Edexcel IGCSE Biology (g) Gas exchange Question Bank

Practise gas exchange through leaf and lung diagrams, indicator results, stomata calculations, ventilation mechanisms and CO2/O2 data.

Exam points

interpret indicator colours to link CO2 change with respiration and photosynthesis
explain leaf adaptations, stomata position and guard cell action using diagrams or photos
describe ventilation and lung effects using thorax pressure, alveoli and smoking data

Covered syllabus points

2.40B Diffusion in gas exchange 2.41B Gas exchange in respiration and photosynthesis 2.42B Leaf adaptations for gas exchange 2.43B Stomata in gas exchange 2.44B Light intensity and net gas exchange 2.45B Light and leaf gas exchange practical 2.46 Thorax structure 2.47 Ventilation muscles 2.48 Alveoli adaptations 2.49 Biological consequences of smoking 2.50 Ventilation practical

[Maximum number: 2]

Read the passage below. Use the information in the passage and your own knowledge to answer the questions that follow.

Physic Gardens

The photograph shows a physic garden. Physic gardens are places where people grow many types of plants that produce medicinal drugs.

Figure for Question (g) Gas exchange question 1 — Edexcel IGCSE Biology

People have grown medicinal plants in physic gardens for thousands of years. It was estimated in 2016 that out of 30000 plant species that are known to be useful to humans, 17000 of these plant species have medicinal uses.

Medicinal plants produce a wide range of types of drugs including alkaloids, glycosides, terpenes and polyphenols.

Alkaloids are bitter-tasting, alkaline chemicals found in many different plant species. Alkaloids are often toxic in high doses so care needs to be taken when using them. Examples of alkaloids are caffeine and quinine. Caffeine, found in tea and coffee, can stimulate the adrenal glands. Quinine from the bark of the cinchona tree has been used for many centuries to kill the parasite that causes malaria.

An example of a glycoside drug is senna. This drug is extracted from the Senna plant and is used to treat constipation. The drug affects muscles in the intestine.

Terpenes are chemicals that often have strong smells. Terpenes are thought to have evolved to prevent herbivore animals from eating certain plants. An example of a plant that produces terpenes is thyme. The terpenes in thyme have an antiseptic effect which means they can be used to sterilise wounds.

Phytoestrogens are molecules found in plants such as angelica and have been used for many years to treat problems with human fertility. Examples of polyphenols are phytoestrogens, taxol and curcumin. Polyphenols have many roles within plants and many are used as medicines. Taxol is a drug extracted from yew trees and is used to prevent cell division in human body cell tumours.

Curcumin is a drug produced by the turmeric plant. Curcumin can help widen the airways to the lungs so can help people with asthma breathe.

Scientists are looking to reproduce many of these drugs artificially. They are developing genetically modified bacteria containing genes that will allow these drugs to be mass produced in fermenters.

Some people have a condition called asthma. This condition causes the person's airways to become narrow.

Explain why consuming curcumin can improve the concentration of oxygen in the blood of people who have asthma (lines 25 to 26).

[Maximum number: 9]

The diagram shows parts of the human respiratory system with some structures labelled.

Figure for Question (g) Gas exchange question 2 — Edexcel IGCSE Biology

(a)

Which of these is the structure labelled X ?

alveolus

bronchiole

bronchus

trachea

[ 1 ]

(b)

Explain how contraction of the diaphragm causes air to move into the lungs.

[ 3 ]

(c)

A scientist compared the rate at which oxygen is used during exercise by a person who is a non-smoker with a person who is a smoker.

The rate is measured in $\mathrm{cm}^{3}$ per minute for each kilogram of body mass.
The table shows the scientist's results.

Table for Question (c) — Edexcel IGCSE Biology

[ 5 ]

(i)

Calculate the volume of oxygen used in 30 minutes by a non-smoker with a mass of 70 kg .
volume =…… $\mathrm{cm}^{3}$

[ 2 ]

$35 \times 70 \times 30=73500\left(\mathrm{~cm}^{3}\right)$

One mark for $\times 35$ or $\times 70$ or $\times 30$ or 2450 or 1050 or 2100

Accept 74000 or 73000 for two marks

Correct answer gains both marks

(ii)

Explain the effect of cigarette smoking on the rate at which oxygen is used.

[ 3 ]

[Maximum number: 2]

The diagram shows a section through a leaf with different parts labelled P to U .

Figure for Question (g) Gas exchange question 3 — Edexcel IGCSE Biology

The photograph shows water lilies, plants that float on the surface of ponds.

Suggest why the leaves of the water lily only have stomata on their upper surface.

An answer that makes reference to two the following points:

- lower surface in water / upper in air / stomata would be in water / eq

- (stomata) able to absorb $\mathrm{CO}_{2} /$ gases (by diffusion) / allows gas exchange

- (stomata) able to lose water (by transpiration / evaporation) / to allow transpiration

All question bank results loaded

Covered syllabus points

(g) Gas exchange question 1

(g) Gas exchange question 2

Question (a)

Question (b)

Question (c)

Question (i)

Question (ii)

(g) Gas exchange question 3