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CIE iGCSE Co-Ordinated Science B12. Respiration Exam Style Questions Paper 3

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Question

(a) Fig. 3.1 is a diagram of the human breathing system.
(i) Identify the parts labelled P and Q in Fig. 3.1.
(ii) On Fig. 3.1 draw a label line and the letter D to identify the diaphragm.
(iii) Complete the sentence to describe aerobic respiration.
Aerobic respiration is the chemical reaction in cells that uses ………………………. to break down nutrient molecules to release energy.
(iv) Some of the energy released by aerobic respiration is used in active transport. State two other uses of the energy released from aerobic respiration in living organisms.
(b) Cystic fibrosis is an inherited condition that affects the gas exchange system.
(i) A person with cystic fibrosis produces thick sticky mucus in their gas exchange system. Their ciliated cells have difficulty moving this sticky mucus.
State one part of the gas exchange system where ciliated cells are found.
(ii) Cystic fibrosis is caused by a recessive allele, f.
        Two people that do not have cystic fibrosis have a child with cystic fibrosis.
    Complete the Punnett square to show why the child has cystic fibrosis.
(iii) Identify if the mother’s genotype in part (b)(ii) is heterozygous or homozygous. Circle the correct answer.
heterozygous       homozygous
Explain your answer.

Most-appropriate topic codes (Cambridge IGCSE Coordinated Sciences 0654):

• Topic B11.1 — Gas exchange in humans (Part (a)(i), (a)(ii), (b)(i))
• Topic B12.1 — Respiration (Part (a)(iii), (a)(iv))
• Topic B16.3 — Monohybrid inheritance (Part (b)(ii), (b)(iii))

▶️ Answer/Explanation

(a)(i) P – rib; Q – alveolus / alveoli
The ribs (P) protect the lungs and move during breathing. Alveoli (Q) are tiny air sacs where gas exchange occurs between air and blood.

(a)(ii) Diaphragm labelled D
The diaphragm is a dome-shaped muscle at the base of the chest cavity that contracts and relaxes to change the volume of the thorax during breathing.

(a)(iii) oxygen
Aerobic respiration requires oxygen as the final electron acceptor in the electron transport chain, allowing complete breakdown of glucose to carbon dioxide and water.

(a)(iv) Any two from: muscle contraction; protein synthesis; cell division; growth; the passage of nerve impulses; the maintenance of a constant body temperature
Energy from respiration is used for many cellular processes including mechanical work, biosynthesis, and maintaining homeostasis.

(b)(i) trachea / bronchi
Ciliated cells line the airways (trachea and bronchi). Their cilia beat to move mucus upwards, removing trapped particles and pathogens.

(b)(ii) Father’s genotype: Ff; Offspring genotypes: FF, Ff, Ff, ff
Both parents must be carriers (Ff) to have a child with cystic fibrosis (ff). The Punnett square shows a 1 in 4 chance of the child inheriting two recessive alleles.

(b)(iii) heterozygous and has two different alleles
The mother’s genotype is Ff, meaning she has one dominant allele (F) and one recessive allele (f), which is the definition of heterozygous.

Question

Fig. 3.1 is a diagram of a palisade cell from a potato plant.
(a)(i) Identify all the structures, labelled in Fig. 3.1, that are also in animal cells.
      (ii) Describe the functions of the cytoplasm and the cell wall.
(b) Aerobic respiration takes place in mitochondria to release energy.
      (i) State the word equation for aerobic respiration.
      (ii) State one use of energy from respiration in living organisms.
(c) A student cuts a small piece of potato.
The student measures the mass of the piece of potato.
The student puts the piece of potato in pure water (water with no chemical impurities).
Describe the effect of the pure water on the mass of the piece of potato.
Include the name of the process in your answer.
(d) Plants are made up of different parts.
Use words from the list to complete the sentence about plants.
organs        tissues        cells        organ systems
Plant leaves are thin, flat …………………… made up of …………………… including phloem and epidermis.

Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):

• Topic B2.1 — Cell structure (Part (a)(i))
• Topic B2.1 — Cell structure (Part (a)(ii))
• Topic B12.1 — Respiration (Part (b))
• Topic B3.2 — Osmosis (Part (c))
• Topic B2.1 — Cell structure (Part (d))

▶️ Answer/Explanation

(a)(i) cell membrane, cytoplasm, mitochondria, nucleus
These structures are found in both plant and animal cells. Chloroplasts, cell walls and large vacuoles are present only in plant cells.

(a)(ii) Cytoplasm: site of metabolic/chemical reactions ; Cell wall: protects/supports the cell
The cytoplasm is where most cellular reactions occur. The cell wall provides structural support and protection, maintaining the shape of the cell.

(b)(i) glucose + oxygen → carbon dioxide + water
Aerobic respiration uses glucose and oxygen to release energy, producing carbon dioxide and water as waste products.

(b)(ii) Protein synthesis / cell division / growth / muscle contraction / passage of nerve impulses / maintenance of constant body temperature / active transport
Energy from respiration is used for many essential life processes including growth, movement and active transport across cell membranes.

(c) Water moves into the potato tissue ; mass increases ; osmosis
Pure water has a higher water potential than the potato cells. Water moves into the potato cells by osmosis through the partially permeable cell membrane, causing the mass to increase.

(d) Plant leaves are thin, flat organs made up of tissues including phloem and epidermis.
Leaves are organs composed of different tissues such as epidermal tissue and vascular tissue (phloem and xylem).

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