1. What is the difference between aerobic and anaerobic respiration ?
Answer
Aerobic respiration uses oxygen, and anaerobic happens without oxygen.
2. Write the word equation for anaerobic respiration in plants and yeast.
Answer
glucose ➔ ethanol + carbon dioxide
3. Give the chemical symbol for glucose.
Answer
The chemical symbol for glucose is C6H12O6
4. Describe some differences between aerobic and anaerobic respiration in humans.
Answer
Anaerobic respiration transfers less energy than aerobic respiration. Aerobic respiration uses oxygen, but anaerobic respiration is without oxygen. Aerobic respiration produces carbon dioxide and water, but anaerobic respiration produces lactic acid.
5. Describe what happens to the lactic acid that builds up during anaerobic respiration in muscles.
Answer
Lactic acid is transported from the muscles to the liver, where it is converted back into glucose by an oxidation reaction.
6. Design an investigation to test the hypothesis: "The heart rate of people who do not exercise regularly will take longer to return to normal after exercise than the heart rate of people who exercise regularly."
Answer
Take two groups of people, 10 who exercise once a week and 10 who exercise three or more times a week. Match the groups so that they are the same age and gender. Ask all of the people to sit quietly for five minutes and then find their resting heart rate in beats per minute. Make all of the people do the same exercise for the same length of time, for example, running on a treadmill for three minutes. Measure theheart rate every 30 seconds and record the time it takes to return to the resting rate. Calculate the mean time taken for the heart rate to return to its resting rate for each group, and compare the times for the two groups.
7. Name the molecule that can be synthesised from glycerol and three fatty acids.
Answer
Lipids are synthesised from glycerol and three fatty acids.
8. Why the metabolic rate is highest under 20 years of age ?
Answer
During growth, there is a high rate of respiration to provide energy and a high rate of synthesis reactions to produce proteins, both of which are essential for growth.
9. The figure below shows the apparatus a student used to investigate the effect of temperature on the rate of anaerobic respiration in yeast. Suggest two control variables the student used.
Answer
Same volume of yeast and same volume (or concentration) of sugar.