By Martin Rowland, Steve Potter
Ideal for revision, those publications clarify the unit standards, summarise the content material and contain specimen questions with graded answers.
Martin Rowland has taught and tested A-level Biology for over 30 years and is presently a Chair of Examiners in Biology. he's co-author of the profitable titles AQA Biology for AS and AQA Biology for A2, released through Hodder schooling.
Read Online or Download AQA AS Biology Student Unit Guide : Unit 1 Biology and Disease PDF
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Extra resources for AQA AS Biology Student Unit Guide : Unit 1 Biology and Disease
Toxins in cigarette smoke provoke an inflammatory response, which leads to the breakdown of the walls of the alveoli. Figure 41 shows how this reduces the area of the gas exchange surface. 44 AQA AS Biology The lungs, breathing and gas exchange Healthy alveoli Alveoli in person with emphysema Many small alveoli with a large surface area for gas exchange Walls of alveoli damaged, resulting in fewer larger alveoli with a reduced surface area for gas exchange Figure 41 Emphysema reduces the surface area for gas exchange The amount of elastin (a protein) in the tissues surrounding the airways is also reduced.
They can remain in this condition for many years — people are infected, but show no symptoms and do not infect other people. ●● If the bacteria become active again, the tubercles grow and may invade a Knowledge check 23 bronchus (allowing the bacteria to spread to other parts of the lungs) or an How will cavities in the lungs caused by tuberculosis reduce (a) the effectiveness of ventilation and (b) the rate of gas exchange? artery (allowing the bacteria to spread to other parts of the body and create secondary infections).
Artery (allowing the bacteria to spread to other parts of the body and create secondary infections). This is active tuberculosis. The rapid multiplication of the bacteria at this stage results in the formation of cavities in the lung, which gave the disease its common name of ‘consumption’. ●● Cavities in the lung reduce both the effectiveness of ventilation and the rate of gas exchange in the alveoli. Symptoms of TB include: ●● chest pain and coughing up blood ●● a cough that lasts for more than 3 weeks ●● chills and fever ●● night sweats ●● loss of appetite and loss of weight ●● fatigue People most at risk of infection include those who: ●● Knowledge check 24 Why does an inadequate diet and infection by HIV increase the risk of infection by TB?
AQA AS Biology Student Unit Guide : Unit 1 Biology and Disease by Martin Rowland, Steve Potter