1. Unit 2: The continuation of life
Higher Human Biology
Unit 2: The continuation of life
Chapter 21:
Delivery of Oxygen to Cells
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Mrs Smith Ch21 The Delivery of Oxygen to Cells.

2. Mrs Smith Ch21 The Delivery of Oxygen to Cells.
Learning Intentions
Success Criteria
To understand how oxygen and nutrients are delivered by the bloodstream to every living cell in the body.
State the equation for the reversible reaction between oxygen and haemoglobin
Explain the affinity of haemoglobin for oxygen in relation to:
i) changes in blood oxygen tension
ii) changes in temperature
Use oxygen dissociation curves to explain the affinity for oxygen in relation to:
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Mrs Smith Ch21 The Delivery of Oxygen to Cells.

3. Introduction
Human cells are bathed in tissue fluid. Delivery of essential materials to within DIFFUSION DISTANCE of cells is brought about by the circulatory system.
Since blood plasma consists of water and dissolved solutes, it would seem reasonable to expect that materials to be transported would need to be highly soluble in water.
THE PROBLEM IS
THIS IS NOT THE CASE
WITH OXYGEN.

4. 1. Haemoglobin
As oxygen is only slightly soluble in water only a little could be carried by blood plasma to the cells, this would be inadequate to satisfy the needs of respiring cells. This problem is solved by the presence of haemoglobin.
Instead, haemoglobin (a respiratory pigment) combines with oxygen increasing the oxygen-carrying capacity of the blood.

5. Structure of Haemoglobin
In humans, haemoglobin molecules have 4 haem (a compound containing iron) groups and globin (a protein made of several polypeptide chains).
Each haem group is able to carry 1 Oxygen molecule.
Polypeptide chains
Haem group
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Mrs Smith Ch21 The Delivery of Oxygen to Cells.

6. Haemoglobin molecule showing 4 haem groups.
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Mrs Smith Ch21 The Delivery of Oxygen to Cells.

7. 2. Association and Dissociation
To be effective a respiratory pigment must be able to
combine easily (associate) with oxygen when the oxygen concentration in the surroundings is high
rapidly release (dissociate) oxygen when the surrounding oxygen concentration is low.
Haemoglobin has a HIGH AFFINITY for oxygen when the oxygen concentration in the surrounding environment is high (e.g. lungs) and a LOW AFFINITY for oxygen when the oxygen concentration is low (e.g. active cells).
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Mrs Smith Ch21 The Delivery of Oxygen to Cells.

8. Association and Dissociation
Dissociate = to rapidly release Oxygen
(when surrounding O2 Concentration is low)
e.g. at respiring cells
Image source:
Associate = to combine readily with Oxygen
(when surrounding O2 Concentration is high)
e.g. at lungs
Affinity = tendency to combine with a substance.

9. The Combining of Haemoglobin with Oxygen to give OXYHAEMOGLOBIN+
Oxyhaemoglobin
Dissociation (in tissues)
Association
(in lungs)
Haemoglobin
This chemical reaction is reversible
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10. Mrs Smith Ch21 The Delivery of Oxygen to Cells.
Oxygen Tension
The partial pressure (tension of oxygen is a measure of its concentration and is expressed in kilopascals (kPa).
The oxygen tension of inhaled alveolar air, for example, is about 13kpa.
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Mrs Smith Ch21 The Delivery of Oxygen to Cells.

11. Oxygen Dissociation Curve
Percentage saturation of haemoglobin with oxygen decreases with decreasing oxygen tension of the surroundings.
However the relationship between the two in not a linear one.
Lets at the Oxygen Dissociation curve.
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Mrs Smith Ch21 The Delivery of Oxygen to Cells.

12. Oxygen Dissociation Curve
When graphed it gives an S-shaped curve this is called the oxygen dissociation curve,
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Mrs Smith Ch21 The Delivery of Oxygen to Cells.

