2.37 Describe experiments to investigate the evolution of carbon dioxide and heat from respiring seeds or other suitable living organisms

Experiment would be set up as follows to investigate release of carbon dioxide:

• Put x grams of germinating seeds in a test tube.
• Cover it with a bung/cork with a tube through it
• Have one end of the tube in limewater
• If it turns cloudy, carbon dioxide has been given off
• See figure 1

Figure 1: Apparatus

To investigate the release of heat:

• Put seeds in a test tube
• Seal it with a cotton puff
• Place a thermometer in it
• Place the setup in a cold room (no less than 15ºC)
• Measure initial temperature
• Measure temperature after x amount of time (eg 20 mins)
• Have another test tube, in the same room, with the same amount but have the seeds boiled. Leave it for the same amount of time.
• Compare test tube 1 and 2. :)

Figure 2: Apparatus

Note that all images used in this post were created by me.

2.48 Describe experiments to investigate the effect of exercise on breathing in humans.

When you exercise, sometimes you end up respiring anaerobically as the body cannot get oxygen around quickly enough. Of course, this depends on the intensity of the exercise. This could be investigated as follows:

• Ask a friend to volunteer 
• At rest, have them lie down on the ground (belly up) and count how many times their chest rises in one minute. Record the result.
• Now, ask them to walk 100m (or any other given distance). Measure their breathing rate the same way as before. 
• Then ask them to run 100m. Measure breathing rate again.
• Finally, ask them to sprint 100m. Measure their breathing rate again.
• Wait until the person's breathing rate has returned to normal. Repeat the experiment from the start 3 times.
• Take an average of the results
• Plot a graph of your results
• Remember to keep the person, distance run, and environment the same.

Dependent variable: Breathing rate (breaths per minute)

Independent variable: Intensity of exercise

Control variables: Distance (100m), person doing the exercise (fitness must be the same), environment (i.e not have one in super hot conditions and another in freezing cold)

Note: results that differ by more that 0.2 should be ignored and should thus not be taken into consideration when taking an average.

An example graph can be seen below. THIS GRAPH DOES NOT EXPRESS THE RESULTS OF THE EXACT EXPERIMENT DESCRIBED but it does express the same idea.

Conclusion: As exercise intensity increases, the breathing rate increases as well.

Sometimes, the image doesn't show up, so the link to it can be found here

2.40 Understand that respiration continues during the day and night, but that the net exchange of carbon dioxide and oxygen depends on the intensity of light

Figure 1: Plant during the day

Yes, plants photosynthesize, but they respire too. They respire throughout the day and the night, because, of course, it is a living organism. As you should know, glucose is used in respiration, which the plant produces through photosynthesis :)

During the night, a plant only respires, as there is no sunlight. This means that it gives off carbon dioxide and does not re-absorb it. Similarly, during the night, oxygen will not be given off, as the plant is not photosynthesizing.

Remember: photosynthesis depends on light, but respiration never stops ^_^

Figure 2: Plant at night

2.39 Understand gas exchange (of carbon dioxide and oxygen) in relation to respiration and photosynthesis

In both photosynthesis and respiration, gas exchange occurs: one gas is swapped for another. They are the opposite of each other, which is why it works.

photosynthesis ~ carbon dioxide + water → glucose + oxygen
The plant, or whatever is photosynthesizing, is using the waste products of respiration, taking in carbon dioxide and giving out oxygen as a waste product.

respiration ~ glucose + oxygen → carbon dioxide + water
The organism is using the products of photosynthesis (although glucose can be obtained through food, so I guess that doesn't really work..... you probably shouldn't put that in your exam...sozzies), taking in oxygen and giving out carbon dioxide.

Because why not, here is a diagram

2.36 Write the word equation for anaerobic respiration in plants and in animals

In animals, it is:

glucose → lactic acid (+ energy)

In plants, it is:

glucose → ethanol + carbon dioxide (+ energy)

2.35 Write the word equation and the balanced chemical symbol equation for aerobic respiration in living organisms

Glucose + oxygen → carbon dioxide + water (+ energy)

C₆H₁₂O₆ + 6O₂    →    6CO₂ + 6H₂O (+ energy)

2.34 Describe the differences between aerobic and anaerobic respiration

Aerobic respiration is when an organism respires using oxygen and glucose is completely and fully broken down. This is used for movement, growth, etc. in humans. It is how we respire most of the time. This may be different in other organisms, or the same.

glucose + oxygen → carbon dioxide + water (+ energy)

Anerobic respiration is when an organism respires without using oxygen. Yeast, for example, naturally respires anerobically. In humans, however, we respire anerobically when the heart and lungs cannot work fast enough to provide enough oxygen around the body to break down that glucose. Instead, the body does not use oxygen, providing a fast, short burst of energy. This causes the build up of lactic acid (a waste product) in our muscles, which sometimes makes them sore. After respiring anerobically, as a human, you breathe heavily to make up for the oxygen lost. This can occur in other organisms too but may be different.

glucose → lactic acid (+ energy)

Figure 1: When you sprint, you respire anerobically. (Yes, that is Usain Bolt.)

2.33 Understand that the process of respiration releases energy in living organisms

All living things respire. (not to be confused with breathing) This occurs in the mitochondria of every cell, and produces energy for the organism. Even plants do this. It is the breaking down of glucose to produce energy.