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Review exam questions. XxwY.

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Presentation on theme: "Review exam questions. XxwY."— Presentation transcript:

1 Review exam questions

2 XxwY

3 Starter - Key Word Revision Erythrocyte (RBC) Dissociation Partial pressure Oxyhaemoglobin (Hb + 4O2  HbO8 ) Biconcave Oxygen Dissociation Curve Diffusion Plasma Saturated Platelets

4 Bone Marrow Blood Oxygen Association Carbon Dioxide Bohr Effect Leukocyte (WBC) Alveoli Haemoglobin

5 Transport of carbon dioxide H+H+

6 OBJECTIVES Describe the 3 ways in which carbon dioxide is carried in the blood Describe the importance of the formation of hydrogen carbonate in the carrying of carbon dioxide in the blood. Describe and explain the Chloride shift.

7 KEY TERMS Haemoglobin Carbamino-haemoglobin Carbonic Acid Carbonic anhydrase Haemoglobinic acid (HHb) Buffer Chloride Shift

8 Carbon dioxide is transported through the circulatory system in 3 ways: 1.Dissolved in plasma (5%) 2.Associated with Hb to form carbaminohaemoglobin (10%) (Changes shape of haemoglobin and encourages oxygen dissociation)

9 85% of CO 2 is transported as hydrogen carbonate ions CO2 dissolves in water to form carbonic acid (via carbonic anhydrase catalyst in RBC) CO2 + H2O  H2CO3 Carbonic acid releases H + protons (acid dissociation – chemistry) H2CO3  HCO H + Sequence of events in which hydrogen carbonate is formed is significant for a number of reasons

10 Question 1: What will happen to the nvironment within the erythrocyte? H + ions bind to Hb to form haemoglobinic acid Question 2: If Hb is absorbing H+ ions, what can we say Hb is acting as?

11 85% of CO 2 is transported as hydrogen carbonate ions H+ ions lower blood pH and combine with Hb to make haemoglobinic acid (HHb) decreasing Hb O2 affinity (Bohr) H+ + HB  HHb HCO 3 - ions diffuse out of erythrocyte. Cl - diffuse into the cell to balance the charge  CHLORIDE SHIFT Sequence of events in which hydrogen carbonate is formed is significant for a number of reasons

12 Conclusion: In a CO 2 -rich environment (i.e. at respiring tissue), more oxygen dissociates from oxyhaemoglobin Oxygen dissociation curve shifts to the right (requires higher pO 2 to saturate Hb due to H + competition) This is known as the Bohr effect

13 85% of CO 2 is transported as hydrogen carbonate ions CO 2 dissolves in water to form carbonic acid (via carbonic anhydrase catalyst in RBC) CO 2 + H 2 O  H 2 CO 3 Carbonic acid releases H + protons (acid dissociation – chemistry) H 2 CO 3  HCO H + H+ lower blood pH and combine with Hb to make haemoglobinic acid decreasing Hb O2 affinity (Bohr) H+ + HB  HHb HCO 3 - ions diffuse out of the erythrocyte. Cl - diffuse into the cell to balance the charge  CHLORIDE SHIFT Sequence of events in which hydrogen carbonate is formed is significant for a number of reasons

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15 TASK: Write equations for the following steps 1. CO 2 dissolves in water to form carbonic acid (via carbonic anhydrase catalyst in RBC) 2. Carbonic acid releases H + protons (acid dissociation – chemistry) 3. H+ lower blood pH and combine with Hb to make haemoglobinic acid decreasing Hb O2 affinity (Bohr) 4. HCO 3 - ions diffuse out of the erythrocyte & Cl - diffuse into the cell to balance the charge  CHLORIDE SHIFT EXT – Link these equations into a sequence (in a red blood cell so you can show what is & isn't inside the cell)

16 CO 2 CO 2 + H 2 O  H 2 CO 3  H + + HCO 3- Conformational change Carbonic anhydrase Decreased affintiy for O 2

17 We know that oxygen dissociates from oxyhaemoglobin where the pO 2 is low (i.e. in respiring tissue). If H+ ions can bind with Hb, they must compete with oxygen In respiring tissue: -More CO 2 produced -More Carbonic acid formed -More H + dissociated -More competition for Hb -More oxygen dissociation

18 Formation of hydrogen carbonate Build up of hydrogen carbonate ions causes them to diffuse out of RBC leaving inside of RBC positively charged. To balance electric charge Cl - ions diffuse into the RBC from plasma – this is known as the chloride shift. In this reaction Hb is acting as a buffer

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20 Breakdown of hydrogen carbonate When blood gets to the lungs, all the reactions are reversed The hydrogen carbonate and hydrogen ions recombine releasing CO 2 The chloride shift is reversed Carbamino-haemoglobin breaks down to release CO 2 CO 2 + H 2 O  H 2 CO 3  H + + HCO 3- H+ + HCO3-  H2CO3  CO2 + H2O

21 Transport of carbon dioxide In tissue : +H2OH2OH+H+ + HCO 3 - plasma enzyme CO 2

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