13. Oxygen Dissociation Curve – Extreme right
At the extreme right hand side, the oxygen tension of inhaled alveolar air is high (~12 kPa) and haemoglobins level of saturation is close to 100%
Association
Dissociation

14. Oxygen Dissociation Curve – Moving Gradually left
Moving gradually to the left along the graph, the oxygen concentration of the surroundings is found to decreased yet haemoglobin still remains loaded up with oxygen to levels over 85% saturation even when the oxygen tension of the surroundings has dropped to 8kPa. This is due to the fact that haemoglobin has a high affinity for oxygen.
Association
Dissociation

15. Oxygen Dissociation Curve – Extreme Left
At the extreme Left hand side, the oxygen tension drops to below 6kPa and the percentage saturation of haemoglobin with oxygen drops rapidly.
This is because haemoglobin’s affinity for oxygen decreases rapidly in surroundings of low oxygen concentration. As a result it unloads its oxygen. This process is represented by the step part of the S-shaped dissociation curve.
Association
Dissociation

16. Mrs Smith Ch21 The Delivery of Oxygen to Cells.
Respiring cells
Actively respiring cells consume much oxygen and the oxygen tension is found to be low (2.7kPa or less. At the other extreme the oxygen tension of alveolar air is high at about 13 Kpa.
When haemoglobin from respiring cells returns to the lungs, it becomes loaded up with oxygen which moves along the diffusion gradient from alveoli to blood. This process of association continues as before until haemoglobin is almost 100% saturated.
When haemoglobin is transported to actively respiring cells with an oxygen tension of 2.7kPa haemoglobins percentage saturation with oxygen drops to a low level (about 35%). This is because haemoglobin rapidly dissociates from oxygen and unloads it. As a result oxygen becomes available to satisfy the demands of actively respiring cells.
19/04/2017
Mrs Smith Ch21 The Delivery of Oxygen to Cells.

17. Mrs Smith Ch21 The Delivery of Oxygen to Cells.
Resting cells
Cells at rest do not consume much oxygen as actively respiring cells. The oxygen tension of cells at rest is therefore around 5.3kPa.
When blood with an oxygen tension of 13kPa from the lungs arrives at resting cells, its oxygen tension drops to 5.3kPa.
Haemoglobin now unloads its oxygen by disassociation until its percentage saturation is about 75%.
Blood with an oxygen tension of 5.3kPa and haemoglobin which is still 75% saturated with oxygen then returns to the lungs and loads up again by association to almost 100% and so on.
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Mrs Smith Ch21 The Delivery of Oxygen to Cells.

18. The effectiveness of haemoglobin
The oxygen dissociation curve is especially steep between oxygen tensions of 6 an 2pKa.
This means that any slight drop in oxygen tension of body cells within this range results in a rapid release of oxygen by haemoglobin of these cells.
So effective is haemoglobin at this loading up (association) and unloading (dissociation) of oxygen, that it is responsible for the transport of 97% of the oxygen carried in the bloodstream.

19. The Effect of Temperature
As the temperature of blood increases, haemoglobin’s affinity for oxygen decreases, so it unloads oxygen sooner at high temperatures
Cells in need of more O2 rise in temperature triggering the release of O2 from haemoglobin
e.g. respiring cells & tissues suffering microbial infection.

20. Mrs Smith Ch21 The Delivery of Oxygen to Cells.
Significance
Large quantities of energy is generated by inflamed tissues suffering microbial infection.
The rise in temperature that occurs locally in these tissues triggers the release of extra oxygen from haemoglobin.
This is advantageous since these cells are exactly where extra oxygen is required for aerobic respiration.
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Mrs Smith Ch21 The Delivery of Oxygen to Cells.

21. Fetal Haemoglobin
Foetal haemoglobin releases its O2 less readily (at a lower range of O2 tension values) than adult haemoglobin.
So, fetal haemoglobin has a higher affinity for O2 allowing it to draw O2 from its mothers bloodstream across the placenta.

22. Mrs Smith Ch21 The Delivery of Oxygen to Cells.
Learning Intentions
Success Criteria
To understand how oxygen and nutrients are delivered by the bloodstream to every living cell in the body.
Describe the features of a red blood cell: (biconcave shape dimensions, no nucleus, flexibility).
Relate the features of a red blood cell to the cell’s ability to absorb oxygen.
Describe the life history of a red blood cell to include:
i) site of production
ii) life span
iii) factors required for production
iv) sites of breakdown
v) fate of the products of breakdown
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Mrs Smith Ch21 The Delivery of Oxygen to Cells.

