12. Respiration

Question 1

State some uses of energy in living organisms.

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Answer 1

• muscle contraction
• protein synthesis
• cell division
• active transport
• growth
• passage of nerve impulses
• maintenance of a constant body temperature

Question 2

Describe the effect of temperature on respiration in yeast.

Answer 2

1. rate of respiration increases with increasing temperature up to the optimum temperature
2. rate of respiration decreases after reaching optimum

Question 3

Why does the rate of respiration decrease in yeast after reaching optimum?

Answer 3

because the enzyme that catalyses the reaction is denatured at higher temperatures

Question 4

What is the optimum temperature for respiration of yeast?

Answer 4

30–40 °C

Question 5

Investigate the effect of temperature on respiration in yeast.

Answer 5

1. Take a beaker to serve as a water bath and a boiling tube with activated yeast suspension and sugar solution
2. Cover the boiling tube with a bung and connect the delivery tube
3. Place the boiling tube in the water bath
4. fill a second beaker with water at room temperature, immerse the other end of the delivery tube in this beaker
5. Pour water at 10 °C into the water bath: as the yeast respires, carbon dioxide bubbles will be seen in beaker 2
6. measure number of bubbles in 1 min
7. repeat changing temperatures

Question 6

Define aerobic respiration.

Answer 6

chemical reactions in cells that use oxygen to break down nutrient molecules to release energy

Question 7

Word equation for aerobic respiration

Answer 7

glucose + oxygen → carbon dioxide + water

Question 8

Balanced chemical equation for aerobic respiration

Answer 8

C6H12O6 + 6O2 → 6CO2 + 6H2O

Question 9

Define anaerobic respiration.

Answer 9

the chemical reactions in cells that break down nutrient molecules to release energy without using oxygen

Question 10

Which releases less energy per glucose molecule, aerobic or anaerobic?

Answer 10

anaerobic releases much less

Question 11

Anaerobic respiration releases much less…

Answer 11

energy per glucose molecule than aerobic

Question 12

Word equation for anaerobic respiration in yeast

Answer 12

glucose → alcohol + carbon dioxide

Question 13

glucose → alcohol + carbon dioxide

Answer 13

anaerobic respiration in yeast

Question 14

Word equation for anaerobic respiration in muscles during vigorous exercise

Answer 14

glucose → lactic acid

Question 15

glucose → lactic acid

Answer 15

anaerobic respiration in muscles during vigorous exercise

Question 16

Balanced chemical equation for anaerobic respiration in yeast

Answer 16

C6H12O6 → 2C2H5OH + 2CO2

Question 17

What builds up in muscles and blood during vigorous exercise?

Answer 17

lactic acid

Question 18

What does lactic acid cause?

Answer 18

oxygen debt

Question 19

What happens during vigorous exercise?

Answer 19

• cells cannot obtain enough oxygen for aerobic respiration only
• anaerobic respiration must happen too in muscle cells to provide them with energy to continue working

Question 20

What is oxygen debt?

Answer 20

the amount of oxygen needed to break down lactic acid in the liver

Question 21

How must lactic acid be broken down?

Answer 21

aerobic respiration in the liver to break down the lactic acid into carbon dioxide and water

Question 22

How is oxygen debt removed after exercise (3 ways)?

Answer 22

• continuation of fast heart rate to transport lactic acid in the blood (from muscles to the liver)
• continuation of deeper and faster breathing: supplies liver the oxygen it needs to break down the lactic acid
• aerobic respiration of lactic acid in the liver