A) Name the chemical substance that accumulates in the muscles during strenuous physical exercise b) Briefly describe how the chemical substance named in (a) above is formed c) State two effects of ac

Here are the answers to your questions:

13. a) Name the chemical substance that accumulates in the muscles during strenuous physical exercise

• Lactic acid

b) Briefly describe how the chemical substance named in (a) above is formed
Lactic acid is formed during anaerobic respiration when muscles do not receive enough oxygen for aerobic respiration. Glucose is incompletely broken down into lactic acid to produce a small amount of ATP.

c) State two effects of accumulation of the chemical substance named in (a) above in the muscles

1. It causes muscle fatigue, leading to a burning sensation and reduced muscle performance.
2. It lowers the pH of muscle cells, which can inhibit enzyme activity and muscle contraction.

14. The diagram below represents an organ found in certain vertebrates. Study it.

a) Identify the above organ

• Gill

b) Name three structures in members of class Amphibia that play similar role as the above organ

1. Skin
2. Lungs
3. Buccal cavity lining (or mouth lining)