Slide 1

Review exam questions Slide 2 http://www.youtube.com/watch?v=Qrvrs6R XxwY Slide 3 Starter - Key Word Revision Erythrocyte (RBC) Dissociation Partial pressure Oxyhaemoglobin (Hb + 4O2 HbO8 ) Biconcave Oxygen Dissociation Curve Diffusion Plasma Saturated Platelets Slide 4 Bone Marrow Blood Oxygen Association Carbon Dioxide Bohr Effect Leukocyte (WBC) Alveoli Haemoglobin Slide 5 Transport of carbon dioxide H+H+ Slide 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. Slide 7 KEY TERMS Haemoglobin Carbamino-haemoglobin Carbonic Acid Carbonic anhydrase Haemoglobinic acid (HHb) Buffer Chloride Shift Slide 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) Slide 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 3 - + H + Sequence of events in which hydrogen carbonate is formed is significant for a number of reasons Slide 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? Slide 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 Slide 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 Slide 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 3 - + 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 Slide 14 Slide 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) Slide 16 CO 2 CO 2 + H 2 O H 2 CO 3 H + + HCO 3- Conformational change Carbonic anhydrase Decreased affintiy for O 2 Slide 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 Slide 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 Slide 19 http://www.youtube.com/watch?feature=player_embedded&v=x26TWL3VKMg http://www.youtube.com/watch?feature=player_embedded&v=bklrcFuiH-8 Slide 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 Slide 21 Transport of carbon dioxide In tissue : +H2OH2OH+H+ + HCO 3 - plasma enzyme CO 2 Slide 22