Introduction

Transport of substances such as oxygen, nutrients and waste is essential in any organism. Some can rely on diffusion, however in multicellular organisms the low surface area to volume ratio makes the diffusion distance to the cells in the middle far too long to sustain. This leads to mass transport systems such as our circulatory system.

You will be studying the functions of different parts of the blood, something you will have covered at IGCSE, but the key difference now is that you also need to know the chemical mechanisms by which oxygen is taken up and released, the effect of excess carbon dioxide, and the cascade of elements that allow clotting.

Reading

Edexcel AS/A Level Biology Student Book 1 pages 26 to 36, page 49

Read and Make Notes

Read pages 26 to 30, making appropriate notes and answering the ‘in-text’ questions.

Consolidate

Now consolidate your understanding by working through these additional resources:

WATCH – Circulatory System (Khan Academy)

WATCH – Asellus Blood Flow (Twig)

Read and Make Notes

Read pages 31 to 36, making appropriate notes and answering the ‘in-text’ questions.

Consolidate

Now consolidate your understanding by working through these additional resources:

WATCH – What is Blood? (YouTube)

REVIEW – Haemoglobin Dissociation Curves Poster

REVIEW – Blood Clotting Poster

WATCH – Red Blood Cells (Khan Academy)

WATCH – Haemoglobin (Khan Academy)

Make Notes Icon.png Tasks

Complete the following:

Complete questions 4 and 7 on page 49.

Top Tips

Make sure that you understand the following key points:

Be able to connect the features of mass transport systems (structure) with the way they facilitate diffusion (function).
When you discuss oxygen dissociation curves, remember to focus on the most relevant parts of the graph for that particular situation. For example, in the lungs, discuss the ability of haemoglobin to pick up oxygen at high levels of oxygenation (the top end of the graph), and don’t bother talking about dissociation rates. When discussing the release of oxygen in respiring tissues, only talk about the low affinity for oxygen at low partial pressures (the bottom end of the graph).

Know the clotting sequence well and in order.

Key Terms

Check that you know all of the terms in the Subject Vocabulary boxes on pages 30 and 36 and add any you don’t know to your glossary.

Quiz

Complete Quiz 01: Biochemistry and Circulation. If you score less than 90%, try again.

Assignment

When you have completed all the activities and are fully prepared and feel confident with the material, you should complete Assignment One and submit it to your tutor via Canvas for marking and feedback.