and can be used to make bread or alcoholic drinks as it produces the alcohol for beer and wine.

glucose -> ethanol + carbon dioxide

Muscles need more energy rom respiartion to contract more frequently and with greater force. Therefore, your breathing rate and volume increases to get more oxygen into the blood and get it around the body faster, thus removing CO2 more quickly. Intense exercise results in anaerobic respiration hwever the build up of lactic acid can cause this to be painful. Long periods of exercise can cause muscle fatigue - when the muscles do not respire efficiently.

After anaerobic exercise, you have an "oxygen debt" - the amount of extra energy needed to react with the build up of lactic acid and remove it from the cells (forming CO2 and water). This results in heavy breathing and rasied heat-rate after exercise to get more oxygen into the blood. The blood also transports lactic acid from the muscles to the liver where it is converted back to glucose.