8.1.5 Recognise and draw red blood cells, monocytes, neutrophils and lymphocytes from microscope slides, photomicrographs and electron micrographs.
8.1.6 State that water is the main component of blood and tissue fluid and relate the properties of water to its role in transport in mammals, limited to solvent action and high specific heat capacity.
8.1.7 State the functions of tissue fluid and describe the formation of tissue fluid in a capillary network.
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Hold a quick round of ‘true or false’ questions to review learners’ knowledge of water and blood, for example: ‘Water is the main component of blood’ (true) and ‘Red blood cells have no contents’ (false). (F)
Learners use a microscope to examine a smear of mammalian blood and make observations of different types of blood cell. Summarise the appearance and functions of white blood cells (note that only monocytes, neutrophils and lymphocytes are required).
Learners benefit from a visual representation of the link between blood and tissue fluid. They could work in small groups to prepare a poster with a range of materials, perhaps based on a diagram of a capillary bed. Host a ‘marketplace’ to extend this activity into the next lesson. One member of each group stands by their poster and gives an explanation to other groups as they move around the room. (F)
Extension activity: Use Bloom’s taxonomy to construct five or six questions of a range of high-order thinking skills on this subject to ask learners on the subject of blood. Arrange these into envelopes, placed on the pyramid. This emphasises their challenging nature and must ask for suggestions, evaluations and justifications.
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8.2 Transport of oxygen and carbon dioxide
KC5
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8.2.1 Describe the role of red blood cells in transporting oxygen and carbon dioxide with reference to the roles of:
haemoglobin
carbonic anhydrase
the formation of haemoglobinic acid
the formation of carbaminohaemoglobin.
8.2.2 Describe the chloride shift and explain the importance of the chloride shift.
8.2.3 Describe the role of plasma in the transport of carbon dioxide.
8.2.4 Describe and explain the oxygen dissociation curve of adult haemoglobin.
8.2.5 Explain the importance of the oxygen dissociation curve at partial pressures of oxygen in the lungs and in respiring tissues.
8.2.6 Describe the Bohr shift and explain the importance of the Bohr shift.
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Provide context at the beginning of this topic to help learners appreciate its importance. For example, show a video clip of mountaineers using oxygen cylinders. Use this information to revise the reasons why cells need oxygen, and why carbon dioxide must be removed from tissues. Develop understanding by asking further questions, such as ‘What is the purpose of a red blood cell?’ (F)
Learners draw a large chalk diagram of the oxygen dissociation curve on the school playground, or they may each draw their own diagram. When you call out a specific scenario, learners should ‘jump’ to either the left or the right side of the curve. Scenarios include ‘What happens if fetal haemoglobin replaces adult?’ and ‘What happens if the pH of the blood decreases?’ Use this exercise to identify and, by repeating scenarios, correct misconceptions. (F)
Learners produce a time-lapse video using, for example, a mobile phone that shows how a model of haemoglobin (built with modelling clay) undergoes conformational changes as it circulates around the body. To extend the activity, place the model on top of an image of an individual doing intense physical activity, and use this to explain how haemoglobin tends to release some of its oxygen when carbon dioxide concentration is high – the Bohr effect. This activity makes the mechanism of oxygen transport by haemoglobin much more memorable. (I)
Learners produce a series of flash cards that have a key term from these topics on one side, and the definition on the other. They challenge their peers to provide the term or the definition when one side of the card is displayed on the desk. Good examples would be the Bohr effect and the chloride shift. (F)
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