2. Biological molecules
A section of Biology, 9700
Listing 10 of 748 questions
Asthma is a disease of the respiratory system. • During an asthma attack the membranes lining the airways release mucus and become inflamed. • This causes the muscles of the airways to contract and narrow the lumen of the airways, making breathing difficult. • Most asthma attacks are triggered by allergens. • Allergens are harmless substances that, in some people, stimulate an immune response that leads to an allergic reaction. • There has been a large increase in cases of asthma over the last 40 years. Many allergens that can trigger an asthma attack are inhaled during normal breathing. Suggest two examples of these allergens. Over the past 20 years a study has been carried out on the 261 inhabitants of a remote island in the South Atlantic called Tristan da Cunha. • There are only seven different family names on the island. • Half of the islanders displayed symptoms of asthma. • A gene, ESE3, is responsible for the normal deposition of collagen in the walls of the airways. • When the gene is faulty, too much collagen is produced and this can lead to asthma-like symptoms, making breathing difficult. • This faulty gene has been found among the inhabitants of Tristan de Cunha. Collagen is also found in the walls of blood vessels. State one property of collagen that enables it to carry out its main function in the walls of blood vessels and airways. Suggest why this form of asthma was very common amongst the population of Tristan da Cunha.
9700_w11_qp_41
THEORY
2011
Paper 4, Variant 1
View
Asthma is a disease of the respiratory system. • During an asthma attack the membranes lining the airways release mucus and become inflamed. • This causes the muscles of the airways to contract and narrow the lumen of the airways, making breathing difficult. • Most asthma attacks are triggered by allergens. • Allergens are harmless substances that, in some people, stimulate an immune response that leads to an allergic reaction. • There has been a large increase in cases of asthma over the last 40 years. Many allergens that can trigger an asthma attack are inhaled during normal breathing. Suggest two examples of these allergens. Over the past 20 years a study has been carried out on the 261 inhabitants of a remote island in the South Atlantic called Tristan da Cunha. • There are only seven different family names on the island. • Half of the islanders displayed symptoms of asthma. • A gene, ESE3, is responsible for the normal deposition of collagen in the walls of the airways. • When the gene is faulty, too much collagen is produced and this can lead to asthma-like symptoms, making breathing difficult. • This faulty gene has been found among the inhabitants of Tristan de Cunha. Collagen is also found in the walls of blood vessels. State one property of collagen that enables it to carry out its main function in the walls of blood vessels and airways. Suggest why this form of asthma was very common amongst the population of Tristan da Cunha.
9700_w11_qp_42
THEORY
2011
Paper 4, Variant 2
View
is a photomicrograph of a section through the lungs showing a bronchus and some alveoli. tissue Y tissue X State the function of tissue X labelled in . Describe how the distribution of tissue X in the trachea differs from that shown in . Describe how the epithelial tissue, Y, is adapted for its function. is a photograph of two African elephants, Loxodonta africana. Describe the difference in surface area to volume ratio between the adult elephant and baby elephant shown in . Suggest why animals such as elephants require a gas exchange system. The feet of elephants are protected by structures under the skin known as cushions. The cushions are made up of a large number of cells surrounded by connective tissue containing many fibres of collagen. The fibres help to maintain the structure of the cushion. The collagen fibres are made of collagen molecules. Describe the structure of a collagen molecule. The cushion in the foot is very strong and is able to resist extremely large forces acting on it due to the large mass of the elephant. Suggest how the structure of a collagen fibre can help the cushion resist these large forces.
9700_w20_qp_21
THEORY
2020
Paper 2, Variant 1
View
Questions Discovered
748