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Bioenergetics (Photosynthesis (Rate of photosynthesis (Required Practical,…
Bioenergetics
Photosynthesis
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Rate of photosynthesis
Temperature
At low temperatures, the rate of photosynthesis is limited by the number of molecular collisions between enzymes and substrates. At high temperatures, enzymes are denatured.
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Food production
Farmers maintain their plants in greenhouses or poly-tunnels, which allows them to :
- Be grown at the optimum temperature.
- Have burners near their plants to produce CO₂ for optimal growth
- Provide their plants with maximum light
- Farmers do this so they can maximize the useful part of their crop(the yield) or to make their plants grow quickly as possible.
- Farmers and growers must balance these three conditions without making their crops too expensive to sell at a profit.
Required Practical
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Apparatus :
- a beaker
- a test tube
- a measuring cylinder (1 or 10cm3)
- a 10 cm piece of pond weed
- a light source
- a meter ruler
- a stop watch.
Method :
- Set up a test tube rack containing a boiling tube at a distance of 10cm away from the light source
- Fill the boiling tube with the sodium hydrogen carbonate solution.
- Put the piece of pond weed into the boiling tube with the cut end at the top. Gently push the pond weed down with the glass rod.
- Leave the boiling tube for 5minutes.
- Start the stop watch and count the number of bubbles produced in one minute.
- Record the results in a table such as the one here.
- Repeat the count twice more. Then use the data to calculate the mean number of bubbles per minute.
- Repeat steps 1‒7with the test tube rack and boiling tube at distances of 20 cm, 30 cm and 40 cm from the light source.
- Plot a graph of the rate of photosynthesis (given by the no. of bubbles) against light intensity(using the inverse square law)
Variables
- Independent variable – distance from the light source/light intensity.
- Dependent variable – the number of bubbles produced per minute.
- Control variables – concentration of water, temperature, using the same piece of pondweed each time.
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Respiration(Exothermic)
Energy is used:
- To drive the chemical reactions needed to keep organisms alive
- Movement ( in animals, energy is needed to make muscles contract, while in plants, it is needed for transport of substances in the phloem)
- For cell division
- To maintain constant conditions in cells and body.(Homeostasis)
- To move molecules against concentration gradient in active transport
- For the transmission of nerve impulses
Aerobic Respiration
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The first stages of respiration occur in the cytoplasm of cells, but most of the energy released is in the mitochondria.
Anaerobic Respiration
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Response to exercise
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Lungs: the rate and depth of breathing increases.
Heart: the heart rate increases.
Arteries: the arteries supplying the muscles with blood dilate
Muscles: the glycogen stored in the muscles is converted back into glucose
Pulse rate: High
- Muscles needs energy to contract. While exercising, the muscles need additional energy as:
- the breathing rate and volume of each breath increases to bring more oxygen into the body and remove the carbon dioxide produced
- the heart rate increases, to supply the muscles with extra oxygen and remove the carbon dioxide produced
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Metabolism
Is the sum of all the chemical reactions that happen in a cell or in your body.
It is regulated by your thyroid gland.
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- The lactic acid that builds up during anaerobic respiration diffuses from a high conc in your muscles cells to a low conc in your blood.
- By the time it reaches your liver it is at a high conc in your blood and so diffuses again into the low conc in your liver.
- Here it is converted back into glucose by an oxidation reaction.
- This then diffuses into the blood for use in either aerobic or anaerobic respiration.
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