Respiration

Time: 2 hours

Instructions

• Answer all questions.

• Show all calculations where necessary.

• Use clear and concise scientific explanations.

1. Section A

Choose the best answer for each question.

1. Which of the following statements about aerobic respiration is correct?

A) It occurs only in animal cells.
B) It does not require oxygen.
C) It produces more energy than anaerobic respiration.
D) It takes place in chloroplasts.

2. During respiration, glucose is broken down into:

A) Water and carbon dioxide
B) Oxygen and energy
C) Starch and water
D) Amino acids and carbon dioxide

3. What is the main function of ATP in cells?

A) Store genetic information
B) Provide energy for cellular processes
C) Carry oxygen in the blood
D) Convert glucose into proteins

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4. Which of the following is a product of anaerobic respiration in yeast?
A) Lactic acid
B) Ethanol
C) Oxygen
D) Starch

5. What happens to breathing rate during vigorous exercise?

A) It decreases to conserve oxygen
B) It remains constant
C) It increases to supply more oxygen to muscles
D) It stops once anaerobic respiration begins

6. Which substance accumulates in muscles during anaerobic respiration?

A) Glucose
B) Lactic acid
C) Oxygen
D) Carbon dioxide

7. Which process removes carbon dioxide produced during respiration?

A) Digestion
B) Excretion
C) Photosynthesis
D) Inhalation

8. Which of the following is the correct word equation for anaerobic respiration in human
muscles?
A) Glucose + Oxygen → Carbon dioxide + Water + Energy
B) Glucose → Lactic acid + Energy
C) Glucose → Ethanol + Carbon dioxide + Energy
D) Oxygen + Glucose → Water + Energy

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9. What is the main advantage of anaerobic respiration?
A) It produces more energy than aerobic respiration
B) It does not require oxygen
C) It prevents the production of lactic acid
D) It produces carbon dioxide

10. The purpose of mitochondria in a cell is to:

A) Store oxygen for respiration
B) Convert glucose into starch
C) Produce ATP through respiration
D) Absorb carbon dioxide

11. Why do athletes experience muscle fatigue during intense exercise?

A) Too much oxygen is available
B) Lactic acid builds up due to anaerobic respiration
C) Carbon dioxide accumulates in the muscles
D) Mitochondria stop producing ATP

12. Which of the following statements about the alveoli is correct?

A) They have thick walls to prevent gas exchange.
B) They contain muscle fibers to help air move in and out.
C) They have a large surface area for efficient diffusion.
D) They actively transport oxygen into the blood.

13. During inhalation, which of the following occurs?

A) The diaphragm relaxes and moves upward
B) The intercostal muscles contract, raising the ribcage
C) The pressure inside the lungs increases
D) The volume of the thoracic cavity decreases

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14. Which gas is transported in red blood cells by combining with hemoglobin?
A) Oxygen
B) Carbon dioxide
C) Nitrogen
D) Water vapor

15. Which of the following statements about carbon dioxide transport is correct?
A) Most carbon dioxide is carried as oxyhemoglobin in red blood cells.
B) Carbon dioxide is only dissolved in plasma and not carried in other forms.
C) Most carbon dioxide is transported as bicarbonate ions in the blood plasma.
D) Carbon dioxide is stored in the lungs before being exhaled.

16. How does smoking affect the alveoli?

A) It increases oxygen uptake.
B) It reduces surface area due to damage from tar.
C) It strengthens the walls of the alveoli.
D) It increases the flexibility of the bronchioles.

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2. Section B

1. (a) Define respiration. (2 marks)

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(b) Write the word equation for aerobic respiration. (2 marks)

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2. (a) List two differences between aerobic and anaerobic respiration. (2 marks)

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3. The table below shows the breathing rate of a person at rest and after exercise.

Condition Breathing Rate (breaths per minute)

At rest 16

After exercise 32

(a) Explain why the breathing rate increases after exercise. (3 marks)
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4. An athlete undergoes training to improve endurance. The table shows changes in their
heart rate before and after training.

Condition Resting Heart Rate (beats/min) Maximum Heart Rate (beats/min)

Before training 75 180

After training 65 190

(a) What happens to the athlete’s resting heart rate after training? (1 mark)

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(b) Why does the maximum heart rate increase after training? (3 marks)

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(c) Define cellular respiration. (2 marks)

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(d) How is the energy released from respiration stored for use in cells? (2 marks)

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(e) Why do plants also need to carry out respiration? (2 marks)

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5. (7 marks)

The table below shows some characteristics of two types of respiration

Type of Respiration Oxygen Required? Energy Released (kJ) Waste Products

X Yes 2900 Carbon dioxide, water

Y No 150 Lactic acid

(a) Identify respiration type X and type Y. (2 marks)

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(b) Which respiration type occurs in yeast and what are its products? (2 marks)
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6 .(6 marks)

A student measures their breathing rate at rest and after running for 5 minutes. The results are:

Condition Breathing Rate (breaths per minute)

At rest 16

After exercise 40

(a) Explain why the breathing rate increases after exercise. (3 marks)

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(b) How does an increase in breathing rate help muscle cells? (3 marks)

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7. (7 marks)

The diagram below shows a section of the alveoli in the lungs.

(Imagine a diagram showing alveoli, blood capillaries, and diffusion of gases.)

(a) Identify two adaptations of the alveoli that make gas exchange efficient. (2 marks)

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(b) Explain how oxygen moves from the alveoli into the blood. (3 marks)

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8. (7 marks)

The diagram below shows the position of the diaphragm during breathing.

(Imagine a diagram showing the diaphragm in both relaxed and contracted states.)

(a) Describe the role of the diaphragm in inhalation. (3 marks)

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(b) What happens to the ribcage and lung volume during exhalation? (2 marks)

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(c) How does the movement of air into the lungs demonstrate the principle of pressure changes?
(2 marks)

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9. (6 marks)

The table below shows the composition of inhaled and exhaled air.

Gas Inhaled Air (%) Exhaled Air (%)

Oxygen 21 16

Carbon dioxide 0.04 4

Nitrogen 78 78

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(a) Explain why there is a decrease in oxygen in exhaled air. (3 marks)

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(b) Why does carbon dioxide increase in exhaled air? (2 marks)

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(c) Why does the percentage of nitrogen remain the same? (1 mark)

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10 . (8 marks)

The following table shows the percentage of lung function in smokers and non-smokers.

Age Average Lung Function in Non-Smokers Average Lung Function in Smokers

(years) (%) (%)

20 100 100

30 95 90

40 90 78

50 85 65

60 80 50

(a) Explain how tar and carbon monoxide in cigarette smoke affect the lungs. (3 marks)

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