Detailed and comprehensive notes on gas exchange (Edexcel biology A). [“A-Level Biology: Edexcel A Year 1 & 2 Complete Revision & Practice” (CGP, ISBN: 2986), “Salters-Nuffield AS/A level Biology Student Book 1” (Pearson, ISBN: 1007) and “Salters-Nuffield A level Biology Student Book 2”...
Gas Exchange
2.1 i) Know the properties of gas exchange surfaces in living organisms (large surface area to volume
ratio, thickness of surface, difference in concentration).
ii) Understand how the rate of diffusion is dependent on these properties and can be calculated using
Fick’s Law of Diffusion.
iii) Understand how the structure of the mammalian lung is adapted for rapid gaseous exchange.
Fick’s Law
• Rate of diffusion is directly proportional to surface area.
• Rate of diffusion is directly proportional to concentration gradient.
• Rate of diffusion is inversely proportional to diffusion distance.
How is the Alveolus Adapted to Gas Exchange?
1. High Surface Area
• The shape of the alveolus provides a large surface area : volume ratio.
• Quantitiy – there are millions of alveoli in the lungs.
2. Short Diffusion Distance
• Both the alveolar epithelium and capillary endothelium are one cell thick.
• The lumen of the capillary is narrow, which pushes the erythrocytes up against the capillary endothelium.
3. High Concentration Gradient
• Ventilation – inhalation brings air (oxygen) to alveolus; the alveolar air space has a higher concentration
of oxygen than the blood in the capillary, so oxygen diffuses across the membrane.
The Lungs
• Oxygen diffuses out of the alveoli, across the
alveolar epithelium and the capillary endothelium,
into the blood.
• Carbon dioxide diffuses into the alveoli from the
blood and is breathed out.
4
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller JunaidAli025. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £0.00. You're not tied to anything after your purchase.
