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Combined Science: Biology

GCSE · Edexcel · higher

QuestionsFlashcards

Disease
Defence Against Disease
Development of Medicines
- Antibiotics
  4
- Discovery & Development of New Drugs
  6
Non-Communicable Diseases
- Lifestyle & Non-Communicable Disease
  8
- Cardiovascular Disease
  6

The Organism in the Environment
Human Influences on the Environment
- Human Impact on Biodiversity
  6
- Benefits of Maintaining Biodiversity
  6
Cycles within Ecosystems

Gas Exchange Flashcards

All 7 cards in this deck

At the alveolus, which gas moves from the alveolus into the capillary, and which moves from the capillary into the alveolus?: Oxygen ( $\mathrm{O_2}$ ) moves alveolus → capillary; carbon dioxide ( $\mathrm{CO_2}$ ) moves capillary → alveolus.
How do gases move from an alveolus into a capillary?: By diffusion, down a concentration gradient (high to low concentration), through a membrane.
True or false? Breathing faster during exercise helps keep a steep oxygen concentration gradient at the alveoli.: True. Ventilation replaces alveolar air with fresh air high in oxygen, and blood flow carries oxygenated blood away, so more oxygen is absorbed into the blood for respiration.
Why is the wall of an alveolus only one cell thick?: It gives a short diffusion distance, so gases diffuse across quickly.
How do the millions of tiny alveoli in the lungs help gas exchange?: They provide a very large surface area for diffusion, so more gas can diffuse each second.
What is the advantage of red blood cells passing slowly and one at a time through a narrow alveolar capillary?: They are held close to the capillary wall, reducing the diffusion distance, and the slower flow gives more time to diffuse, maximising the oxygen taken up.
Why do the alveoli have a moist lining?: Oxygen and carbon dioxide dissolve in the moisture before they diffuse across the alveolus and capillary walls.