23. STRUCTURE OF A RED BLOOD CELLS
Cytoplasm rich in haemoglobin
Small size (7 μm)
No nucleus
Flexible to pass through capillaries
Biconcave shape so large surface area so efficient absorption of oxygen.

24. Mrs Smith Ch21 The Delivery of Oxygen to Cells.
HEALTHY RED BLOOD CELLS ARE SMALL (the actual size of a red blood cell is approx 2 micron at the rim by 7 micron in diameter)
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Mrs Smith Ch21 The Delivery of Oxygen to Cells.

25. Mrs Smith Ch21 The Delivery of Oxygen to Cells.
RED BLOOD CELLS
THEY ARE PRODUCED IN THE BONE MARROW FROM STEM CELLS AND LAST FOR 120 DAYS.
THEY REQUIRE IRON FOR THEIR FORMATION.
THEY REQUIRE VITAMIN B12 FOR THEIR FORMATION.
LACK OF IRON OR B12 RESULTS IN ANAEMIA.
INTRINSIC FACTOR SECRETED BY THE STOMACH IS REQUIRED TO AID B12 ABSORPTION.
LACK OF INTRINSIC FACTOR RESULTS IN PERNICIOUS ANAEMIA.
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Mrs Smith Ch21 The Delivery of Oxygen to Cells.

26. Mrs Smith Ch19 The need for transport
Essay Questions: SQA 2002 & 2007
2002 Give an account of the life history of a red blood cell (10) 2007 Give an account of how the structure of a red blood cell relates to its function. (10)
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Mrs Smith Ch19 The need for transport

27. Essay Questions: Guide to H Grade essays pg81
Red blood cells are amongst the most unusual and plentiful cells in the human body. Write an account of these cells with reference to the following:
Relationship between structure and function (6).
Production and eventual breakdown (9).
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Mrs Smith Ch19 The need for transport

28. Production of Red Blood Cells
Red blood cells are produced in the red bone marrow.
Red bone marrow consists of stem cells
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Mrs Smith Ch21 The Delivery of Oxygen to Cells.

29. Production of Red Blood Cells
Bone marrow is distributed throughout skeleton in children
just in sternum, ribs, vertebrae & long bones in adults
Marrow contains undifferentiated cells (stem cells), which divide by mitosis then become specialised .

30. 9. Nutritional factors: Vitamins & Minerals
Vitamin B12 – needed for production of Red Blood Cells (RBCs) in the bone marrow.
Deficiency in either prevents RBC production so leads to anaemia, because the blood can’t carry enough oxygen
Iron – needed for haemoglobin formation

31. No intrinsic factor leads to pernicious anaemia
Vitamin B12 – gets absorbed by the gut if intrinsic factor, a type of chemical secreted by the stomach, is present.
No intrinsic factor leads to pernicious anaemia

32. 10.Destruction of Red Blood Cells
A red blood cell lives for about 120 days.
Has no nucleus or ribosomes so can’t make proteins so no growth & repair can occur.
The red blood cells fragments (become damaged) in the capillaries.
Liver
Bone marrow
Spleen
Macrophages destroy old RBCs by phagocytosis

33. 10. Destruction of Red Blood Cells
Worn out red blood cells are destroyed by macrophages by the process of phagocytosis in the liver, bone marrow and spleen.
Haemoglobin molecules are broken down and the iron stored for future use.
The haem group (minus the iron) are converted to bilirubin.
Haemoglobin is broken down
Haem
Iron
Stored in liver
Bilirubin (excreted as bile pigment)
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Mrs Smith Ch21 The Delivery of Oxygen to Cells.

35. Task: Torrance-TYK pg163 Qu 1-3
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Mrs Smith Ch20: Transport Mechanisms - The Cardiac Cycle

36. Task: Torrance AYK pg163-4 Qu’s 1-4
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Mrs Smith Ch19 The need for transport