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Key Questions:

1. What equation represents anaerobic respiration in muscle cells?
   • Anaerobic respiration in muscles is represented by the equation: glucose -> lactic acid.
2. Why is less energy produced in anaerobic respiration compared to aerobic respiration?
   • As the oxidation of glucose is incomplete in anaerobic respiration much less Energy is transferred than in aerobic respiration.
3. What equation shows the anaerobic respiration in plant and yeast cells?
   • Anaerobic respiration in plant and yeast Cells is represented by the equation: glucose -> ethanol carbon dioxide.
4. What is anaerobic respiration in yeast cells also known as and why has it got economic importance?
   • Anaerobic respiration in yeast Cells is called fermentation and has economic importance in the manufacture of bread and alcoholic drinks.
5. What does the body react to during exercise?
   • During exercise the human body reacts to the increased demand for Energy.
6. What changes happen in the cardiovascular system when exercise increases and why?
   • The heart rate, breathing rate and breath volume increase during exercise to supply the muscles with more oxygenated blood.
7. When does anaerobic respiration take place in muscles?
   • If insufficient oxygen is supplied anaerobic respiration takes place in muscles.
8. What causes oxygen debt?
   • The incomplete oxidation of glucose causes a build up of lactic acid and creates an oxygen debt.
9. What happens to the muscles during long periods of vigorous activity?
   • During long periods of vigorous activity muscles become fatigued and stop contracting efficiently.
10. (HT) How is lactic acid converted back to glucose?
    • (HT only) Blood flowing through the muscles transports the lactic acid to the liver where it is converted back into glucose.
11. (HT) What is the oxygen debt?
    • (HT only) Oxygen debt is the amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the Cells.
12. How can metabolism be described?
    • Metabolism is the sum of all the reactions in a Cell or the body.
13. How are respiration and metabolism linked?
    • The Energy transferred by respiration in Cells is used by the organism for the continual enzyme controlled processes of metabolism that synthesise new molecules.
14. What processes are included in metabolism?
    • Metabolism includes: a) conversion of glucose to starch, glycogen and Cellulose, b) the formation of lipid molecules from a molecule of glycerol and three molecules of fatty acids. C) ? the use of glucose and nitrate ions to form amino acids which in turn are used to synthesise proteins. d) respiration. e) breakdown of excess proteins to form urea for excretion.
15. Why are sugars, amino acids, fatty acids and glycerol important in the synthesis of new materials?
    • Sugars are important as they join together to make carbohydrates, amino acids are the components of proteins and fatty acids and glycerol become lipids.